a novel of new charge iridium complexes for organic light
TRANSCRIPT
A NOVEL OF NEW CHARGE IRIDIUM COMPLEXES FOR
ORGANIC LIGHT-EMITTING DIODE
AND SENSOR APPLICATIONS
KATTALIYA MOTHAJIT
A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREE OF MASTER OF SCIENCE
MAJOR IN CHEMISTRY
FACULTY OF SCIENCE
UBON RATCHATHANI UNIVERSITY
ACADEMIC YEAR 2016
COPYRIGHT OF UBON RATCHATHANI UNIVERSITY
2
UBON RATCHATHANI UNIVERSITY
THESIS APPROVAL
MASTER OF SCIENCE
MAJOR IN CHEMISTRY FACULTY OF SCIENCE
TITLE A NOVEL OF NEW CHARGE IRIDIUM COMPLEXES FOR ORGANIC
LIGHT-EMITTING DIODE AND SENSOR APPLICATIONS
AUTHOR MISS KATTALIYA MOTHAJIT
EXAMINATION COMMITTEE
DR. FILIP KIELAR CHAIRPERSON
ASST. PROF. DR. RUKKIAT JITCHATI MEMBER
ASST. PROF. DR. KITTIYA WONGKHAN MEMBER
ADVISORS
…………………………………………….…… ADVISOR
(ASST. PROF. DR. RUKKIAT JITCHATI)
……………………….……………...…..... ..……………….…………….……………...…......
(ASSOC. PROF. DR. UTITH INPRASIT) (ASSOC. PROF. DR. ARIYAPORN PONGRAT)
DEAN, FACULTY OF SCIENCE VICE PRESIDENT
FOR ACADEMIC AFFAIRS
COPYRIGHT OF UBON RATCHATHANI UNIVERSITY
ACADEMIC YEAR 2016
I
ACKNOWLEDGEMENTS
Firstly, I would like to acknowledge my advisor, Asst. Prof. Dr. Rukkiat Jitchati,
for allowing me to undertake this project, all the brilliant ideas, his enthusiasm, advice
and guiding me throughout the years. Thank for his support, patience, and
encouragement throughout my graduate studies. It is not often that one finds
an advisor and colleague that always finds the time for listening to the little problems
and roadblocks that unavoidably crop up in the course of performing research.
His technical and editorial advice was essential to the completion of this dissertation
and has taught me innumerable lessons and insights on the workings of academic
research in general. His advice was most valuable to understand the obtained results
and to determine the next steps for the research presented in this thesis. Many thank to
Dr. Somboon Sahasithiwat and Miss Laongdao Menbangpung for their content advice
and sharing their extensive knowledge of OLEDs fabrication and measurement.
Thank to Asst. Prof. Dr. Kittiya Wongkhan for advice and support me in every
problem especially in English and for writing my publication. I would like
to acknowledge Dr. Filip Kielar for their constructive comment and suggestion.
Thanks Prof. Dr. Suwabun Chirachanchai and his students at the Petroleum and
Petrochemical College, Chulalongkorn University for Mass measurements in my work.
And I would also like to thank Miss Benjawan Somchob and Mr. Witsanu Sombat
for fabrication of some OLEDs presented in my work.
I would like to thank to the Organometallic and Catalytic Center (OCC), Department
of Chemistry, Faculty of Science, Ubon Ratchathani University for the synthesis
facilities.
Thanks everyone in the OCC group for contributed and helped me to make this
research work possible at Ubon Ratchathani University. And finally, I must thank my
family for their love and personal support during my study.
Kattaliya Mothajit
Researcher
II
บทคดยอ
เรอง : สารเชงซอนของโลหะอรเดยมมประจชนดใหมเพอประยกตใชเปนไดโอดเรอง อนทรยและตวตรวจวด ผวจย : แคทลยา โมทะจตร ชอปรญญา : วทยาศาสตรมหาบณฑต สาขาวชา : เคม อาจารยทปรกษา : ผชวยศาสตราจารย ดร.รกเกยรต จตคต ค าส าคญ : สารเชงซอนของโลหะอรเดยม (III), ไดโอดเรองแสงอนทรย (OLEDs), ตวตรวจวด
งานวจยนไดรายงานการสงเคราะหสารประกอบเชงซอนของโลหะอรเดยม (III) ทมประจ 2 ชด สารเชงซอนเปาหมายทงหมดไดพสจนเอกลกษณทางโครงสราง ศกษาสมบตทางแสงและสมบต ทางเคมไฟฟา ชดท 1 ใชเปนไดโอดเรองแสงอนทรย (OLEDs) ไดแก [Ir(spiro)(ppy)2]PF6 (KM01), [Ir(spiro)(thio)2]PF6 (KM02), [Ir(spiro)(difluoro)2]PF6 (KM03) และ [Ir(spiro)(ppz)2]PF6 (KM04) โดยท spiro คอ 4,5-diaza-9,9´-spirobifluorene, ppy คอ 2-phenylpyridine, thio คอ 2-thiophenyl- pyridine, difluoro คอ 2´,4´-difluorophenyl pyridine และ ppz คอ 2´,4´-difluorophenyl 1H-pyrazole น า KM01-KM04 ไปขนรปเปนอปกรณ OLEDs โครงสรางเปน ITO/PEDOT:PSS/KM01-KM04:BMIMPF6 (1:1 by mole)/TPBi/LiF/Al พบวา KM01 ใหประสทธภาพทางไฟฟา (current efficiency) สงสดท 1.72 cd/A และความสวางสงสด 2,027 cd/m2
ชดท 2 ใชเปนตวตรวจวด n-butylamine ทางส (colorimetric sensor) ไดแก [Ir(L1)(ppy)2]PF6 (NU02) และ [Ir(L2)(ppy)2]PF6 (KM09) โดยท L1 คอ dimethyl-2,2´-bipyridine-3,3´-dicarboxylate และ L2 คอ dimethyl-2,2´bipyridine-4,4´dicarboxylate จากศกษาการเปลยนแปลงสของสารละลายเชงซอนของโลหะอรเดยม พบวาเปลยนจากสแดง (528 นาโนเมตร) เปนสสม (450 นาโนเมตร) ในสภาวะกรด HCl (100 equiv.) และ n-butylamine (3 equiv.) หลงจากท าปฏกรยา 120 นาท
III
ABSTRACT
TITLE : A NOVEL OF NEW CHARGE IRIDIUM COMPLEXES FOR
ORGANIC LIGHT- EMITTING DIODE AND SENSOR
APPLICATIONS
AUTHOR : KATTALIYA MOTHAJIT
DEGREE : MASTER OF SCIENCE
MAJOR : CHEMISTRY
ADVISOR : ASST. PROF. RUKKIAT JITCHATI, Ph.D
KEYWORDS : IRIDIUM (III) COMPLEX, LIGHT EMITTING DIODE (OLEDs)
SENSOR
This study reported the synthesis of two charge iridium (III) complex series.
All of the target complexes were characterized and studied their photophysical and
electrochemical properties. In the first series, the complexes used for organic light-
emitting diode (OLEDs) were [Ir(spiro)(ppy)2]PF6 (KM01), [Ir(spiro)(thio)2]PF6
(KM02), [Ir(spiro)(difluoro)2]PF6 (KM03), and [Ir(spiro)(ppz)2]PF6 (KM04)
(spiro was 4,5-diaza-9,9´-spirobifluorene, ppy was 2-phenylpyridine, thio was
2-thiophenylpyridine, difluoro was 2´,4´-difluorophenylpyridine, and ppz was
2´,4´-difluorophenyl 1H-pyrazole). Then, KM01-KM04 were fabricated for OLED
devices based on ITO/PEDOT:PSS/KM01-KM04:BMIMPF6 (1:1 by mole)/TPBi/LiF/Al.
It was found that KM01 showed maximum current efficiency at 1.72 cd/A and
brightness at 2,027 cd/m2. In the second series, the complexes used for colorimetric
n-butylamine sensor were [Ir(L1)(ppy)2]PF6 (NU02) and [Ir(L2)(ppy)2]PF6 (KM09)
(L1 was dimethyl-2,2´-bipyridine-3,3´-dicarboxylate and L2 was dimethyl-2,2´bipyridine-
4,4´dicarboxylate). It was found that the color of charge iridium(III) complex
changed from red (528 nm) to orange (450 nm) in condition HCl (100 equiv.) and
n-butylamine (3 equiv.) after 120 minutes of reaction.
IV
CONTENTS
PAGE
ACKNOWLEDGEMENTS I
THAI ABSTRACT II
ENGLISH ABSTRACT III
CONTENTS IV
LIST OF TABLES VI
LIST OF FIGURES VII
LIST OF APPREVIATIONS XII
CHAPTER 1 INTRODUCTION
1.1 Importance in research and development 1
1.2 Organic light emitting diodes (OLEDs) application 2
1.3 Chemical sensor application 11
1.4 Objectives of thesis 12
CHAPTER 2 LITERATURE REVIEWS
2.1 Literature reviews 14
CHAPTER 3 EXPERIMENTAL
3.1 Chemical 21
3.2 Instruments and general chemical characterization techniques 23
3.3 Experimental section 25
3.4 OLEDs device fabrication 35
3.5 Colorimetric sensor study 37
CHAPTER 4 RESULTS AND DISSCUSSIONS
4.1 Synthesis of N^N ligand 38
4.2 The charged iridium(III) complex 44
CHAPTER 5 CONCLUSIONS 62
V
CONTENTS (CONTINUED)
PAGE
REFERRENCES 64
APPENDICES
A Characterized data 71
B Conference and publications 88
CURRICULUM VITAE 94
VI
LIST OF TABLES
TABLE
PAGES
2.1 Summary performance of device in OLEDs 18
3.1 Chemicals for the synthesis 22
3.2 Chemicals for OLED devices 23
3.3 Instruments for characterization technique 24
4.1 Photophysical characteristics of KM01-KM04 solution 48
4.2 Electrochemical properties and energy levels of KM01-KM04 50
4.3 Summary of host-guest multi-layer OLED performances with
configurations of ITO/PEDOT:PSS/KM01-KM04: BMIMPF6
(1:1)/TPBi/LiF/Al
52
4.4 Summary of host-guest OLED device performances with
configurations of ITO/PEDOT:PSS/KM04:BMiMPF6(1:0.75)/
TPBi/LiF/Al
54
4.5 Summary of maximum absorption wavelength of NU02
in chemical sensor
60
VII
LIST OF FIGURES
FIGURE
PAGES
1.1 General structure of neutraliridium(III) complexes 1
1.2 General structure of chargeiridium(III) complexes 2
1.3 Examples of OLEDs displays in a market 3
1.4 Chemical structures of organic small-molecules 3
1.5 Chemical structures of organometallic small-molecules 4
1.6 Chemical structures of polymers 4
1.7 Chemical structures of iridium(III) complex polymer 5
1.8 Chemical structures of dendrimer (spiro-Cz) 5
1.9 Schematic of a single layer OLED setup 6
1.10 Energy level diagram of single layer OLED device architecture 7
1.11 Schematic of a multi-layer OLED setup 7
1.12 Energy level diagram of a multilayer OLED device architecture 8
1.13 Energy level diagram of a host-guest emitter layer OLEDs device 8
1.14 The CIE 1931 color space chromaticity diagram 9
1.15 The example graph of luminescence (cd/m2) vs. voltage (V) 10
1.16 Methods for detection amine drug: (a) CCR (b) CICA (c) GC-MS 11
2.1 Structure of homoleptic iridium(III) complexes 14
2.2 Structure of the cation iridium complexes 15
2.3 Structure of the cation iridium complexes C5, C6 and C7 15
2.4 Molecular structure of fac-Ir(SFP)3 and fac-(BFP)3 16
2.5 Structure of bis-cyclometalated iridium complexes from Chen and
et al.
16
2.6 (a) Molecular structure of the iridium complex C15 and C15-Pb2+
and (b) the absorption and emission spectra of (2.0x10-5
) upon
addition of increasing amounts of Pb2+
18
2.7
(a) The proposed mechanism of the sensing reaction and
(b) the emission spectra of C16 with various amounts of Hg2+
18
VIII
LIST OF FIGURES (CONTINUED)
FIGURE
PAGES
2.8 (a) The Molecular structure and (b) the phosphorescence
spectra of iridium (III) complex C17 (10 mM) upon addition
of different anions (10eq) in CH3CN
19
2.9 (a) Molecular structure and (b) Change in the UV absorption
spectra of Ir(TBT)2(acac) on addition of Hg2+
19
2.10 (a) Molecular structure and (b) UV-vis absorption spectra of
[Ir(Bpq)2(bpy)]PF6 in CH3CN solution with various amounts
of F-. Inset: solution color observed in a CH3CN solution
of [Ir(Bpq)2(bpy)]PF6 in the absence (left) and presence
(after) of 2 equiv. of F-
20
3.1 Experimental chart model of this work 25
3.2 Cleaning process for the patterned ITO glass 35
4.1 Synthetic method of A4 38
4.2 The mechanism of oxidation reaction 38
4.3 1H NMR in DMSO-D6 of A4 39
4.4 Synthetic method of L1 precursor 39
4.5 The mechanism of esterification reaction 39
4.6 1H NMR in CDCl3 of the L1 40
4.7 The synthetic route of dimethyl-2,2´bipyridine
4,4´dicarboxylate (L2)
40
4.8 The mechanism of oxidation reaction 41
4.9 1H NMR in DMSO-d6 of YN-13 41
4.10 1H NMR in CDCl3 of L2 42
4.11 The synthetic route to N3,N
3´-dibutyl-[2,2´-bipyridine]-
3,3´-dicarboxamide (L3)
42
4.12 The mechanism of oxalyl chloride reaction
43
4.13
1H NMR in CD3OD, FTIR and MS of N
3,N
3´-dibutyl-
[2,2´-bipyridine]-3,3´-dicarboxamide (L3)
43
IX
LIST OF FIGURES (CONTINUED)
FIGURE
PAGES
4.14 Synthetic routines of the charged iridium(III) complexes
for OLEDs
45
4.15 1H NMR spectrum in CDCl3solution of KM01 46
4.16 1H NMR spectrum in CDCl3solution of KM02 46
4.17 (a) UVVis absorption spectra (b) Emission spectra of 1x10-5
M
KM01-KM04 in dichloromethane solution at room temperature
47
4.18 The picture of KM01-KM04 in dichloromethane solutions at
room temperature under normal light (left) and 356 nm UV
light (right)
48
4.19 Cyclic voltammograms of 1x10-3
M KM01-KM04 in dry
CH3CN with scan rate of 100 mV/s and 0.1 M TBAPF6 as
electrolyte
49
4.20 HOMO and LUMO distribution of the KM04 50
4.21 Structures of simple OLED devices 51
4.22 Current density and brightness versus applied bias voltage of
the device structure ITO/PEDOT:PSS/KM01-KM04:
BMIMPF6 (1:1)/TPBi/LiF/Al in acetronitrile
51
4.23 Schematics of energy level (eV) diagram of host-guest multi-
layer OLEDs using KM01-KM04 as emitter
53
4.24 CIE 1931 coordinates (x,y) and emission colour for OLED
devices of KM01-KM04 with configuration of ITO/ PEDOT:PSS/
Iridium complexes: BMIMPF6/TPBi/LiF/Al
53
4.25 Current density and brightness versus applied bias voltage of
the device structure ITO/PEDOT:PSS /KM04:BMIMPF6
(1:0.75)/TPBi/LiF/Al
54
4.26
Synthetic routines of the charged iridium(III) complexes for
sensor
55
X
LIST OF FIGURES (CONTINUED)
FIGURE
PAGES
4.27 1H NMR spectrum in CDCl3 solution of NU02 55
4.28 UVVis absorption spectra of 2x10-5
M in CH3CN of the Ir(III)
complexes at room temperature
56
4.29 The visible absorption spectra of NU02 [2.5x10-2
M] and
n-BuNH2 in CH3CN solution with excess HCl at 5, 20, 60 and
120 min (right)
57
4.30 Changes in the absorption spectra of NU02 of 2.5x10-2
M and
with 1 equiv. n-BuNH2. Inset: the reaction picture at 0 and 120
min
57
4.31 Changes in the absorption spectra of NU02 of 2.5x10-2
M and
n-BuNH2 in CH3CN solution with (A) condition 3 (1 equiv HCl),
(B) condition 4 (10 equiv HCl) and (C) condition 5 (100 equiv
HCl). Inset: the reaction picture at 0 and 120 min
58
4.32 Changes in the absorption spectra of NU02 of 2.5x10-2
M and
n- BuNH2 in CH3CN solution with 100 equiv. HCl. Inset:
the reaction picture at 0 and 120 min
59
4.33 Changes in the absorption spectra of NU02 of 2.5x10-2
M and
with 10 equiv. HCl. Inset: the reaction picture at 0 and 120 min
59
4.34 UVVis absorption spectra of NU02 and KM10 of 2.5x10-2
M
in CH3CN at room temperature. Inset: The color picture of
NU02 and KM10
60
4.35 Changes in the absorption spectra of KM09 of 2.5x10-2
M and
100 equiv. HCl in CH3CN solution with 1 equiv.n-BuNH2.
Inset: The reaction picture at 0 and 120 min
61
XI
LIST OF FIGURES (CONTINUED)
FIGURE
PAGES
A.1 13
C NMR in DMSO, ATR-FTIR (neat) and mass of A4
at room temperature
72
A.2 13
C NMR in CDCl3, ATR-FTIR (neat) of L1 at room temperature 73
A.3 13
C NMR in DMSO, ATR-FTIR (neat) and mass of YN-13
at room temperature
74
A.4 13
C NMR in CDCl3, ATR-FTIR (neat) and mass of L2 at room
temperature
75
A.5 13
C NMR in DMSO, ATR-FTIR (neat) and mass of L3 at room
temperature
76
A.6 ATR-FTIR (neat) and mass of KM05 at room temperature
77
A.7 ATR-FTIR (neat) and mass of KM06 at room temperature 78
A.8 ATR-FTIR (neat) and mass of KM07 at room temperature 79
A.9 ATR-FTIR (neat) and mass of KM08 at room temperature 80
A.10 ATR-FTIR (neat) and mass of NU02 at room temperature 81
A.11 ATR-FTIR (neat) and mass of KM09 at room temperature 82
A.12 ATR-FTIR (neat) and mass of KM10 at room temperature 83
A.13 13
C NMR in CDCl3, ATR-FTIR (neat) and mass of KM01
at room temperature
84
A.14 13
C NMR in CDCl3 and ATR-FTIR (neat) of KM02
at room temperature
85
A.15 13
C NMR in CDCl3, ATR-FTIR (neat) and mass of KM03
at room temperature
86
A.16 13
C NMR in CDCl3, ATR-FTIR (neat) and mass of KM04
at room temperature
87
XII
LIST OF ABBREVIATIONS
ABBREVIATION
FULL WORD
A Absorbance
AR. Analysis reagent
anh. Anhydrous
Aq. Aqueous
B Brightness
13C NMR Carbon nuclear magnetic resonance
cm
Centimeter
cm-1
Reciprocal centimeter (unit of wavenumber)
cm3 Centimeter cubic unit
δ Chemical shift in ppm relative to tetramethylsilane
CIE Commission Internationale de L’Eclairage or
International Commission on Illumination
conc. Concentrated
J Coupling constant (for NMR spectral data)
CE Current efficiency (cd/A)
CV Cyclic voltammetry
oC Degree Celsius
DI
Deionized Water
DFT Density functional theory
DCM Dichloromethane
DMSO Dimethyl sulfoxide
d Doublet (for NMR spectral data)
dd Double of doublet (for NMR spectral data)
ETL Electron transport layer
eV Electron volt
ESI-MS Electrospray ionization mass spectrometry
EML Emitting layer
XIII
LIST OF ABBREVIATIONS (CONTINUED)
ABBREVIATION
FULL WORD
Eg Energy gap
EtOAc Ethyl acetate
EQE External Quantum Efficiency
FTIR Fourier transform infrared spectroscopy
Hz Hertz
HOMO Highest occupied molecular orbital
HTL Hole transport layer
h Hour
ITO Indium-tin-oxide
LUMO Lowest unoccupied molecular orbital
IR Infrared
MS Mass spectroscopy
MHz Mega hertz
MLCT Metal to ligand charge transfer
mmol Milimole
mA Milli ampare
ml Milliliter
mmol Milimole
mV Millivolt
Min Minutes
Molar absorptivity
M Molarity
Mw Molecular weight
Mol Moles
m Multriplet (for NMR spectral data)
nm Nanometers
NMR Nuclear magnetic resocence
XIV
LIST OF ABBREVIATIONS (CONTINUED)
ABBREVIATION
FULL WORD
Ohm
OLED Organic light-emitting diode
Eox Oxidation potential
ppm Parts per million
ppy Phenylpyridine
PL Photoluminescence
PE Power efficiency (lm/W)
Ered Reduction potential
Rt Room temperature
s Singlet (for NMR spectral data)
m2 Square meter
TMS Tetra methylsilane
t Triplet (for NMR spectral data)
UV-Vis Ultra violet-visible
V Voltage
v/v Volume/volume
1
CHAPTER 1
INTRODUCTION
1.1 Importance in research and development
Heavy-metal complexes with phosphorescent emission are the important
luminescence materials [1-6], different from conventional fluorescent materials, which
are the triplet-state transition. Being among the best class of phosphorescent
heavy metal complexes, iridium(III) complexes are well known for their rich
photochemical and photophysical properties [7-9] due to their relatively short-excited
state lifetimes, high luminescence efficiencies [10], and excellent color tuning from blue
to the near-infrared region upon modification of the ligand [11,12] or by introducing
a variety of electron donors or acceptors into the ligand [13].
The iridium complex can be divided two structures namely the neutral iridium(III)
complexes and charged iridium(III) complexes.
Firstly, the neutral iridium(III) complexes, its structure compose of three
cyclometallating ligands (C^N), for example acetonylacetonate (acac), 2-phenylpyridine
(ppy) and difluorophenyl pyridine (dFppy) with anionic counter ion shown in Figure 1.1.
Figure 1.1 General structure of neutral iridium(III) complexes
2
Secondly, the charged iridium(III) complex, its structure compose of two C^N ligands
and a neutral N^N ligands such as bipyridine (bipy) and phenanthroline (phen) derivatives.
The charged iridium(III) complexes; (C^N)2Ir(N^N)PF6 are shown in Figure 1.2.
Figure 1.2 General structure of charge iridium(III) complexes
Phosphorescent light emitting materials have been used successfully in highly
efficient OLEDs [14,15] compared with fluorescent light emitting materials which
only singlet state excitons can emit the light. The phosphorescent light emitting
materials are efficient as both singlet and triplet excitons [16,17]. These complexes
have been explored for a multitude of photonic applications including organic
light-emitting diodes (OLEDs) [18,19] and biological labeling reagents [20].
Moreover, the iridium(III) complexes also have mainly focused on the new
chemosensors [14]. Moreover, the emission wavelength, lifetime and quantum
efficiency of this kind of phosphorescent material can be fine-tuned through
the modification of ligand structures and metal center.
1.2 Organic light emitting diodes (OLEDs) application
Prior to the OLEDs, display technology has been underwent a significant revolution.
The cathode ray tube (CRT), plasma display (PMD), liquid crystal display (LCD),
light emitting diode were used in the display market. All these displays have their own
limitations including bulkiness, low viewing angle, color purity, etc. The essential
requirements of next generation displays technology are reproduction of brightness,
3
pure color, high resolution, low weight, thin screen, reduction in cost and low power
consumption which are organic light-emitting diodes (OLED) display technology [21]
such as LG OLED TV, OLYMPUS STYLUS TG-2 and Dell Thunder shown in Figure 1.3.
55’’ OLED TV STYLUS TG-2 Dell Thunder
Figure 1.3 Examples of OLEDs displays in a market
1.2.1 Materials for OLEDs
OLED materials can be broadly classified as small (organic) molecules,
polymers and dendrimers.
Since the first report of multi-layered organic light-emitting diodes (OLEDs)
using small molecule by Tang and Van Slyke [22], Electroluminescence device
has been developed remarkably because they have used applications in full color flat panel
display [23-25]. They are semicrystalline or crystalline materials with high aqueous
solubility. The example of small organic material e.g. isrubrene, porphyrine, coumarin
and perylene are shown in Figure 1.4.
Figure 1.4 Chemical structures of organic small-molecules
4
In addition, several groups have reported the organometallic small molecules
composed of the metal centered atom and ligands as shown in Figure 1.5.
Figure 1.5 Chemical structures of organometallic small-molecules
The light emission color of the polymers strongly depends on the type of
the polymer, its chemical composition and the nature of side groups. Hence, by chemical
modification of the polymer structure, polymers can emit in ranging from 400 nm
to 800 nm. Another benefit of polymer is the incorporation with a small molecule
which influences the emission color of light-emitting polymers. By adding a small
amount of a suitable dye to a polymer, energy can be transferred from the polymer.
The color from the device can be tuned using different dyes. The example of organic
polymers as shown in Figure 1.6 and neutral iridium(III) complex polymer [26]
as shown in Figure 1.7.
Figure 1.6 Chemical structures of polymers
5
Figure 1.7 Chemical structures of iridium(III) complex polymer
Dendrimers generally consist of a central core, to which one or more
branched dendrons are attached. Surface groups attached to the distal end to provide
the solubility, which is necessary for solution processing. The dendritic structure
allows independent modification of the core (light emission), branching groups
(charge transport) and surface groups (processing properties). The example of spiro-Cz
dendrimer [27] is shown in Figure 1.8.
Figure 1.8 Chemical structures of dendrimer (spiro-Cz)
6
1.2.2 OLEDs structure and mechanism operation
In general, the basic OLED structure consists of a stack of emitting layers
sandwiched between a transparent conducting anode and metallic cathode.
After an appropriate bias is applied to the device, holes are injected from the anode
and electrons from the cathode. Then, the recombination events between the holes and
electrons result in electroluminescence (EL). This device called a single layer device;
however, there is sometimes difficulty in injecting carriers into the emitting layer.
To solve this problem, the structure was included with an electron transport layer
(ETL) and a hole transport layer (HTL) to balance charge and hole in the device.
This type called a multi-layer OLEDs device.
1.2.2.1 Single layer devices
Single layer architecture is the simplest OLED which is shown in
Figure 1.9. In this case the organic emitter is coated between the metal cathode and the
semiconductor anode. The organic emitter acts as an emitter and charge transport
material (holes and electrons) at the same time. The anode, indium-tin-oxide (ITO)
is used in most case. A thin semitransparent ITO layer is sputtered onto a glass
substrate. Afterwards, the emitting layer is deposited either by liquid phase
or evaporation techniques onto the ITO anode. Finally, metal cathode for example Al,
Ca and Mg is evaporated on top of the OLED substrate. A suitable cathode material
should a low work function in order to ensure efficient electron injection into
the organic semiconductor.
Figure 1.9 Schematic of a single layer OLED setup
After a voltage is applied to the electrode shown in Figure 1.9,
electrons from the cathode and holes from the anode are injected into the organic
semiconductor. Due to the electric field between the two electrodes, the positive and
7
negative charge carriers move through the organic emitting layer. As soon as they
recombine in the emitting material which called “exiton” and light is generated.
The energy level diagram of a single layer OLED is shown in Figure 1.10.
Figure 1.10 Energy level diagram of single layer OLED device architecture
1.2.2.2 Multi-layer devices
The OLED performance is determined by the number of charge
carriers that are injected the number of holes and electrons that actually recombine
under emission of light. The materials used in single layer devices are usually better
hole than electron conductors. As the holes are moving faster through the emitting
layer than electrons, the recombination zone shifted towards the cathode what usually
leads to a non-radiative loss of energy. Consequently, the efficiency decreases.
In order to improve device efficiency, the multi-layer architecture
was introduced as shown in Figure 1.11. The additional of the injection and transport
properties for holes and electrons should be similar to obtain a perfect charge carrier
balance which can improve the efficiency of the device. Therefore it is usually
necessary to use complex device architecture.
Figure 1.11 Schematic of a multi-layer OLED setup
8
In general working principles of multilayer shown in Figure 1.12,
a voltage is applied to the electrodes due to the electric field between the two electrodes.
The positive carriers move to the HTL and negative charge to ETL. The electrons and
holes are transfer into organic emitting layer. As soon as they recombine
in the emitting material which called “exiton” and light is generated [21].
Figure 1.12 Energy level diagram of a multilayer OLED device architecture
To improve a better performance and long term stability a modified
emitting layer was used called the host-guest system simplified in Figure 1.13.
The key parameter of this device is the energy matching of a host and a guest
especially in the emitting layer. The HOMO and LUMO levels of a host have a wider
energy band gap than the guest. Then the energy transfer can be progressed [21].
Figure 1.13 Energy level diagram of a host-guest emitter layer OLEDs device
9
1.2.3 Key parameters of the OLEDs
A key point in OLED development for full-color display application
is establishment of a set of red, green, and blue emitter (RGB) with higher
efficiencies, enhanced brightness, color purity and improved lifetime of optoelectronic
devices. Therefore, intensive research efforts in organic materials design and device
architectures are ongoing. The CIE chromaticity coordinates system as shown in
Figure 1.14 the method to define the chromaticity of a light source, will be used
throughout this thesis, since it is the preferred standard in the display and lighting
industries [28-31]. This method originally recommended in 1931 by the CIE defines
all metameric pairs by giving the amounta X, Y, Z of three imaginary primary colors
required by a standard observer to match the color being specified.
Figure 1.14 The CIE 1931 color space chromaticity diagram
The parameters for evaluation of the OLED performances in this work
are luminance, current efficiency, power efficiency and CIE coordinate. Therefore,
these terms and the others are described in this section.
1.2.3.1 Luminance (L)
In general, “brightness” is an expression of the amount of light
emitted from a surface per unit of area. It is called “luminance”, which is expressed as
candelas per square meter (cd/m2) of light emitting surface. For example, the luminance
of a incandescent light bulb is about 10,000 candelas per square meter. The luminous
intensity is defined as the emission in cd/m from the emitting surface therefore
the high luminous value means the device are much brighter as well.
10
1.2.3.2 Luminous efficiency (LE)
The luminous efficiencyof a source is a measure of the efficiency
which the source provides visible light from electricity. Luminous efficiency is measured
in candelas per ampere (cd/A). LE is calculated from this below equation [32-33].
Luminous efficiency =
Where L is the luminescence and j is the current density
(current/active area, mA/m2).
1.2.3.3 Luminous power efficiency (PE)
The luminous power efficiency is the amount of light emitted from
a source per voltage from electricity. Power efficiency is measured in lumens per watt
(lm/W). PE can be determined using the following equation [33]
Power efficiency =
Where L is the luminescence, j is the current density and V is the
applied voltage.
1.2.3.4 Turn on voltage
Turn on voltage is the begin brightness point at the low voltage in
OLEDs device. The graph plots between luminescence (cd/m2) vs. voltage (V) shown
in Figure 1.15.
Figure 1.15 The example graph of luminescence (cd/m2) vs. voltage (V)
Turn on voltage
11
1.3 Colorimetric sensor application
Phosphorescent heavy-metal complexes as a colorimetric sensor and biological
labeling reagent have attracted increasing interest due to their advantageous
photophysical properties.
The iridium(III) metal center can coordinate with various C^N cyclometalating
and N^N ligands to give a wide range of complexes with very interesting physical and
chemical properties. Some of these complexes have been utilized as a sensor for various
analytes, including metal cation, anions, pH and oxygen [34]. We anticipate that
this class of complexes can be developed as a new generation of colorimetric sensor
reagents because of their intense and high stability.
The organic amine bases such as amphetamine, methamphetamine and heroin are still
the problem of drug abuse. Structures of organic amine bases are shown below,
which is the primary amine, secondary amine and tertiary amine, respectively.
The methods for detection amine drugs can be divided into three methods called
chemical color reaction (CCR), color immunochromatographic assay (CICA) and
gas chromatography-mass spectrometry (GC-MS) according to the efficiency and
specificity. The three methods for detection amine drugs are shown in Figure 1.16.
(a) CCR (b) CICA (c) GC-MS
Figure 1.16 Methods for detection amine drug: (a) CCR (b) CICA (c) GC-MS
12
The first method has proved to be a convenient, simple and cheap. However,
this method has the less accuracy compared to the others. The second method is CICA,
the method has accurate than the CCR technique and confirm the results from the first
method. The third method, GC-MS has high accuracy and high specificity.
It has high costs and takes a long time for analysis compared to the others.
Additionally, a few types of phosphorescent iridium(III) complexes have been
reported as a amine CCR. It is well known that the photophysical properties of iridium(III)
complexes are dependent on the chemical structures of ancillary ligands [18]. When the
ancillary ligands of an iridium(III) complex contains a specific component to interact
with the analyte, the presence of this analyte leading to dramatic changes in
the photophysical properties of the iridium(III) complex.
1.4 Objectives of thesis
1.4.1 To synthesize N,N-bidentate ligands
1.4.2 To synthesize dimeric iridium complexes
13
1.4.3 To synthesize charged iridium(III) complexes
1.4.4 To characterize the molecular structure of the target complexes by 1H and
13C NMR, Fourier transforms infrared spectroscopy (FT-IR) and mass spectroscopy (MS)
1.4.5 To study the optical property of charged iridium complexes by UV-Visible
spectroscopy and fluorescence spectroscopy
1.4.6 To study the electrochemical property of charged iridium complexes (KM01,
KM02, KM03 and KM04) by cyclic voltammetry (CV)
1.4.7 To fabricate and investigate the OLEDs devices with KM01, KM02, KM03
and KM04
1.4.8 To study potential of our complexes for colorimetric n-butylamine sensor with
NU02, KM09 and KM10
CHAPTER 2
LITERATURE REVIEWS
2.1 Literature reviews
Organic light-emitting diodes (OLEDs) based on iridium (III) complexes is great
interest for application in display technology. Many research groups have been
intensive studied and designed of new materials leads to high efficiency, brightness,
lifetime and stable the color of optoelectronic.
In 1991, Watts and coworker [35] synthesized several substituted 2-phenylpyridine
which fac-Ir(ppy)3, C1, C2, and C3 for studying their photophysics. The parent
compound fac-Ir(ppy)3 shows a maximum emission wavelength at 494 nm, (77 K)
in ethanol/methanol (Figure 2.1). They focused that complex C1 with an electron
withdrawing group (F) exhibits 26 nm blue shift compared to fac-Ir(ppy)3.
In the opposite way, C3 with its electron donating group (OCH3) shows 45 nm red shift.
It is interesting to note the difference between the complex C2 and C3,
which is simply the effect of the position of the electron donating substitution on
the phenyl ring.
Figure 2.1 Structure of homoleptic iridium(III) complexes [35]
In 2010, Lei and coworker [36] synthesized the cationic iridium complex, Irdf-pyim
and Ir-pyim (Figure 2.2), in which cyclometalated 2-phenylpyridine and cyclometalated
2-(2,4-difluorophenyl) pyridine ligands. They tune light emission color from
blue green to red.
15
Figure 2.2 Structure of the cation iridium complexes [36]
The iridium (III) complexes such as C5, C6 and C7 [37] (Figure 2.3) were developed
by 4,5-diaza-9,9’-spirobifluorene as N^N ancillary ligands, in which one (C6) or two (C7)
phenyl groups. The photoluminescence of all the complexes exhibited maxima emission
in the range of 500 and 505 nm. The X-ray crystal structures of complexes C6 and C7
show that the pendant phenyl ring forms strong intramolecular face-to-face -stacking
with the difluorophenyl ring of the cyclometalated ligand with distances of 3.38 Å
for complex C6 and 3.46 Å for complex C7, respectively. The device characteristics
based on the structure of ITO/PEDOT:PSS/Complex C5 or C6 or C7/Al. They found that
the brightness can be increased to 10.6 cdm-2
with EQE value of 1.43% (for devices C7)
which explained by the minimization of -stacking interaction in the light-emitting
electrochemical call (LEC) devices.
Figure 2.3 Structure of the cation iridium complexes C5, C6 and C7 [37]
In 2010, Huang and coworkers [38] synthesized spiro-functionalized ligand
of the iridium complex fac-Ir(SFP)3 and fac-(BFP)3 which the steric hindrance
16
originates from the combination of rigid (Figure 2.4) and bulky three-dimensional (3D)
moieties. Devices were fabricated with a configuration of ITO/NPB (40 nm)/Ir(SFP)3
or Ir(BFP)3 doped CBP/BCP/Alq3 (10 nm)/LiF/Al. They found that the fac-Ir(SFP)3
exhibits impressive higher quantum yields at 10.0% more than alkyl-substituted
fac-(BFP)3 at 1.1%. The lower turn-on voltage and higher optimized dopant
concentration for fac-Ir(SFP)3 were observed. The phosphorescent organic
light-emitting diodes (PHOLEDs) exhibited a higher maximum brightness (Lmax) of
35,481 cd m-2
at 21.3 V, current efficiency of 44.3 cdA-1
, and power efficiency of
34.8 mW-1
. The both iridium complex display yellow-orange color with commission
international del'Eclairage (CIE) coordinates of (0.41, 0.56) and (0.42, 0.54), respectively.
Figure 2.4 Molecular structure of fac-Ir(SFP)3 and fac-(BFP)3
In addition bis-cyclometalated iridium(III) complexes based on structure of
spirobifluorene ligands were designed to iridium complexes (C11) (Figure 2.5).
Figure 2.5 Structure of bis-cyclometalated iridium complexes from Chen and
et al. [39]
17
The device configuration is ITO/PEDOT:PSS (50 nm)/PVK (50%):PBD (40%):
C11 (10%) (45 nm)/TPBi (40 nm)/LiF (0.5 nm)/Ca (20 nm)/Ag (150 nm).
The devices showed intense yellow emission in the range of 554 nm. Complex C11
achieved efficiency of 36.4 cd/A (10.1%) at 198 cd/m2 and maximum brightness
30,956 cd m-2
at 20 V.
From the previous literatures, OLEDs performance can be summarized in Table 2.1.
Table 2.1 Summary performance of device in OLEDs
Ir Complex Vturn-on
(V)
Bmax
(cd/m2)
CEmax
(cd/A)
PEmax
(lm/W)
CIE
(x, y)
Irdf-pyima
Ir-pyima
C5b
C6 b
C7 b
fac-Ir(SFP)3c
fac-Ir(BFP)3 c
C11d
6.9
4.0
-
-
-
3.7
5.2
5.8
890
11,500
25.4
5.76
10.6
35,481
20,196
30,956
0.6
4.1
2.13
3.37
4.25
44.3
24.2
36.4
-
-
1.9
3.1
3.9
34.8
11.1
-
0.21, 0.38
0.35, 0.56
0.23, 0.47
0.28, 0.50
0.28, 0.54
0.41, 0.56
0.42, 0.54
0.46, 0.52
a ITO/ PEDOT:PSS/PVK:OXD-7 or PBD:complexes/Cs2CO3/Al; OXD-7
for Irdfpyim and PBD for Ir-pyim [36]
b PEDOT:PSS/ITO/C5 or C6 or C7 with ionic liquid/Al [37]
c ITO/NPB/Ir(SFP)3 or Ir(BFP)3-doped CBP/BCP/Alq3/LiF/Al [38]
d ITO/PEDOT:PSS/PVK:PBD:C11/TPBI/LiF/Ca/Ag [39]
The photophysical properties of iridium(III) complexes are dependent
on the chemical structures of ancillary ligands. Which the ancillary ligand of an
iridium(III) complex contains a specific component to interact with the analyte,
the presence of this analyte can lead to dramatic changes in the photophysical properties
of the iridium(III) complex. Therefore, many research groups have been studied and
developed iridium (III) complexes to biological labeling reagents due to their high
luminescence quantum yields and long-lived excite.
18
Chi and coworkers [40] synthesized C15 which the iridium(III) bears two
cyclometalated and N-phenyl pyrazoles. They demonstrated the Pb2+
cation sensing
using the emissive spectra of C15 at room temperature. The phosphorescence upon
forming C15-Pb2+
can be confirmed by X-ray structural analyses as shown in Figure 2.6.
Figure 2.6 (a) Molecular structure of the iridium complex C15 and C15-Pb2+
and
(b) the absorption and emission spectra of (2.0 x 10-5
) upon addition of
increasing amounts of Pb2+
[40]
Lu and coworkers [41] synthesized a cyclometalated iridium complex,
Ir(dpci)2(dtc). It is called C16. The photoluminescence spectrum of C16 shows
maximum emission at 686 nm. C16 containing a dithiocarbamate ancillary ligand
can serve as a highly selective for Hg2+
. The emission spectra titration of C16 with
Hg2+
was also measured. It was found that the emission increases continuously until
the addition of 1 equiv. of Hg2+
(Figure 2.7). They explained by the elimination
of the dithiocarbamate ancillary ligand.
Figure 2.7 (a) The proposed mechanism of the sensing reaction and
(b) the emission spectra of C16 with various amounts of Hg2+
[41]
(a) (b)
(a) (b)
19
In 2014, Hyun and coworkers [42] synthesized C17 for phosphorescence
chemosensors for H2PO4-. The complex contained two preorganized urea groups
for the recognition of H2PO4- are shown in Figure 2.8.
Figure 2.8 (a) The Molecular structure and (b) the phosphorescence spectra
of iridium (III) complex C17 (10 mM) upon addition of different
anions (10eq) in CH3CN [42]
In 2012, Huang and coworker [43] synthesized a neutral iridium (III) complex
Ir(TBT)2(acac) based on 2-thiophen-2-yl-benzothiazole (TBTH) ligands containing
four sulfur atoms are shown in Figure 2.9 (left). Upon addition of Hg2+
to the solution,
the absorption band at 480 nm disappears progressively, while the absorption band
at 405 nm gradually increased. The color of the solution changed from orange to yellow,
in Figure 2.9 (right). The stoichiometry of Ir(TBT)2(acac) is given by the variation
of absorbance at 405 nm or absorbance 480 nm with respect to equivalents of added Hg2+
.
Figure 2.9 (a) Molecular structure and (b) Change in the UV absorption spectra
of Ir(TBT)2(acac) on addition of Hg2+
(a) (b)
(a) (b)
20
Huang and coworker [44] synthesized the iridium(III) complex [Ir(Bpq)2(bpy)]PF6
based on cyclometalated ligands (Bpq) containing a dimesitylboryl group.
Considering the significant response of ligand Bpq to F-, it is reasoned that
the photophysical and electrochemical properties of [Ir(Bpq)2(bpy)]PF6 could be
affected upon the addition of F-. The absorption shows the variation in the absorption
spectra of [Ir(Bpq)2(bpy)]PF6 upon the addition of F-. After F
- was added to a solution
of [Ir(Bpq)2(bpy)]PF6 the absorbance at 290 and 350 nm decreased gradually whereas
the absorbance at 400 nm increased, corresponding to an isobestic point at 379 nm.
Importantly, the absorption band in the range of 420-600 nm was red-shifted with
an increase in the absorbance, corresponding to a change in the solution color from
yellow to orange-red, in Figure 2.10 (inset), indicating that [Ir(Bpq)2(bpy)]PF6 can
serve as a “nakedeye” indicator of F-.
Figure 2.10 (a) Molecular structure and (b) UV-Vis absorption spectra of
[Ir(Bpq)2(bpy)]PF6 in CH3CN solution with various amounts of F
-.
Inset: solution color observed in a CH3CN solution of
[Ir(Bpq)2(bpy)]PF6 in the absence (left) and presence (after) of
2 equiv of F-
(a) (b)
CHAPTER 3
EXPERIMENTAL
3.1 Chemicals
All the chemicals used in this thesis are shown in Table 3.1 and Table 3.2
Table 3.1 Chemicals for the synthesis
Chemicals Formula Grade Manufacturer
Acetonitrile
n-Butylamine
Dichloromethane
Hydrochloric acid
Iridium(III) chloride hydrate
Methanol
4,4'dimethyl2,2´Bipyridine
Oxalyl chloride
1,10-Phenanthroline
Potassium hexafluorophosphate
Potassium hydroxide
Potassium permanganate
Pyridine
Sodium dichromate
Sodium hydroxide
Sodium sulfate
Sulfuric acid
Tetrahydrofuran (THF)
Toluene
CH3CN
C4H9NH2
CH2Cl2
HCl
IrCl3.xH2O
CH3OH
C12H12N2
(COCl2)2
C12H8N2
KPF6
KOH
KMnO4
C5H5N
Na2Cr2O7
NaOH
Na2SO4
H2SO4
C4H8O
C6H5CH3
ACS-for analysis
98%
ACS-for analysis
37%, for analysis
Hygroscopic
ACS-for analysis
99%
98%
ACS-for analysis
99%, extra pure
EKA pellets
AR
ACS-for analysis
99.5%
ACS- for analysis
ACS- for analysis
96% AR. Grade
ACS- for analysis
ACS- for analysis
CARLO ERBA
Fluka
CARLO ERBA
CARLO ERBA
Precious Metals
Online
CARLO ERBA
Acros organic
Acros organic
CARLO ERBA
Acros organic
CARLO ERBA
CARLO ERBA
CARLO ERBA
Aldrich
CARLO ERBA
CARLO ERBA
CARLO ERBA
CARLO ERBA
CARLO ERBA
22
Table 3.2 Chemicals for OLED devices
Chemicals Formula Grade Manufacturer
Acetone
Acetonitrile
Aluminum
1-Butyl-3-methylimidazolium
hexafluorophoaphate (BMIMP)
1,2-Dicholobenzene
Dichloromethane (DCM)
Ethanol
2-Propanol
Poly(methyl methacrylate)
Poly(3,4-ethylenedioxy-
thiophene)polystyrene
sulfonate
1,3,5-Tris(N-phenyl-
benzimidizol-2-yl)benzene
(TPBi)
Indium doped tin oxide (ITO)
glass 15Ω
CH3COCH3
CH3CN
Al
C8H15F6N2P
C6H5Cl2
CH2Cl2
CH3CH2OH
C3H7OH
(C5O2H8)n
C45H30N6
C14H11O5S2
-
ACS-for analysis
ACS-for analysis
Powder
98%
ACS-for analysis
ACS-for analysis
ACS-for analysis
ACS-for analysis
Premium Denture
Acrylic
Clevios P
VP.AI4083
99 %
Size 2.5x2.5 cm
CARLO ERBA
CARLO ERBA
Acros organic
Acros organic
CARLO ERBA
CARLO ERBA
CARLO ERBA
CARLO ERBA
LANG
H.C.Starck
Lumtec
Lumtec
23
3.2 Instruments and general chemical characterization techniques
3.2.1 Instruments for characterization
The general instruments used in the characterization are shown in Table 3.3
Table 3.3 Instruments for characterization technique
Instruments Model Company
Fourier Transform Infrared
Spectrometer (FT-IR)
UV-Visible Spectrometer (UV)
Nuclear Magnetic Resonance
(NMR)
Cyclic Voltammetry (CV)
Mass Spectroscopy (MS)
Melting point Apparatus (m.p.)
Fluorescence spectrometer
Ultrasonic cleaner
UVO cleaner
Spin-coater
Vacuum oven
Thermal evaporator
Luminance detector
Power supply and multimeter
Spectrum Two
V-650 spectrophotometer
Bruker ADVANCE,
300 MHz
AutolabMetrohm PG11
Micro TOF II
-
630
LS 50B
42-220
P6206
VD23
AUTO306
LS-110
2420
Perkin Elmer
Jasco
Perkin Elmer
Metro
Bruker
Buchi
Perkin-Elmer
Crest
Jelight
Specialty coating
systems
Binder
Edwards
Minolta
Keithley
3.2.2 General chemical characterization techniques
The chemical were used without further purification whereas dried solvent for
example toluene, pyridine and THF.
The structural of N,N-bidentate ligands, dimeric iridium(III) complexes and
charged iridium complexes were characterized by 1H,
13C NMR, melting point and FT-IR
techniques. The optical and electrical properties of the charge iridium(III) complexes were
characterized by UV-Visible spectroscopy and cyclic voltammetry, respectively.
24
3.2.2.1 Fourier Transform Infrared Spectroscopy (FT-IR)
Infrared (FT-IR) spectra were recorded with a Fourier transform
infrared spectrophotometer over the 4000 - 400 cm-1
range, at 16 nm/s scaning rate.
Data for FT-IR spectra are reported as follows: frequency (cm-1
).
3.2.2.2 UV-Visible spectroscopy
UV-Visible spectra were measured in a 1 cm path length quartz cell
using a V-650 spectrum high resolution UV-Vis for new charge iridium(III) complexes.
The samples were dissolved in dichloromethane, acetonitrile and diluted to
a concentration 2x10-5
M at room temperature.
3.2.2.3 Nuclear magnetic resonance (NMR)
1H and
13C NMR spectra were performed in CDCl3, DMSO-D6
or CD3OD recorded on 300 MHz spectrometer, using TMS as the internal reference.
Data for NMR spectra are reported as followed: chemical shift (δ ppm), multiplicity,
coupling constant (Hz) and integration (number).
3.2.2.4 Cyclic voltammetry (CV)
Cyclic voltammetry was conducted on a Metrohm PG11. The 1x10-3 M
solutions of the corresponding complexes were prepared in dichloromethane and
acetonitrile containing 0.1 M tetrabutylammoniumhexafluorophosphate ([Bu4N]PF6)
as supporting electrolyte, and purged with nitrogen gas for 60 min prior to use
at a scan rate of 100 mV/s at room temperature. The working electrode was a glassy
carbon electrode. The auxiliary electrode was a Pt electrode, and Ag/AgCl (3 M KCl)
electrode was used as reference electrode.
3.2.2.5 Mass spectroscopy
Molecular weight of charge iridium(III) complexes was measured
on Bruker, by Electrospray ionization Mass Spectroscopy (ESI-MS) techniques with
position mode.
3.2.2.6 Melting point apparatus (m.p.)
Melting points was measured on Buchi 530 scientific melting point
apparatus in open capillary method and are uncorrected and reported in degree
Celsius.
25
3.3 Experimental section
This experimental section part gives a summarized description of the synthesis
of the charge iridium(III) complexes for organic light-emitting diode (OLEDs)
and colorimetric n-butylamine sensor. It is divided in five main steps. First step is
the N^N ligand synthesis. Second step is the dimeric iridium complex synthesis.
Third step is the charge iridium(III) complex synthesis. Fourth to fifth steps are
the characterization and electrochemical studied and performance of OLEDs devices,
respectively. The overall experimental flow chart is shown in Figure 3.1.
Figure 3.1 Experimental chart model of this work
3.3.1 Synthesis of N^N ligand
3.3.1.1 The synthesis of dimethyl-2,2´-bipyridine-3,3´-dicarboxylate (L1)
Performance study of OLEDs
(KM01, KM02, KM03, KM04)
Application for amine sensor
(NU02, KM09, KM10)
Optical and electrochemical studies
Characterized by NMR, FT-IR, mass techniques
Charged iridium(III) complex synthesis
N^N ligand synthesis
(L1, L2 and L3)
Dimeric iridium complex synthesis
(KM05, KM06, KM07 and KM08)
26
1,10-Phenanthroline (1.00 g, 6 mmol) was dissolved in 75 ml of 0.12 M
potassium hydroxide and the mixture was heated to form a homogenous solution.
The 0.40 M aqueous potassium permanganate (40 ml) was slowly added to this
reaction mixture. The reaction was refluxed with stirring for 3 h. Then, the solid
was filtered to get an orange solution and cooled to room temperature followed by
extraction with dichloromethane (30 ml x 3). The aqueous layer was added with
conc. hydrochloric acid. After that, the crude product was evaporated to dryness to get
the product as 2,2'-bipyridine-3,3'-dicarboxylic acid (A4) (2.30 g, 97 %); m.p. 264 ºC
(decomposed); 1H NMR (300 MHz, DMSO-D6) δ 8.73 (d, J = 4.9 Hz, 2H), 8.35 (s, 2H),
7.67-7.54 (d, J = 4.8 Hz, 2H); 13
C NMR (75 MHz, ) δ 167.2, 158.6, 150.8, 138.6,
127.1, 123.5; ATR-FTIR (neat) 3397, 3071, 2573, 1726, 1623, 1395, 1220, 1065 cm-1
;
MS (ESI) m/z calcd for C12H8N2O4 (M-H+) 243.0406, found 243.0313.
The mixture of A4 (1.00 g, 4.1 mmol), 1 ml of conc. sulfuric acid
and 20 ml of methanol were refluxed for 24 h. The reaction mixture was cooled
to room temperature. Then the neutral solution was adjusted with sodium hydroxide
and extracted with dichloromethane (30 ml x 3). The organic layer was dried with
anhydrous sodium sulfate. The crude reaction was evaporated to dryness and
then passed through silica column chromatography using 5% MeOH:DCM to get
the target product L1 as colorless solid (0.49 g, 45 %); m.p.140 oC;
1H NMR
(300 MHz, CDCl3) δ 8.79 (dd, J = 4.9, 1.5 Hz, 2H), 8.40 (dd, J = 8.0, 1.5 Hz, 2H),
7.54 - 7.40 (dd, J = 8.0, 5.0 Hz, 2H), 3.70 (s, 6H); 13
C NMR (75 MHz, ) δ 165.9,
159.4, 151.5, 138.1, 125.3, 122.6, 52.2; ATR-FTIR (neat) 3004, 1711, 1599, 1412,
1296 and 1131 cm-1
; MS (ESI) m/z calcd for C14H12N2O4 (M+H+) 273.0875, found
273.0870.
3.3.1.2 The synthesis of dimethyl-2,2´bipyridine-4,4´dicarboxylate (L2)
Na2Cr2O7 (1.35g, 8.69 mmol) was added to 25 ml of conc. H2SO4
in 100 ml Erlenmeyer flask size. During the vigorous stirring, the reaction solution
27
was slowly added 4,4'dimethyl2,2'bipyridine (0.40 g, 2.17 mmol) and stirred for 30 min
(color changed from red to green). The reaction mixture was poured into ice water
(200 ml) and kept at 5oC for 1 h. The yellow precipitate was filtered, washed with
ice water (30 ml x 3) and dissolved with 10% NaOH. The initial pH was adjusted
to 2 by 10% HCl and filtered again. YN-13 was obtained as a white solid (0.22 g, 12 %);
m.p.> 260 oC;
1H NMR (300 MHz, DMSO-D6) δ 8.90 (d, J = 5.0 Hz, 2H), 8.82 (s, 2H),
7.90 (dd, J = 4.9, 1.5 Hz, 2H); 13
C NMR (75 MHz, DMSO-D6) δ 166.4, 156.0, 151.1, 140.0,
123.9, 120.0; ATR-FTIR (neat) 3112, 2437, 1706, 1603, 1458, 1285 and 1012 cm-1;
MS (ESI) m/z calcd for C12H8N2O4 (M-2H+) 243.0406, found 243.0450.
The mixture of YN-13 (0.22 g, 0.88 mmol), 1 ml of conc.sulfuric acid
and 20 ml of methanol were refluxed for 24 h. The reaction mixture was cooled to
room temperature. Then the neutral solution was adjusted with sodium hydroxide and
extracted with dichloromethane (30 ml x 3). The organic layer was dried with
anhydrous sodium sulfate. The crude reaction was evaporated to dryness obtained as
a solid (0.23 g, 94 %); m.p. 192 - 194 ºC; 1H NMR (300 MHz, CDCl3) δ 8.97 (s, 2H),
8.87 (d, J = 4.9 Hz, 2H), 7.91 (d, J = 4.9 Hz, 2H), 4.01 (s, 6H); 13
C NMR (75 MHz, CDCl3 )
δ 165.6, 156.5, 150.1, 138.6, 120.5, 52.7; ATR-FTIR (neat) 3000, 2920, 1727, 1589,
1433, 1290 and 1123 cm-1
; MS (ESI) m/z calcd for C14H12N2O4 (M+Na+) 295.0695,
found 295.0646.
3.3.1.3 The synthesis of N3,N
3´-dibutyl-[2,2´-bipyridine]-
3,3´-dicarboxamide (L3)
The mixture of 1 equiv. of A4 (1.00 g, 4.09 mmol) in dried toluene
was put in the round bottom flask, equipped with magnetic stirrer, nitrogen system
with a septum. Then, 3 equiv. of oxalyl chloride (1.75 ml, 20.0 mmol) were added
dropwise at room temperature. The mixture stirring was continued at room temperature
for overnight. Afterwards, the crude reaction was evaporated to dryness.
28
At 0 oC, dried THF (15 ml) was introduced to a stirred solution of
crude product. Then dried pyridine (1 equiv.) and dried n-butylamine (3 equiv.) were
added a suspension solution and left for 7 h at room temperature. And then water was
added. An aqueous solution of HCl was added (pH 5-7) and the mixture was stirred for
additional 10 min. The reaction mixture was extracted three times with DCM,
combined organic layers were washed with brine and dried over Na2SO4.
The organic solvent was removed in evaporator, to give crude product which was
purified by column chromatography on silica gel using 3% MeOH:DCM to get
the product L3 as brown-red solid (0.11 g, 8 %); 1H NMR (300 MHz, CD3OD)
δ 8.62 (dd, J = 4.9, 1.6 Hz, 2H), 8.05 (m, 2H), 7.56 (m, 2H), 4.90 (s, 2H),
3.20 (t, J = 6.8 Hz, 4H), 1.43 - 1.27 (m, 4H), 1.19 (ddd, J = 13.6, 8.7, 5.9 Hz, 4H), 0.88
(m, 6H); 13
C NMR (75 MHz, CD3OD) δ 168.8, 155.4, 149.2, 136.1, 132.5 - 132.2, 123.3,
39.0, 30.7, 19.6 - 19.3, 12.7; ATR-FIR (neat) 3252, 3069, 2957, 1631, 1579, 1411 and
1316 cm-1
; MS (ESI) m/z calcd for C22H28N2O2 (M+Na+) 377.1953, found 377.1687.
3.3.2 Synthesis dimeric iridium complex
The synthesis procedures of dimeric iridium complexes were reported
elsewhere [11]. In general synthesis is IrCl3.3H2O was combined with C^N ligand
for example; 2-phenylpyridine, dissolved in a mixture of 2-ethoxyethanol and DI water
before refluxing for 24 h. The solution was cooled to room temperature, and
the yellow precipitate was collected on a glass filter frit. The precipitate was washed
with ethanol and acetone to give a yellow solid of KM05
3.3.2.1 Tetrakis-(2-phenylpyridine-C2´,N)-(µ-dichloro) diiridium (KM05)
KM05 was obtained in 45 %; 1H NMR (300 MHz, acetone-D6)
δ 8.90 (d, J = 8.2 Hz, 2H), 8.51 - 8.32 (m, 4H), 8.23 (d, J = 8.1 Hz, 2H),
8.07 (dd, J = 8.2, 5.0 Hz, 2H), 7.96 - 7.82 (m, 4H), 7.67 (d, J = 5.5 Hz, 2H),
29
7.07 (t, J = 7.5 Hz, 2H), 7.01 - 6.89 (m, 4H), 6.45 (d, J = 7.4 Hz, 2H); 13
C NMR
(75 MHz, CDCl3) δ 155.5, 148.5, 146.9, 146.4, 137.4, 134.8, 127.0, 126.8, 124.9,
120.1, 118.6; ATR-FTIR (neat) 3039, 1603, 1476 and 1158 cm-1
; MS (ESI) m/z calcd
for C44H32Cl2Ir2N4 (M+) 1072.1263, found 1072.1036.
3.3.2.2 Tetrakis-(2-(thiophen-2´-yl)-pyridine-C5´,N)-(µ-dichloro)diiridium
(KM06)
KM06 was obtained in 35 %; 1H NMR (300 MHz, CDCl3)
δ 9.01 (d, J = 4.8 Hz, 1H), 7.62 (t, J = 7.5 Hz, 1H), 7.51 (d, J = 8.4 Hz, 1H),
7.09 - 7.03 (m, 1H), 6.62 (t, J = 6.4 Hz, 1H), 5.97 - 5.88 (m, 1H); 13
C NMR (75 MHz,
CDCl3) δ 165.0, 151.6, 149.9, 145.7, 136.7, 129.3, 127.6, 118.9, 117.0 ; ATR-FTIR
(neat) 3057, 1601, 1470 and 1152 cm-1
; MS (ESI) m/z calcd for C36H24Cl2Ir2N4S4 (M+)
1095.9519, found 1095.9364.
3.3.2.3 Tetrakis-(2-(2´,4´-difluorophenyl)-pyridine-C6´,N)-(µ-dichloro)
diiridium (KM07)
KM07 was obtained in 38 %; 1H NMR (300 MHz, CDCl3) δ 9.12
(d, J = 5.2 Hz, 1H), 8.31 (d, J = 8.4 Hz, 1H), 7.83 (t, J = 7.6 Hz, 1H), 6.83 (t, J = 6.2
Hz, 1H), 6.41 - 6.25 (m, 1H), 5.29 (dd, J = 9.1, 2.2 Hz, 1H); 13
C NMR (75 MHz,
CDCl3) δ165.3, 165.2, 164.2, 164.0, 162.2, 162.0, 160.8, 160.6, 158.7, 158.6, 151.3,
147.6, 147.5, 137.5, 127.8, 127.8, 127.7, 122.9, 122.5, 112.8, 112.7, 112.6, 112.5,
30
98.5, 98.1, 97.8; ATR-FTIR (neat) 3086, 1599, 1477, 1294, 1162 and 1112 cm-1
;
MS (ESI) m/z calcd for C44H24Cl2F8Ir2N4 (M+) 1231.0744, found 1239.0241.
3.3.2.4 Tetrakis-(1-(2´,4´-difluoro-phenyl)-1H-pyrazole-C6´,N
2)-
(µ-dichlo-ro) diiridium (KM08)
KM08 was obtained in 55 %; 1H NMR (300 MHz, CDCl3)
δ 8.43 (br, 1H), 7.75 (br, 1H), 7.23 (br, 2H), 6.68 (br, 1H), 6.57 - 6.31 (br, 1H), 5.36 (s, 1H);
ATR-FTIR (neat) 3086, 1613, 1480, 1257, 1107 and 1031 cm-1
; MS (ESI) : m/z calcd
for C37H23Cl2F8Ir2N8 (M+) 1190.0062, found 1195.0020.
3.3.3 Synthesis charged iridium(III) complex
3.3.3.1 [(dimethyl 2,2´-bipyridine-3,3´-dicarboxylate)-bis-(2-(phenyl)
pyridine-C2´,N)-iridium(III)] hexafluorophosphate (NU02)
KM05 (0.10 g, 0.10 mmol) and L1 (0.06 g, 0.22 mmol) was dissolved
in solution mixture of MeOH (10 ml) and DCM (10 ml). The reaction mixture was stirred
and refluxed at 45˚C under nitrogen for 24 h. After that, the red-orange solution was
cooled to room temperature then an excess of KPF6 (0.4 g, 2.17 mmol) was added.
The suspension was stirred for 1 h. then filtered by using sintered glass funnel.
The filtrate was removed organic solvent, and then crude product was purified by
column chromatography on silica gel using 5% MeOH:DCM to get the target product
31
as a red-orange solid (0.24 g, 93 %);1H NMR (300 MHz, CDCl3) δ 8.40 (s, 2H),
8.17 (s, 4H), 7.79 (d, J = 7.5 Hz, 2H), 7.67 (t, J = 7.7 Hz, 2H), 7.50 (d, J = 7.5 Hz, 2H),
7.49 (s, 2H), 7.08 (m, 4H), 6.96 (t, J = 7.3 Hz, 2H), 6.24 (d, J = 7.3 Hz, 2H), 3.87 (s, 6H);
13C NMR (75 MHz, CDCl3) δ 165.0, 155.9, 151.6, 149.1, 143.3, 139.4, 138.5, 133.1,
131.8, 131.0, 127.8, 124.8, 123.7, 123.0, 119.6, 113.9, 53.6; ATR-FTIR (neat) 3085,
2923, 1731, 1600, 1412, 1305 and 1296 cm-1
; MS (ESI) m/z calcd for C36H28IrN4O4
(M+-PF6)773.1740, found 773.1668.
3.3.3.2 [(dimethyl2,2´-bipyridine-4,4´-dicarboxylate)-bis-(2-(phenyl)
pyridine-C2´,N)-iridium(III)] hexafluorophosphate (KM09)
The synthesis procedure of KM09 is similar to NU02. KM05
(0.10 g, 0.11 mmol), L2 (0.06 g, 0.22 mmol) and KPF6 (0.4 g, 2.17 mmol) was used
in the reaction. After purification column chromatography on silica gel using 5%
MeOH:DCM. The KM09 was achieved (0.13 g, 64 %) as a red-orange solid; 1H NMR
(300 MHz, CDCl3) δ 9.06 (s, 2H), 8.12 (d, J = 5.5 Hz, 2H), 7.98 (d, J = 5.3 Hz, 2H),
7.90 (d, J = 8.1 Hz, 2H), 7.76 (t, J = 7.8 Hz, 2H), 7.69 (d, J = 7.6 Hz, 2H),
7.57 (d, J = 5.6 Hz, 2H), 7.07 (dd, J = 13.4, 6.7 Hz, 4H), 6.94 (t, J = 7.3 Hz, 2H),
6.28 (d, J = 7.4 Hz, 2H), 4.05 (s, 6H); ATR-FTIR (neat) 3043, 2921, 1729, 1607,
1478, 1261 and 1122 cm-1
; MS (ESI) m/z calcd for C36H28IrN4O4 (M+-PF6) 773.1740,
found 773.1644.
3.3.3.3 [(N3,N
3´-dibutyl-[2,2´-bipyridine]-3,3´-dicarboxamide)-bis-
(2-(phenylpyridine-C2’,N)-iridium(III)] hexafluorophosphate (KM10)
32
The synthesis procedure of KM10 is similar to NU02. KM05
(0.17 g, 0.16 mmol), L3 (0.11 g, 0.32 mmol) and KPF6 (0.4 g, 2.17 mmol) was used in
the reaction. The product was purified by column chromatography by using
5% MeOH:DCM to give red-orange solid of KM10 (0.27 g, 86 %); 1H NMR
(300 MHz, CDCl3) δ 8.09 (d, J = 7.8 Hz, 1H), 7.98 (d, J = 5.3 Hz, 1H),
7.86 (d, J = 7.9 Hz, 1H), 7.72 (dd, J = 15.9, 7.9 Hz, 1H), 7.64 (d, J = 7.8 Hz, 1H),
7.37 - 7.25 (m, 1H), 7.06 (dd, J = 12.1, 5.0 Hz, 1H), 7.00 (t, J= 7.5 Hz, 1H),
6.94 - 6.75 (m, 2H), 6.23 (d, J = 7.5 Hz, 1H), 3.34 (dd, J = 13.3, 6.6 Hz, 2H),
1.58 (dt, J = 15.0, 6.6 Hz, 2H), 1.46 - 1.19 (m, 5H), 0.89 (dd, J = 15.6, 8.2 Hz, 4H);
13C NMR (75 MHz, CDCl3) δ 166.8, 164.9, 154.8, 150.4, 149.6, 147.8, 143.4, 138.1,
137.8, 131.8, 130.7, 127.2, 124.6, 123.5, 122.7, 119.4, 40.5, 31.0, 29.6, 20.1, 13.0;
ATR-FTIR (neat) 3428, 3063, 2923, 1661, 1607, 1529, 1478 and 1312 cm-1
;
MS (ESI) m/z calcd for C42H42IrN6O2 (M+-PF6) 855.2998, found 855.2889.
3.3.3.4 [(4,5-diaza-9,9´-spirobifluorene-N-N´)-bis-(2-phenylpyridine
C2´,N) iridium(III)] hexafluorophosphate (KM01)
The synthesis procedures of K1 were reported elsewhere [4] and
used in our work. K1 (0.20 g, 0.23 mmol) and KPF6 (0.4 g, 2.17 mmol) were dissolved
in solution mixture of MeOH (10 ml) and DCM (10 ml). The product was purified by
column chromatography on silica gel using 3% MeOH:DCM to get the target product
33
as a yellow solid (0.19 g, 87 %); 1H NMR (300 MHz, CDCl3): δ 7.95 (t, J = 6.5 Hz, 4H),
7.86 (t, J = 7.8 Hz, 4H), 7.79 - 7.64 (m, 4H), 7.46 (t, J = 7.5 Hz, 2H), 7.35 (d, J = 10.1 Hz, 4H),
7.32 - 7.19 (m, 4H), 7.04 (t, J = 7.4 Hz, 2H), 6.94 (t, J = 7.3 Hz, 2H), 6.70 (d, J = 7.5 Hz, 2H),
6.45 (d, J = 7.5 Hz, 2H);13
C NMR (75 MHz, ) δ 166.8, 161.8, 158.8, 149.4, 148.6,
144.2, 143.9, 143.7, 141.9, 141.5, 138.5, 134.6, 132.0, 130.6, 129.6, 128.8, 128.2,
124.4, 123.8, 123.8, 122.9, 120.8, 119.5; ATR-FTIR (neat) 3037, 1607, 1478 and
1163 cm-1
; MS (ESI) m/z calcd for C45H30IrN4 (M+-PF6) 819.2100, found 819.2100.
3.3.3.5 [(4,5-diaza-9,9´-spirobifluorene-N-N´)-bis-(2-thiophen-
2´-yl-pyridineC5´,N)-iridium(III)] hexafluorophosphate (KM02)
The synthesis procedures of K2 were reported elsewhere [4] and
used in our work. K2 (0.19 g, 0.23 mmol) and KPF6 (0.4 g, 2.17 mmol) were used
in the reaction. The product was purified by column chromatography on silica gel
using 3% MeOH:DCM to get the target product as orange solid (0.16 g, 73 %);
1H NMR (300 MHz, CDCl3) δ 7.95 (dd, J = 13.9, 6.6 Hz, 2H), 7.85 (dd, J = 8.8, 6.7 Hz, 2H),
7.58 (m, 2H), 7.52 - 7.35 (m, 8H), 7.22 (m, 2H), 7.10 (dd, J = 15.0, 8.3 Hz, 2H),
6.67 (dd, J = 16.7, 7.8 Hz, 2H), 6.41 (d, J = 4.7 Hz, 2H); 13
C NMR (75 MHz, CDCl3)
δ 164.2, 161.9, 149.8, 149.0, 145.8, 143.6, 141.9, 141.3, 138.9, 136.9, 134.7, 130.6,
129.8, 129.6, 128.8, 128.3, 123.9, 121.0, 120.9, 120.9, 118.3; ATR-FTIR (neat) 2950,
1604, 1473 and 1157 cm-1
; MS (ESI) m/z calcd for C41H26IrN4S2 (M+-PF6) 831.1228,
found 831.1243.
3.3.3.6 [(4,5-diaza-9,9´-spirobifluorene -N-N´)-bis-(2-(2´,4´-difluorophenyl)
pyridine C6´,N)-iridium(III)] hexafluorophosphate (KM03)
34
The synthesis procedures of K3 were reported elsewhere [4] and
used in our work. K3 (0.21 g, 0.23 mmol) and KPF6 (0.4 g, 2.17 mmol) were used
in the reaction. The product was purified by column chromatography on silica gel
using 3% MeOH:DCM to get the target product as yellow solid (0.16 g, 89 %);
1H NMR (300 MHz, CDCl3) δ 8.35 (d, J = 8.6 Hz, 1H), 7.98 - 7.82 (m, 3H),
7.78 (dd, J = 4.2, 1.5 Hz, 1H), 7.52 - 7.29 (m, 4H), 7.23 (dd, J = 13.9, 6.3 Hz, 1H),
6.70 (d, J = 7.6 Hz, 1H), 6.65 - 6.47 (m, 1H), 5.82 (dd, J = 8.3, 2.0 Hz, 1H);
ATR-FTIR (neat) 3087, 1602, 1478, 1248, 1165 and 1105 cm-1
; MS (ESI) m/z calcd
for C45H26F4IrN4 (M+-PF6) 891.1723, found 891.1766
3.3.3.7 [(4,5-diaza-9,9´-spirobifluorene -N-N´)-bis-(1(2´,4´difluorophenyl) -
1H-pyrazole-C6,N
2)-iridium(III)] hexafluorophosphate (KM04)
The synthesis procedure of KM04 is similar to NU02. KM08
(0.10 g, 0.13 mmol), 4,5-diaza-9,9'-spirobifluorene (0.06 g, 0.19 mmol) and KPF6
(0.4 g, 2.17 mmol) were used in the reaction. The product was purified by
column chromatography on silica gel using 3% MeOH:DCM to get the target product
as a white solid (0.11 g, 85 %); 1H NMR (300 MHz, CDCl3) δ 8.42 (d, J = 2.6 Hz, 1H),
7.97 - 7.80 (m, 2H), 7.57 - 7.33 (m, 4H), 7.32 - 7.17 (m, 1 H), 6.83 - 6.63 (m, 3H),
35
5.86 (d, J = 7.6 Hz, 1H); ATR-FTIR (neat) 3166, 1615, 1416, 1258, 1108 and 1037 cm-1
;
MS (ESI) m/z calcd for C41H24F4IrN6 (M+-PF6) 869.1628, found 869.1676.
3.4 OLEDs device fabrication
The iridium complexes were prepared as previously described. A thin film of
electroluminescent material was sandwiched between two electrodes to fabricate
the devices. The devices were fabricated by solution processing, which is easily done
by spin-coating the solution on indium tin oxide (ITO) coated glass-substrates.
3.4.1 Cleaning process for the patterned ITO glass
The ITO glass was cleaned sequentially with a detergent in ultrasonic bath
at 40ºC for 10 min, deionized (DI) water for 5 min (two times), acetone for 5 min
(two times), 2-propanol for 5 min (two times) and hot vapor of ethanol at 225 ºC
for 10 min. Finally, the substrate was dried in vacuum oven at 100 ºC for 10 min and
led to UV ozone cleanser for 5 min. The cleaning step can be summarized in Figure 3.2.
Figure 3.2 Cleaning process for the patterned ITO glass
10 min
10 min
sonicated 5 min/ 2 times
sonicated 10 min
Deionized water
Acetone
sonicated 5 min/ 2 times
2-Propanol
Hot vapor ethanol
Dried in vacuum oven at 100 ºC
Cleaned in UV ozone cleaner
Cleaned ITO glass
sonicated 5 min/ 2 times
Detergent
36
3.4.2 Fabrication of OLEDs devices
After the ITO glasses were cleaned, the fabrication for OLEDs devices
as followed;
3.4.2.1 The coating PEDOT:PSS
First step, the ITO glass was covered by adhesive tape with four edges.
The top surface was blow out the dust by N2 gas. Second step, the PEDOT:PSS
(450 µl) was dropped onto a ITO glass placed on spin-coater and then spun
at 3000 rpm for 180 s. Finally, PEDOT:PSS film was baked at 260 ºC for 10 min and
keep in desiccators.
3.4.2.2 Spin coating emitting layer
In this thesis, we studied in two systems in the OLEDs which are
emitter in pure acetronitrile solvent and co-solvent as acetronitrile and
1,2-dichlorobenzene. Spin coating method for iridium (III) complexes (OLEDs),
KM01-KM04. The mixture of KM01-KM04 and BMIMP in acetonitrile 1:1 ratio
were filtered through PVDF membrane syringe (0.45 µm pore size), and then
the filtered solutions (350 µl) were spin-coated onto a patterned ITO glass coated with
the PEDOT:PSS film at 2500 rpm, 180 s. Then the ITO glass coated with the iridium (III)
complexes films were dried in vacuum oven at 60 °C for 30 min. In addition,
we studied to co-solvent as acetonitrile and 1,2-dichlorobenzene in similar procedure.
3.4.2.3 Electron transporting of organic deposition
The organic material in this work is TPBi was deposited after
the spin-coated. The assembly was transferred into a deposition chamber of
the thermal evaporator with a base pressure of 10-6
mbar for the deposition of
an organic material. The organic material was deposited on top of glass substrate by
evaporation at current of 10 A with evaporation rate of 1-3 Å/s.
3.4.2.4 Cathode electrode deposition
Finally, a thin LiF layer and Al cathode were sequentially
co-evaporated through a shadow mask with 5 mm wide slits arranged perpendicularly
to the 5 mm2fingers ITO, to obtain OLED with an active area. The operating vacuum
for evaporation of this cathode was under 10-6
mbar at high evaporation rate of
5-10 Å/s. The thickness of LiF and Al were 0.5 and 100 nm, respectively.
37
In order to investigate the performance of devices, standardize of
the measurement which the Luminance, current efficiency (cd/A), power efficiency
(lm/W), current density (mA/cm2) and CIE coordinate were performed with a I-L-V
Testing kiethley.
3.5 Colorimetric sensor study
The study of 2x10-2
M charge iridium(III) complexes (NU02 and KM09) in dried
acetonitrile for amine sensor were investigated by visible absorption in the range
of 400 - 800 nm. The reaction mixture was combined in beaker size 5 ml. Then,
the solution was stirred and heated at 60 ºC and measured the visible absorption
at 0 min, 5 min, 30 min, 60 min and 120 min. The number equivalents of acid were
varied including without HCl, 1 equiv. (0.1 M), 10 equiv. (1 M) and 100 equiv. (10 M)
of HCl. For study the equivalents of n-Butylamine, we studied with 1 equiv. (0.015 M)
and 3 equiv. (0.15 M) acid in dried acetonitrile.
38
CHAPTER 4
RESULTS AND DISSCUSSIONS
4.1 Synthesis of N^N ligand
4.1.1 The synthesis of dimethyl-2,2´-bipyridine-3,3´-dicarboxylate (L1)
The A4 was synthesized by reaction of the oxidation reaction
of 1,10-phenanthroline with potassium hydroxide and potassium permanganate to get
the resulting product as a white solid, 97% yield. The A4 was characterized by FT-IR
(appendix A) and NMR techniques, shown in Figure 4.1.
Figure 4.1 Synthetic method of A4
The mechanism of the oxidation reaction of 1,10-Phenanthroline shows in
Figure 4.2. The dimethyl on bipyridine derivative was converted into carboxylic acid
group, it was converted to A4 as white solid by KMnO4 and KOH.
Figure 4.2 The mechanism of oxidation reaction
A4 is a symmetric molecule as only 3 signals without carboxylic acid
proton. The 1H NMR spectrum of A4 in DMSO-D6 shows the signal at chemical shift
at δ 8.73 (2H), 8.35 (2H) and 7.67 - 7.54 (2H) assigned as proton of pyridine ring.
39
Figure 4.3 1H NMR in DMSO-D6 of A4
After that L1 was synthesized by reaction of the esterification reaction
of A4 with methanol and conc. sulfuric acid to get the resulting product as colorless
solid, 45% yield.
Figure 4.4 Synthetic method of L1 precursor
The mechanism of esterification reaction of L1 can be explained in Figure 4.5.
Figure 4.5 The mechanism of esterification reaction
40
The dicarboxylic acid on bipyridine derivative was converted into ester
group by the lone pair of oxygen in dicarboxylic acid was protonated with H2SO4
to give the carbocation. Then MeOH which nucleophillic attacks alcohol group on
bipyridine derivative and the elimination of H2O and H+ provided the target compound
as a white solid. The product was characterized by NMR in Figure 4.6 and FT-IR
(appendix A.1).
L1 is a symmetric molecule as only 4 signals of molecule was observed.
The 1H NMR spectrum of L1 shows the signal at δ 8.79 (2H), 8.40 (2H) and
7.54 - 7.40 (2H) ppm assigned as proton of pyridine ring. The chemical shift at 3.70
(6H) was assigned as the protons of the methyl group.
Figure 4.6 1H NMR in CDCl3 of the L1
4.1.2 The synthesis of dimethyl-2,2´bipyridine-4,4´dicarboxylate (L2)
The dimethyl-2,2'bipyridine-4,4'dicarboxylate (L2) ligand was synthesized
in two steps as shown in Figure 4.7. The intermediate (YN-13) was prepared oxidation
reaction by H2SO4/Na2Cr2O7 in 12% yield. Then, esterification reaction by methanol
and conc. sulfuric acid was used to get the target product (L2) in 94% yield.
Figure 4.7 The synthetic route of dimethyl-2,2´bipyridine-4,4´dicarboxylate (L2)
41
YN-13 ligand was synthesized by oxidation reaction of dimethyl on
bipyridine. It was oxidized by sodium dichromate (Na2Cr2O7) in acidic condition
to give aldehyde. Then, the resulting intermediate was further oxidized to carboxylic acid
to obtained as a white solid in 60% yield. The mechanism of the oxidation reaction
can be explained in Figure 4.8.
Figure 4.8 The mechanism of oxidation reaction
The characterization of YN-13 was investigated by 1H NMR,
FTIR and MS
(appendix A.3). The YN-13 is a symmetrical structure. The 1H NMR spectra shows
only 3 signals resonance chemical shift at 8.90 (2H), 8.82 (2H), and 7.90 (2H) ppm
assigned at as protons of aromatic pyridine ring as shown in Figure 4.9. The 13
C NMR
spectrum of YN-13 shows 5 carbon resonances for aromatic pyridine carbon and one
signal for carboxylic group (appendix A.3).
Figure 4.9 1H NMR in DMSO-D6 of YN-13
42
Then, the esterification of YN-13 with methanol and sulfuric acid was used
to synthesize the L2 ligand. The characterization of L2 was investigated by the
1H NMR,
FTIR and MS (appendix A.4).
The L2 is a symmetrical structure. The 1H NMR spectra only 4 signals
chemical shift at 8.97 ppm (2H), 8.87 (2H), and 7.91 (2H) assigned as protons
of aromatic pyridine ring and 4.01 ppm (6H) assigning as protons of ester functional
group as shown in Figure 4.10. The 13
C NMR spectra of L2 show 5 signals
for aromatic pyridine carbon and 1 signal for ester group (appendix A.4).
Figure 4.10 1
H NMR in CDCl3 of L2
4.1.3 The synthesis of N3,N
3´-dibutyl-[2,2´-bipyridine]-3,3´-dicarboxamide (L3)
L3 ligand was synthesized in two steps in Figure 4.11. A4 react with oxalyl
chloride to get the crude product. Then the amide group was formed by n-butylamine
to get the target product L3 in 8% yield.
Figure 4.11 The synthetic route to N3,N
3´-dibutyl-[2,2´-bipyridine]-3,3´-
dicarboxamide (L3)
The mechanism reaction shows in Figure 4.12. The dicarboxylic acid
on bipyridine derivative was converted to acid chloride, then it was converted
43
to N3,N
3´-dibutyl-[2,2´-bipyridine]-3,3´-dicarboxamide (L3) as orange solid by
pyridine, THF and n-butylamine.
Figure 4.12 The mechanism of oxalyl chloride reaction
The characterization of L3 was investigated by the 1H NMR,
FTIR and MS
as shown in Figure 4.13.
4000 3500 3000 2500 2000 1500 1000 50030
40
50
60
70
80
90
100
110
% Tra
nsmitta
nce
Wavenumber (cm-1)
Figure 4.13 1H NMR in CD3OD and FTIR of N
3,N
3´-dibutyl-[2,2´-bipyridine]-
3,3´-dicarboxamide (L3)
44
The L3 is a symmetrical structure. The 1H NMR spectra shows 8 signals
chemical shift at 8.62 (2H), 8.05(2H), and 7.56(2H) ppm assigned as protons
of aromatic pyridine ring, δ 4.90 (2H) assigned as protons amide, 3.20 (4H),
1.43 - 1.27 (4H), 1.19 (4H) and 0.88 (6H) ppm assigned as protons of butyl group
in amide group. The 13
C NMR spectra of L3 show 5 signals for aromatic pyridine
carbon and 5 signals for amide group (appendix A.5).
4.2 The charged iridium(III) complex
Generally, the first step is the synthesis of dinuclear cyclometalatediridium(III)
chlorobridged by the refluxing with C^N ligand and iridium(III) chloride hydrate
in 2-ethoxyethanol for 24 h. is shown below.
The second step is the synthesis of charged iridium(III) complexes by refluxing
with N^N bidentate ligand and KPF6 in MeOH and DCM for 24 h. KM01-KM03 were
synthesis in some second step as KPF6. Whereas KM04 synthesis in all second step.
4.2.1 The charged iridium(III) complexes for OLEDs
The charged iridium(III) complexes were successfully formed as showed
in Figure 4.14.
4.2.1.1 Synthesis iridium(III) complexes and characterization
45
Figure 4.14 Synthetic routines of the charged iridium(III) complexes for OLEDs
KM01 is a symmetric molecule as only 15 proton signals of one ppy
and spiro ligands were observed at chemical shift 7.95 - 6.45 ppm as shown in Figure 4.15.
The signals at chemical shift 7.95 (4H), 7.86 (4H), 7.79 - 7.64 (4H) and 7.46 (2H) ppm
were assigned to fourteen protons of the spiro ligand. The signal chemical shift
at 7.35 (4H), 7.32 - 7.19 (4H), 7.04 (2H), 6.94 (2H), 6.70 (2H) and 6.45 (2H) ppm
were assigned to protons of phenyl pyridine ring ligand. Mass spectrum of the complex
at 819.2100 (m/z) was assigned to M+-PF6 (appendix A.13).
46
Figure 4.15 1H NMR spectrum in CDCl3 solution of KM01
KM02 is a symmetric molecule as only 13 proton signals
of thiophenyl pyridine and spiro ligands were observed at chemical shift 7.85 - 6.41 (26H)
ppm as shown in Figure 4.16.
Figure 4.16 1
H NMR spectrum in CDCl3solution of KM02
It was found that the signals at chemical shift 7.95 (2H), 7.85 (2H),
7.72 (4H), 7.58 (2H), 7.52 - 7.35 (8H), 7.22 (2H), 7.10 (2H), 6.67 (2H) and 6.41 (2H) ppm
assigned to 26 aromatic protons of pyridine and spiro ligands. Mass spectrum
of the complex at 831.1243 (m/z) is assigned to M+-PF6 (appendix A.14).
Similarly, KM03 also is a symmetric molecule as only 13 proton
signals of difluorophenyl pyridine and spiro ligands. Mass spectrum of the complex
showed the peaks at 891.1766 (m/z) is assigned to M+-PF6 (appendix A.15).
47
KM04 shows a symmetric molecule of difluorophenyl pyrazole
and spiro ligands at chemical shift 8.35-5.82 ppm. Mass spectrum of the complex
at 869.1676 (m/z) is assigned to M+-PF6 (appendix A.16).
4.2.1.2 The photophysical properties
The UV-Vis absorption spectra of KM01-KM04 in dichloromethane
solutions at room temperature are shown in Figure 4.17 (a). The complexes exhibit
main absorption bands below 300 nm region, due to spin-allowed * transition
in ligand-centered (LC) transition of the C^N cyclometalated ligand and N^N ligand.
The weak absorption bands shows at 330 - 450 nm corresponding to metal-to-ligand
charge transfer (MLCT) transition, respectively.
250 300 350 400 450 500 550 600
0.0
0.2
0.4
0.6
0.8
1.0
KM01
KM02
KM03
KM04
No
rm
ali
zed
Ab
sorp
ba
nce I
nte
nsi
ty (
a.u
.)
Wavelength (nm)
450 500 550 600 650 700
0.0
0.2
0.4
0.6
0.8
1.0 KM01
KM02
KM03
KM04
No
rm
ali
zed
PL
In
ten
sity
(a
.u.)
Wavelength (nm)
Figure 4.17 (a) UVVis absorption spectra (b) Emission spectra of 1x10-5
M
KM01-KM04 in dichloromethane solution at room temperature
The emission spectra of KM01-KM04 in dichloromethane solutions
at room temperature are shown in Figure 4.17 (b). The maximum emission
wavelengths of KM01-KM04 are 550, 586, 505 and 488 nm, respectively.
(b)
(a)
48
These complexes generated color as yellow, orange, green and blue. From the results,
the maximum emission wavelength of KM02 shows red-shifted compared KM01
because of electron donating groups (thiophenyl pyridine). In the another hand,
KM03 and KM04 show blue-shifted compared KM01 because of electron
withdrawing groups (fluorine atoms). The emission quantum yield about 0.01 - 0.07
was obtained by using a solution of quinine sulfate served as the standard under
air condition. The emission spectra of a cationic cyclometalated iridium(III)
complexes in solution were successfully tuned from green to red. The photophysical
characteristics of these complexes are summarized in Table 4.1.
Table 4.1 Photophysical characteristics of KM01-KM04 solution
Complex
Solution
abs a
(nm, log )
ex
(nm)
em
(nm) PL
b
KM01
KM02
KM03
KM04
269 (4.7), 305 (4.3), 418 (3.7)
274 (4.7) 319 (4.4), 424 (3.9)
264 (4.7), 316 (4.3), 429 (3.1)
256 (4.7), 319 (4.1), 416 (3.4)
305
319
316
319
550
586
505
488
0.014
0.003
0.054
0.078
a in dichloromethane solution (2x10
-5 M)
b Determined in dichloromethane solutions (A < 0.1) at room temperature using quinine
sulfate solution in 0.01 M H2SO4 as a standard under air condition
Figure 4.18 The picture of KM01-KM04 in dichloromethane solutions at room
temperature under normal light (left) and 356 nm UV light (right)
49
4.2.1.3 Electrochemical properties
The electrochemical properties of KM01-KM04 were investigated
by cyclic voltammetry (Figure 4.19) and the redox potentials are summarized
in Table 4.2. The cyclic voltammogram was studied with Ir(III) complexes
in a 1x10-3
M (dry CH3CN) containing 0.1 M tetrabutylammoniumhexafluorophosphate
(TBAPF6) and working electrode with a glassy carbon (GC). Ferrocene was used
as the standard for a monoelectronic chemically and electrochemically reversible
reaction.
Figure 4.19 Cyclic voltammograms of 1x10-3
M KM01-KM04 in dry CH3CN with
scan rate of 100 mV/s and 0.1 M TBAPF6 as electrolyte
In addition, the HOMO and LUMO energy levels of those iridium
complexes were estimated according to the electrochemical and photophysical
absorption. The energy gap (Eg) were estimated according to onset of absorption
spectra (Eg = 1240/onset). The HOMO and LUMO energy levels were calculated from
equation; HOMO = -e(Eox + 4.8 eV - Eox(ferocene)) and LUMO = HOMO + Eg [45].
The electrochemical properties of KM01-KM04 are summarized in Table 4.2.
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
-80
-60
-40
-20
0
20
40
KM01
KM02
KM03
KM04
Ferrocene
Cu
rren
t (m
A)
Potential (V)
50
Table 4.2 Electrochemical properties and energy levels of KM01-KM04
Complex Eoxa (V) onset
b Eg
c (eV) HOMO
d (eV) LUMO
e (eV)
KM01
KM02
KM03
KM04
1.33
1.23
1.66
1.72
491
510
451
419
2.53
2.43
2.75
2.96
-5.69
-5.59
-6.02
-6.08
-3.16
-3.16
-3.27
-3.12
a Measured in CH3CN solution containing 0.1 M n-Bu4NPF6 as a supporting
electrolyte at a scan rate of 100 mV/s
b Estimated from the absorption spectra
c Estimated from the onset of the absorption spectra (Eg = 1240/onset)
d Calculated from HOMO = - e(Eox + 4.8eV - Eox(ferocene)) where Eox(ferocene) = 0.44 V
e Calculated from equation LUMO = HOMO + Eg
As shown in Table 4.2, the oxidation potentials of KM01-KM04
were observed at 1.33, 1.23, 1.66 and 1.72 V, respectively, attributed to the oxidation
of Ir(III) to Ir(IV) [52]. Compared with KM03 and KM04, the energy gap of KM01
showed a high value which can be explained the electron withdrawing group on ligand
of KM03 and KM04. In another hand, KM02 showed a low energy gap at 2.43 eV
due to electron rich thiophenylpyridine ligand.
The results were supported by the DFT calculations. Specifically
of KM04, the HOMO is distributed between the Ir atom and the benzene rings of the
difluorophenylpyrazole ligand and LUMO are mainly located on the bipyridine rings
are shown in Figure 4.20.
Figure 4.20 HOMO and LUMO distribution of the KM04
HOMO LUMO
51
4.2.1.4 Electroluminescence study.
The electroluminescence of the KM01-KM04 was investigated
with a multi-layer OLED by using host-guest technique, in Figure 4.21
Figure 4.21 Structures of simple OLED devices.
The figure showed the configuration of the devices which
PEDOT:PSS was used as a hole-injecting layer. The KM01-KM04 were used as the
emitter with ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6)
with a pure acetonitrile to provide additional PF6- anions. 1,3,5-tris(N-phenyl-
benzimidizol-2-yl)benzene (TPBi), electron transporting layer, was placed between
cathode and emitting layer for reduce the energy barrier in the injection of electron
from cathode to emitting layer [46]. The J-V-L characteristics of multi-layer OLED
devices are shown in Figure 4.22.
Figure 4.22 Current density and brightness versus applied bias voltage of the
device structure ITO/PEDOT:PSS/KM01-KM04:BMIMPF6
(1:1)/TPBi/LiF/Al in acetronitrile
0 2 4 6 8 10 12
0
40
80
120
160
200
240 KM01
KM02
KM03
KM04
Voltage (V)
Cu
rren
t d
ensi
ty (m
A/c
m2
)
1
10
100
1000
Bri
gh
tnes
s (cd
/m2
)
52
The maximum brightness at 2027, 103, 879 and 27cd/m2 and
the maximum current efficiency at 1.72, 0.07, 1.68 and 0.19 cd/A can be observed
with KM01-KM04, respectively. We found that KM01 gave high brightness
to 2027 cd/m2 compared others. The KM01 show that a maximum current efficiency
at 1.72 cd/A, the brightness 2027 cd/m2 at 10 V and CIE coordinate (x,y) of 0.48, 0.50.
can be observed. The characteristics of multi-layer OLED devices of KM01-KM04
are summarized in Table 4.2.
Table 4.3 Summary of host-guest multi-layer OLED performances with configurations
of ITO/PEDOT:PSS/KM01-KM04:BMIMPF6 (1:1)/TPBi/LiF/Al
Complex Vturn-on
a
(V)
Bmaxb
(cd/m2)
CEmaxc
(cd/A)
PEmaxd
(lm/W)
CIEe
(x, y)
KM01
KM02
KM03
KM04
4.7
5.7
5.3
4.9
2027
130
879
27
1.72
0.07
1.68
0.19
0.77
0.27
0.70
0.10
0.48, 0.50
0.56, 0.42
0.29, 0.53
0.24, 0.43
aThe voltage at luminance of 1 cd/m
2
b Maximum brightness
c Current density at maximum luminance
d Power efficiency at maximum luminance
e CIE coordinates
The results showed that KM04 gave a low brightness and current
efficiency. The result can be explained by the energy profile (Figure 4.23).
The HOMO level of KM04 was observed at -6.08 eV which is not suitable with
HOMO level of PEDOT:PSS at -5.3 eV (Figure 4.23). Moreover, we found that
the KM04 gave a low solubity in pure acetronitrile. This observation could also be
a responsible for a low performance.
53
Figure 4.23 Schematics of energy level (eV) diagram of host-guest multi-layer
OLEDs using KM01-KM04 as emitter
The CIE coordinates and their emission color for OLED devices of
KM01-KM04 are shown in Figure 4.24.
Figure 4.24 CIE 1931 coordinates (x,y) and emission colour for OLED devices
of KM01-KM04 with configuration of ITO/PEDOT:PSS/Iridium
complexes:BMIMPF6/TPBi/LiF/Al
We found that, the charged complexes successfully generated
emission color from yellow, orange, green and blue with related the color under
UV light (Figure 4.18). This color is according to energy gap (Table 4.2). KM04 is
high energy band gap more other complexes as a result green. While KM02 is small
energy band gap when compared KM01, KM03 and KM04.
54
To improve a better performance, KM04 was studied with
a co-solvent as acetonitrile and 1,2 dichlorobenzene (1:1 v/v) and modified ratio of ionic
liquid to (1:0.75). The J-V-L characteristics are shown in Figure 4.26.
0 2 4 6 8 10 12
0
100
200
300
400
500
600
700
KM04
Voltage (V)
Cu
rren
t d
ensi
ty (m
A/c
m2
)
0.1
1
10
100
1000
Bri
gh
tnes
s (c
d/m
2)
Figure 4.25 Current density and brightness versus applied bias voltage of the
device structure ITO/PEDOT:PSS/KM04:BMIMPF6 (1:0.75)/
TPBi/LiF/Al
From the result, the better brightness at 212 cd/m2
and current
efficiency at 0.29 cd/A can be obtained which the modified system affected to smooth
film on ITO glass compared with pure acetronitrile. The performances are summarized
in Table 4.4.
Table 4.4 Summary of host-guest OLED device performances with configurations
of ITO/PEDOT:PSS/KM04:BMiMPF6(1:0.75)/TPBi/LiF/Al
Complex Vturn-on
a
(V)
Bmaxb
(cd/m2)
CEmaxc
(cd/A)
PEmaxd
(lm/W)
CIEe
(x, y)
KM04 5.1 212 0.29 0.13 0.22, 0.38
aThe voltage at luminance of 1 cd/m
2
b Maximum brightness
c Current density at maximum luminance
d Power efficiency at maximum luminance
e CIE coordinates
55
4.2.2 The charged iridium(III) complexes for chemical sensor application
The complexes were designed with active functional group (ester) in neutral
ligand as shown in structure of NU02 and KM09. The general synthesis was used
in two steps similar as OLEDs.
4.2.2.1 Synthesis iridium(III) complexes and characterization
Figure 4.26 Synthetic routines of the charged iridium(III) complexes for sensor
NU02 is a symmetric molecule as only 14 proton signals of one
ppy and bipyridine dicarboxylate ligands were observed at chemical shift 8.39 - 3.87
ppm as shown in Figure 4.32.
Figure 4.27 1H NMR spectrum in CDCl3 solution of NU02
56
The 1H NMR spectra of NU02 showed the signals at chemical shift
3.87 (6H) ppm assigned to six protons of the bipyridine dicarboxylateligand. The signals
at chemical shift 8.40 (2H), 8.17 (4H), 7.91 (2H), 7.79 (2H), 7.67 (2H), 7.50 (2H),
7.08 (4H), 6.96 (2H) and 6.24 (2H) ppm were assigned to 28 aromatic protons of pyridine
and ester ligands. Mass spectrum of the complex at 773.1668 (m/z) is assigned to M+-PF6
(appendix A.10).
KM09 is a symmetric molecule as only 14 proton signals of one ppy
and bipyridine dicarboxylate ligands were observed at chemical shift 9.06-4.05 ppm
(appendix A.11). The signal at chemical shift 4.05 (6H) ppm were assigned to six protons
of the bipyridine dicarboxylateligand. The signals at chemical shift 9.06 (2H), 8.12 (2H),
7.98 (2H), 7.90 (2H), 7.76 (2H), 7.69 (2H), 7.57 (2H), 7.07 (4H), 6.94 (2H) and
6.28 (2H) ppm were assigned to 28 aromatic protons of pyridine and ester ligands.
Mass spectrum of the complex showed the peaks at 773.1644 (m/z) assigned to M+-PF6
(appendix A.11).
4.2.2.2 The Photophysical properties
The UV-Vis absorption spectra of NU02 and KM09 in acetonitrile
solutions at room temperature are shown in Figure 4.28. The UV-visible absorption
spectra of the complex display a similar peak at reported in KM01-KM04 from LC and
MLCT transition, respectively. The absorbance of NU02 and KM09 found that covered
both UV-Visible range (240-500 nm). However, for the application in CCR technique,
we studied the changing colors in the visible range as shown in Figure 4.29 - 4.35.
250 300 350 400 450 500
0.0
0.2
0.4
0.6
0.8
1.0 NU02
KM09
No
rma
lize
d A
bso
rba
nce
In
ten
sity
(a
.u.)
Wavelength (nm)
Figure 4.28 UVVis absorption spectra of 2x10-5
M in CH3CN of the Ir(III)
complexes at room temperature
57
4.2.2.3 Study of iridium(III) complexes for colorimetric n-butylamine
sensor application in various conditions
Firstly, the chemical sensor was investigated by NU02 with
3 eq. n-BuNH2 in the three drop of conc. HCl condition (excess). This reaction was
monitored in Figure 4.30. Upon addition of reaction time, the absorption bands show
dramatically change to a blue shifted from 536 to 474 nm within 2 hour.
Condition 1: 1 eq. NU-02: 3 eq. n- BuNH2: conc HCl (excess)
450 500 550 600 650 700
0.0
0.2
0.4
0.6
0.8
1.0
No
rm
ali
zed
Ab
sorb
an
ce I
nte
nsi
ty (
a.u
.)
Wavelength (nm)
NU02
5 min
30 min
60 min
120 min
Figure 4.29 The Visible absorption spectra of NU02 [2.5x10-2
M] and n-BuNH2
in CH3CN solution with excess HCl at 5, 20, 60 and 120 min
Then, we studied the number equivalent of acid and n-BuNH2
in 4 conditions include without HCl as shown in Figure 4.30.
Condition 2: 1 eq. NU-02 [2.5x10-2 M: 1 eq. n- BuNH2 without HCl
500 550 600 650 700
0.0
0.2
0.4
0.6
0.8
1.0
0 min
5 min
30 min
60 min
120 min
Norm
ali
zed
Ab
sorb
an
ce I
nte
nsi
ty (
a.u
.)
Wavelength (nm)
Figure 4.30 Changes in the absorption spectra of NU02 of 2.5x10-2
M and with
1 equiv. n-BuNH2. Inset: the reaction picture at 0 and 120 min
0 min 120 min
58
Then, we varied the number equivalent of acid in 3 conditions
including 1 equiv, 10 equiv and 100 equiv as shown in Figure 4.31.
Condition 3: 1 eq. NU-02 [2.5x10-2 M]: 3 eq. n- BuNH2: 1 eq. HCl
Condition 4: 1 eq. NU-02 [2.5x10-2 M :3 eq. n- BuNH2: 10 eq. HCl
Condition 5: 1 eq. NU-02 [2.5x10-2 M]: 3 eq. n- BuNH2: 100 eq. HCl
500 550 600 650 700
0.0
0.2
0.4
0.6
0.8
1.0
No
rma
lize
d A
bso
rba
nce
In
ten
sity
(a
.u.)
Wavelength (nm)
0 min
5 min
30 min
60 min
120 min
500 550 600 650 700
0.0
0.2
0.4
0.6
0.8
1.0
No
rma
lize
d A
bso
rba
nce
In
ten
sity
(a
.u.)
Wavelength (nm)
0 min
5 min
20 min
60 min
120 min
450 500 550 600 650 700
0.0
0.2
0.4
0.6
0.8
1.0
No
rma
lize
d A
bso
rba
nce
In
ten
sity
(a
.u.)
Wavelength (nm)
0 min
5 min
30 min
60 min
120 min
Figure 4.31 Changes in the absorption spectra of NU02 of 2.5x10-2
M and n-BuNH2
in CH3CN solution with (A) condition 3 (1 equiv HCl), (B) condition 4
(10 equiv HCl) and (C) condition 5 (100 equiv HCl). Inset: the reaction
picture at 0 and 120 min
(A)
(B)
(C)
0 min 120 min
0 min 120 min
0 min 120 min
59
Upon the addition of equivalent of HCl to the solution of NU02 and
butylamine, these results suggested that the 100 equiv. HCl gave a fast reaction with
more than 50 nm change from 528 to 450 nm. Hence, we conclude that NU02 can be
used as a colorimetric sensor toward n-BuNH2. Afterwards, we studied an equivalent of
n-BuNH2 with 100 eq. HCl as shown in Figure 4.32. The data shows the shifted maxima
absorption similar as 3 eq. of n-BuNH2.
Condition 6: 1 eq. NU-02 [2.5x10-2 M: 1 eq. n- BuNH2: 100 eq. HCl
450 500 550 600 650 700
0.0
0.2
0.4
0.6
0.8
1.0 0 min
5 min
30 min
60 min
120 min
Nor
mal
ized
Ab
sorb
ance
In
ten
sity
(a.
u)
Wavelength (nm)
Figure 4.32 Changes in the absorption spectra of NU02 of 2.5x10-2
M and n- BuNH2
in CH3CN solution with 100 equiv. HCl. Inset: the reaction picture
at 0 and 120 min
Then, we proved that reaction need n-BuNH2 to form a new
chromophore by using condition 7. The results conclude that a new chromophore doesn’t
observe with this condition (Figure 4.33).
Condition 7: 1 eq. NU-02 [2.5x10-2 M]: 100 eq. HCl withoutn n- BuNH2
500 550 600 650 700
0.0
0.2
0.4
0.6
0.8
1.0
0 min
5 min
30 min
90 min
120 min
Nor
mal
ized
Ab
sorb
ance
In
ten
sity
(a.
u.)
Wavelength (nm)
Figure 4.33 Changes in the absorption spectra of NU02 of 2.5x10-2
M and with
10 equiv. HCl. Inset: the reaction picture at 0 and 120 min
0 min 120 min
0 min 120 min
60
In addition, the changed absorption spectra suggested a formation
of new chromophore in the complex. The amide formation could be a responsible from
the ester functionalize moieties and amine analyze. Therefore, we synthesized and
studied the absorption the amide complex (KM10) as shown in Figure 4.34.
Figure 4.34 UVVis absorption spectra of NU02 and KM10 of 2.5x10-2
M in CH3CN
at room temperature. Inset: the picture at room temperature
The result shows that KM10 (516 nm) shows significantly blue
shifted compared with NU02 (536 nm). The observation showed similar
to imtermediate in the previous conditions. The colorimetric n-butylamine sensor data
are summarized in the Table 4.5.
Table 4.5 Summary of maximum absorption wavelength of NU02
NU02 : n-BuNH2 : HCl max (nm)
0 min 5 min 30 min 60 min 120 min
1). 1 eq. : 3 eq. :(excess)
2). 1 eq. : 1 eq. : 0 eq.
3). 1 eq. : 3 eq. : 1 eq.
4). 1 eq. : 3 eq. : 10 eq.
5). 1 eq. : 3 eq. : 100 eq.
6). 1eq. : 1 eq. : 100 eq.
7). 1 eq. : 0 eq. : 100 eq.
536
516
525
527
528
516
519
530
516
525
521
517
516
514
500
518
521
514
462
496
514
482
516
518
508
454
457
510
474
509
510
498
450
448
503
550 600 650 700
0.0
0.2
0.4
0.6
0.8
1.0 NU02
KM10N
orm
ali
zed
Ab
sorb
an
ce I
nte
nsi
ty (
a.u
.)
Wavelength (nm)
NU02 and KM10
61
From Table 4.5, the maximum absorption wavelength showed
significant change with the number of HCl. It was found that colormetric sensor was
changed from red to orange.
Afterwards, KM09 was used to study the effect of an electrophile
position. KM09, the ester moieties was placed with para position compared with NU02
(meta-position). The colorimetric n-butylamine sensor was investigated by KM09 with
100 eq. HCl by 1 eq. n-BuNH2. This reaction also was monitored by visible absorption
spectra as shown in Figure 4.35.
Condition 8: 1 eq. KM09 [2.5x10-2 M]: 1 eq. n-BuNH2: 100 eq. HCl
575 600 625 650 675 700
0.0
0.2
0.4
0.6
0.8
1.0 0 min
5 min
30 min
60 min
120 min
No
rma
lize
d A
bso
rba
nce
in
ten
sity
(a
.u.)
Wavelength (nm)
Figure 4.35 Changes in the absorption spectra of KM09 of 2.5x10-2
M and
100 equiv. HCl in CH3CN solution with 1 equiv.n-BuNH2.
Inset: the reaction picture at 0 and 120 min.
Upon addition of reaction time, the absorption wavelength do not
change until 2 hour supported by the unchange color. We conclude that the meta
electrophile position of ester moieties is a suitable position for amine colorimetric sensor.
0 min 120 min
62
CHAPTER 5
CONCLUSIONS
The two series of ionic cyclometalated Ir(III) complexes compose of OLEDs and
colorimetric n-butylamine sensor.
First series, the complexes used for organic light emitting diode (OLEDs);
[Ir(spiro)(ppy)2]PF6 (KM01), [Ir(spiro)(thio)2]PF6 (KM02), [Ir(spiro)(difluoro)2]PF6
(KM03) and [Ir(spiro)(ppz)2]PF6 (KM04), which spiro is 4,5-diaza-9,9´-spirobifluorene,
ppy is 2-phenylpyridine, thio is 2-thiophenyl pyridine, difluoro is 2´,4´-difluorophenyl-
pyridine and ppz is 2´,4´-difluorophenyl 1H-pyrazole. The complexes have been
successfully synthesized. All complexes were characterized by NMR, MS, UV-Vis,
PL and CV. The charged iridium (III) complexes successfully generated emission color
from green, yellow and orange (501-582 nm). Then, KM01-KM04 were fabricated
to OLEDs device based on ITO/PEDOT:PSS/KM01-KM04:BMIMPF6 (1:1 by mole)/
TPBi/LiF/Al in acetronitrile solvent. From the results, KM01-KM04 showed
maximum current efficiency at 1.72, 0.07, 1.68, 0.19 cd/A and brightness at 2,027,
130, 879, 27 cd/m2, respectively. We found that KM01 showed maximum current
efficiency at 1.72 cd/A, brightness at 2,027 cd/m2 and CIE coordinates of (0.48, 0.50).
To improve a performance, KM04 was studied with a co-solvent as acetonitrile and
1,2 dichlorobenzene (1:1 v/v) and modified ratio of ionic liquid to (1:0.75).
We found that the better electroluminescence device can be obtained with the current
efficiency to 0.29 cd/A, the maximum brightness at 212 cd/m2.
Second series, the complexes used for colorimetric n-butylamine sensor;
[Ir(L1)(ppy)2]PF6 (NU02) and [Ir(L2)(ppy)2]PF6 (KM09). Which L1 is dimethyl-
2,2´-bipyridine-3,3´-dicarboxylate and L2 is dimethyl-2,2´bipyridine-4,4´dicarboxylate.
We studied the colorimetric n-butylamine sensor by varied the amount of HCl and
n-butylamine. From the studied, the condition of NU02 with 100 equiv. of HCl
changed the color from red to orange after 120 minutes of reaction. The results showed
63
that the absorption bands of KM09 do not change in reaction. Moreover,
we synthesized and studied KM10 which suggested a formation of new chromophore
compared with NU02. This preliminary study could be a benefit system to detect many
narcotic drugs in the future.
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APPENDICES
71
APPENDIX A
Characterization data
72
4000 3500 3000 2500 2000 1500 1000 500
70
75
80
85
90
95
100
3397
A4
% T
ran
smit
tan
ce
Wavenumber (cm-1)
3071
1726
17001623 1395
1220
1065
1137
778
Figure A.1 13
C NMR in DMSO, ATR-FTIR (neat) and mass of A4 at room
temperature
73
4000 3500 3000 2500 2000 1500 1000 500
50
60
70
80
90
100
L1
% T
ran
smit
tan
ce
Wavenumber (cm-1)
3004
2847
1711
1599
1412
1296
1131
762
Figure A.2 13
C NMR in CDCl3 and ATR-FTIR (neat) of L1 at room temperature
74
4000 3500 3000 2500 2000 1500 1000 500
50
60
70
80
90
100
110
YN-13
% T
ran
smit
tan
ce
Wavenumber (cm-1)
3112
2437
1706
1603
1458
1285
1012
755
680
Figure A.3 13
C NMR in DMSO, ATR-FTIR (neat) and mass of YN-13 at room
temperature
75
4000 3500 3000 2500 2000 1500 1000 500
40
50
60
70
80
90
100
110
L2
% T
ran
smit
tan
ce
Wavenumber (cm-1)
3000
29202845
1727
1589
1433
1290
1123
953
747
Figure A.4 13
C NMR in CDCl3, ATR-FTIR (neat) and mass of L2 at room
temperature
76
4000 3500 3000 2500 2000 1500 1000 500
30
40
50
60
70
80
90
100
110
L3
% T
ran
smit
tan
ce
Wavenumber (cm-1)
3252
3069
2957
2867
1631
1579
1411
1316
774
Figure A.5 13
C NMR in DMSO, ATR-FTIR (neat) and mass L3 at room
temperature
77
4000 3500 3000 2500 2000 1500 1000 500
40
50
60
70
80
90
100
110
KM01
% T
ran
smit
tan
ce
Wavenumber (cm-1)
3039
1603
1476
1414
1158 1020
754
Figure A.6 ATR-FTIR (neat) and mass of KM05 at room temperature
78
4000 3500 3000 2500 2000 1500 1000 500
50
60
70
80
90
100
110
KM02
% T
ran
smit
tan
ce
Wavenumber (cm-1)
3057
1601
1470
1152
883
774
Figure A.7 ATR-FTIR (neat) and mass of KM06 at room temperature
79
4000 3500 3000 2500 2000 1500 1000 500
30
40
50
60
70
80
90
100
110
KM03
% T
ran
smit
tan
ce
Wavenumber (cm-1)
3086
1599
1477
12941262
1112
826
753
Figure A.8 ATR-FTIR (neat) and mass of KM07 at room temperature
80
4000 3500 3000 2500 2000 1500 1000 500
60
70
80
90
100
110
KM04
% T
ran
smit
tan
ce
Wavenumber (cm-1)
3086
1613
1480
12571107
1031
817
750
Figure A.9 ATR-FTIR (neat) and mass of KM08 at room temperature
81
4000 3500 3000 2500 2000 1500 1000 500
40
50
60
70
80
90
100
NU02
% T
ran
smit
tan
ce
Wavenumber (cm-1)
3085
1731
2923
1600
1412
1305
1296
830
758
Figure A.10 ATR-FTIR (neat) and mass of NU02 at room temperature
82
4000 3500 3000 2500 2000 1500 1000 500
40
50
60
70
80
90
100
110
KM05
% T
ran
smit
tan
ce
Wavenumber (cm-1)
30432921
1729
16071478
1261
1122
830
753
Figure A.11 1H NMR in CDCl3, ATR-FTIR (neat) and mass of KM09 at room
temperature
83
4000 3500 3000 2500 2000 1500 1000 500
30
40
50
60
70
80
90
100
KM07
Wavenumber (cm-1)
% T
ran
smit
tan
ce
3428
3063
2923
1661
1607
1478
13121151
825
755
Figure A.12 ATR-FTIR (neat) and mass of KM10 at room temperature
84
4000 3500 3000 2500 2000 1500 1000 500
30
40
50
60
70
80
90
100
110
KM08
% T
ran
smit
tan
ce
Wavenumber (cm-1)
3037
3607
1478
1163
835
725
Figure A.13 13
C NMR in CDCl3, ATR-FTIR (neat) and mass of KM01at room
temperature
85
4000 3500 3000 2500 2000 1500 1000 500
20
30
40
50
60
70
80
90
100
KM09
% T
ran
smit
tan
ce
Wavenumber (cm-1)
2950
2855
1604
1473
1157
830
721
Figure A.14 13
C NMR in CDCl3 and ATR-FTIR (neat) and mass of KM02
at room temperature
86
4000 3500 3000 2500 2000 1500 1000 500
20
30
40
50
60
70
80
90
100
110
KM10
% T
ran
smit
tan
ce
Wavenumber (cm-1)
3087
1602
1478
1248
1105
817
729
Figure A.15 13
C NMR in CDCl3, ATR-FTIR (neat) and mass of KM03
at room temperature
87
4000 3500 3000 2500 2000 1500 1000 500
20
30
40
50
60
70
80
90
100
110
KM11
% T
ran
smit
tan
ce
Wavenumber (cm-1)
2928
2862
1615
1416
1258 1108
1037
838
725
Figure A.16 13
C NMR in CDCl3, ATR-FTIR (neat) and mass of KM04 at room
temperature
88
APPENDIX B
Conference and publications
89
Oral presentation
The 2013 3rd International Conference on Advanced Materials and Engineering
Materials (3rd ICAMEM 2013) in the title of A Novel charge iridium(III) complex
for amine sensor application, during December 14th-15th, 2013 in Singapore.
90
Publication papers
91
92
93
94
CURRICULUM VITAE
NAME Miss Kattaliya Mothajit
BIRTH DATE 24 June 1989
BIRTH PLACE Sisaket Province, Thailand
EDUCATION B. Sc. (Chemistry), Department of
Chemistry, Faculty of Science, Ubon
Ratchathani University, Ubon
Ratchathani, Thailand, 2008-2011.
M. Sc. (Chemistry), Department of
Chemistry, Faculty of Science, Ubon
Ratchathani University, Ubon
Ratchathani, Thailand, 2011-2015.
RESEARCH GROUP Organometallic and Catalytic Center (OCC)