minor research project [12 mrp-1872/14-15/klmg016/ugc...
TRANSCRIPT
Theoretical Investigation of Non Linear Optical Properties of Molecules Containing Naphthalene Linked to Nitrophenyl Group
MINOR RESEARCH PROJECT [12th PLAN]
MRP-1872/14-15/KLMG016/UGC-SWRO
SUBMITTED TO
UNIVERSITY GRANTS COMMISSSION
PRINCIPAL INVESTIGATOR
ANJU LINDA VARGHESE
Assistant Professor Department of Chemistry
Catholicate College Pathanamthitta, Kerala
1
DECLARATION
I hereby declare that the minor research project “Theoretical Investigation of Non Linear
Optical Properties of Molecules Containing Naphthalene Linked to Nitrophenyl Group”is
an original record of studies and research carried out by me during the tenure of the project.
Date: 17 -02- 2017 Principal Investigator
Place: Pathanamthitta
ANJU LINDA VARHGESE
2
Date: 17 February 2017
CERTIFICATE
This is to certify that the Minor Research Project entitled “Theoretical Investigation of Non
Linear Optical Properties of Molecules Containing Naphthalene Linked to Nitrophenyl
Group”MRP-1872/14-15/KLMG016/UGC-SWRO submitted to University Grants Commission
is a bonafidework by ANJU LINDA VARHGESE of our institution.
Principal/Registrar Principal Investigator
3
Contents Page number
Chapter 1: Introduction 1
1.1 Linear Optical Properties 2
1.2 Non Linear Optical Properties 3
1.3 Density Functional Calculations 4
1.4 Basis sets 5
1.5 Objectives 9
Chapter 2: Experimental Section 10
2.1 Computational Details 11
2.2 Chemicals 11
2.3 Synthesis of N-(2,4-dinitrophenyl)naphthalene-1-amine 11
2.4 Characterization Techniques 12
Chapter 3: Results and Discussions 13
3.1 DFT studies on the electronic transitions of N-[3-(Naphthalene-1-yloxy)butyl]-2,4-dinitroaniline, N-[3-(Naphthalene-1-yloxy)butyl]-4-nitroaniline, and their azanaphthalene derivatives
14
3.2 DFT studies on the Non Linear Optical Properties of the above molecule and their structural relationships.
21
4
3.3 DFT studies on the electronic transitions of N-[3-(Quinoline-1-yloxy)butyl]-2,4-dinitroaniline , N-[3-(Quinoline-1-yloxy)butyl]-4-nitroaniline, and their position isomers
28
3.4 DFT studies on the electronic transitions of N-[3-(Quinoline-1-yloxy)butyl]-2,4-dinitroaniline , N-[3-(Quinoline-1-yloxy)butyl]-4-nitroaniline, and their position isomers
34
3.5 DFT studies on the electronic transitions of N-[(Naphthalen-5-yl)methyl]-4 nitrobenzamine and N-[(Naphthalen-5-yl)methyl]-2,4 dinitrobenzamine
36
3.6 DFT studies on the nonlinear optical properties of N-[(Naphthalen-5-yl)methyl]-4 nitrobenzamine and N-[(Naphthalen-5-yl)methyl]-2,4 dinitrobenzamine
38
3.7 DFT studies on the electronic transitions of N-(4-Nitrophenyl)naphthalene-1-amine and N-(2,4-dinitrophenyl)naphthalene-1-amine
39
3.8 DFT studies on the Nonlinear optical properties of N-(4-Nitrophenyl)naphthalene-1-amine and N-(2,4-dinitrophenyl)naphthalene-1-amine
41
3.9 Characterization Techniques 41
3.9.a FT-IR
CHAPTER 4 : Findings &Conclusions 43
4.1 Conclusions 44
4.2 References
ANNEXURE
46
48
5
CHAPTER 1
INTRODUCTION
6
THEORY OF LINEAR AND NONLINEAR OPTICS
Linear and nonlinear optics covers a variety of phenomena involving the interaction of
light with matter. The constantly growing application of optics in technology,
telecommunication, medicine, etc. demanding detailed theoretical modeling, has opened new
fields for theoretical study. Understanding both the linear and nonlinear optical properties of
solids requires a detailed quantum mechanical picture of how electrons move in these materials.
This is an important emerging area of theoretical science.
Most familiar optical processes are proportional to light intensity. But, since the
late1960’s a variety of exciting nonlinear (scaling as the second, third etc. order of the light
intensity) optical phenomena have been discovered experimentally using powerful lasers [1, 2].
These so called many photon effects (second, third, and even higher order harmonic and sum
frequency generation, optical rectification, etc.) have found numerous applications. The
theoretical description of the linear and nonlinear optical properties of solids requires both
convenient and correct formalism, and a detailed quantum mechanical description of the many-
particle systems.
1.1 LINEAR OPTICAL PROPERTIES
The various ways in which light interacts with matter are of immense practical interest
e.g. absorption, transmission, reflection, scattering or emission. These properties are energy
dependent. The study of optical properties of solids has proven to be a powerful tool in our
understanding of the electronic properties of materials. In particular structure, energy
dependence of the properties mentioned above is in an intricate way related to the band structure.
Information on energy eigenvalues and Eigen function is needed to calculate the frequency /
energy dependent optical properties. When light of sufficient energy shines on a material, it
induces transitions of electrons from occupied states (below Fermi Energy, EF) to unoccupied
states (above EF). Clearly a quantitative study of these transitions must provide some
understanding of the position of the initial and the final energy bands and symmetry of their
associated wave functions.
7
1.2 Nonlinear optical properties A material interacting with intense light of a laser beam responds in a “nonlinear
fashion”. Consequences of this are a number of peculiar phenomena, including the generation of
optical frequencies that are initially absent. This effect allows the production of laser light at
wavelengths normally unattainable by conventional laser techniques. So the applications of Non
Linear Optics (NLO) range from basic research to spectroscopy, telecommunications and
astronomy.
Second harmonic generation (SHG), in particular, corresponds to the appearance of a
frequency component in the laser beam that is exactly twice the input one. SHG has great
potential as a characterization tool for materials, because of its sensitivity to symmetry. Today
SHG is widely applied for studying the surfaces and interfaces. For materials with bulk inversion
symmetry, SHG is only allowed at surfaces and interfaces. This makes SHG a powerful surface
selective technique. In case of embedded interfaces this technique gains extra weight when an
intense laser is used which is capable of penetrating deep into the material and no direct contact
with the sample is needed. In the case of linear optical transitions, an electron absorbs a photon from the incoming
light and makes a transition to the next higher unoccupied allowed state. When this electron
relaxes it emits a photon of frequency less than or equal to the frequency of the incident light
(Figure 1.a). SHG on the other hand is a two-photon process where this excited electron absorbs
another photon of same frequency and makes a transition to reach another allowed state at higher
energy. This electron when falling back to its original state emits a photon of a frequency which
is two times that of the incident light (Figure1.b). This results in the frequency doubling in the
output.
Figure 1. Schematic representation of (a) linear optical transition and
(b) second harmonic generation
8
In order to extend the use of NLO for understanding the properties of surfaces and for
extracting maximal information from such measurements for non centro-symmetric materials, a
more quantitative theoretical analysis is required.
1.3 Density Functional Calculations Density functional calculations (often called density functional theory (DFT)
calculations) are, like ab initio and SE calculations, based on the Schrodinger equation.
However, unlike the other two methods, DFT does not calculate a wavefunction, but rather
derives the electron distribution (electron density function) directly. A functional is a
mathematical entity related to a function. Density functional calculations are usually faster than
ab initio, but slower than SE. DFT is relatively new (serious DFT computational chemistry starts
in 1980' s, while computational chemistry with the ab initio and SE approaches was being done
in the 1960s).
Density functional theory is based on the Hohenberg-Kohn theorems, which state that,
“The ground-state properties of an atom or molecule are determined by its electron density
function, and that a trial electron density must give an energy greater than or equal to the true
energy”. DFT is not variational - it can give an energy below the true energy.
In the Kohn-Sham approach the energy of a system is formulated as a deviation from the
energy of an idealized system with non-interacting electrons. The energy of the idealized system
can be calculated exactly since its wavefunction (in the Kohn-Sham approach wavefunctions and
orbitals were introduced as a mathematical convenience to get at the electron density) can be
represented exactly by a Slater determinant. The relatively small difference between the real
energy and the energy of the idealized system contains the exchange-correlation functional, the
only unknown term in the expression for the DFT energy; the approximation of this functional is
the main problem in DFT. From the energy equation, by minimizing the energy with respect to
the Kohn-Sham orbitals, the Kohn-Sham equations (KS equations) can be derived, analogously
to the HF equations. The molecular orbitals of the KS equations are expanded with basis
functions and matrix methods are used to iteratively find the energy, and to get a set of molecular
orbitals, the KS orbitals, which are qualitatively similar to the orbitals of wave function theory.
The most popular current DFT method is the LSDA (Local Spin Density Approximation)
gradient-corrected hybrid method which uses the B3LYP (Becke three parameter Lee-Yang-
9
Parr) functional. For homolytic dissociation, correlated methods (e.g. B3LYP, pBP/DN* and
MP2) are vastly better than HF-level calculations; these methods also tend to give fairly good
activation barriers. DFT gives reasonable IR frequencies and intensities, comparable to those
from MP2 calculations. Dipole moments from DFT appear to be more accurate than those from
MP2. Time-dependent DFT (TDDFT) is the best method for calculating UV spectra reasonably
quickly. DFT is said to be better than HF (but not as good as MP2) for calculating NMR spectra.
1.4 Basis Sets An approximate wavefunction (eg. a Slater determinant) can be made up from MO’s
which are themselves approximated by atomic orbitals (LCAO). The AO’s are in turn
constructed from combinations of basis functions.
Basis functions AO’s MO’s Wave function
The list of all basis functions used in a calculation is called basis set.
The basis function model all the possible ways that electrons behave in a molecule. We should
include enough functions to model the orbital properly.
A basis set is a set of mathematical functions (basis functions), linear combinations of
which yield molecular orbitals. The functions are usually, but not invariably, centered on atomic
nuclei. Approximating molecular orbitals as linear combinations of basis functions is usually
called the LCAO or linear combination of atomic orbitals approach, although the functions are
not necessarily conventional atomic orbitals: they can be any set of mathematical functions that
are convenient to manipulate and which in linear combination give useful representations of
MOs. With this reservation, LCAO is a useful acronym. Physically, several (usually) basis
functions describe the electron distribution around an atom and combining atomic basis functions
yields the electron distribution in the molecule as a whole.
The electron distribution around an atom can be represented in several ways. Hydrogen-
like functions based on solutions of the Schrodinger equation for the hydrogen atom, polynomial
functions with adjustable parameters, Slater functions, and Gaussian functions have all been
used. Of these, Slater functions (STOs) and Gaussian functions (GTOs) are mathematically the
simplest, and it is these that are currently used as the basis functions in molecular calculations.
Slater functions are used in semi-empirical calculations. Modern molecular ab initio programs
employ Gaussian functions.
10
Slater Type Orbitals (STO) defined as,
Gaussian Type Orbitals (GTO) defined as,
where the radial part of the function, N is the
normalization factor, n is principal quantum number, is the angular part (spherical
harmonics), and Slater and Gaussian functions are usually characterized by parameters
designated ζ (zeta) and α, respectively.
Exponent ζ determines how fast or slow the basis function decays away from the atom.
Big ζ = fast decay = function close to nucleus; small ζ = slow decay = function far from nucleus.
The GTF’s have zero slope and no cusp at the nucleus. So GTF’s have problems
representing the proper behavior near the nucleus. GTF’s fall off too rapidly away from the
nucleus and the “tail” of the wave function is consequently represented poorly.
These problems can be solved by adding together several primitive Gaussians, called a
contraction, with different exponents and coefficients into one basis function to approximate the
shape.
1.4. a. Minimal Basis set
This basis set consists of one function each for the core orbitals and valence orbitals (whether
occupied or not).
Hydrogen 1s = one basis function; Fluorine 1s + 2s +2px + 2py + 2pz = five basis functions.
Carbon 1s + 2s +2px + 2py + 2pz = five basis functions. Unoccupied valence p orbital also
counted.
Iron 1s, 2s, 2px, 2py, 2pz, 3s, 3px, 3py, 3pz, 3dxy, 3dxz, 3dyz, 3dx2, 3dy2, 3dz2, 4s,
4px,4py,4pz = 19 basis functions.
For example, “STO-3G” is short-hand for a minimal basis set in which each basis function is a
contraction of three primitive Gaussians. The minimal basis sets are good for rough and quick
calculations, but are not very accurate.
11
1.4. b. Multi zeta Basis sets: To overcome the deficiencies of the minimal basis set other basis
sets have been developed.
• Double zeta basis sets: These have twice the number of functions for each
orbital. Thus hydrogen would have two functions, carbon and oxygen 10
functions each.
• Triple zeta basis sets have thrice the number of functions compared to minimal
basis set.
• Split valence basis set developed by Pople have single function for the core, the
valence functions are split into double zeta or triple zeta type.
For example, “6-31G” basis set for fluorine: 1s orbital described by 6 primitive Gaussians
contracted to one basis function, One set of 2s and 2p orbitals described by contraction of 3
primitive Gaussians, One set of 2s and 2p orbitals described by 1primitive Gaussian That is 1
function for the core + 2 functions each for the valence 2s, 2px, 2py and 2pz orbitals. i.e. 9
functions after contraction.
6-311G means one basis function each for the core orbitals and three basis functions each for the
valence orbitals with contractions of 6,3 ,1 and 1 primitives respectively.
• Polarisation functions are functions of higher angular momentum used to account for
the polarization of atoms that occurs when forming chemical bonds. Usually p functions
are used to polarises electrons, d functions to polarise p electrons and f functions to
polarise d electrons.
e.g. p functions for H or d functions for carbon
The notation 6-31G(d) (or 6-31G*) implies a 6-31G basis set to which a set of
polarization functions added to heavier atoms (non hydrogen atoms). The notation 6-
31G(d,p) (or 6-31G**) implies a 6-31G basis set to which a set of d polarization
functions added to heavier atoms and a set of p functions on hydrogen atom.
• Diffuse functions are polarisation functions which have a small exponent to describe the
electron density away from the nucleus (eg for anions and weakly bonded molecules).
They are indicated by a + symbol in the notation. Eg. 6-31++G(d) includes a set of
polarisation functions on heavy atoms and hydrogen. The choice of the basis set is
dependent on the problem being considered and the availability of computational
resources.
12
Nonlinear optical (NLO) materials play a pivotal role in the future evolution of nonlinear
optics in general and have a great impact on information technology and industrial applications.
The understanding of the polarization mechanism and their relation to structural characteristics
of the materials has been improved. So the goal is to find and develop materials presenting large
nonlinearities. Last decade witnessed the development of new nonlinear optical materials of
inorganic, organic and semi-organic types. Organic nonlinear optical materials have potentially
high nonlinearities and rapid response [3]. They offer high degree of synthetic flexibility to tailor
their optical properties through structural modification. Organic molecule possessing a
conjugated system with a strong π-electron delocalization can have a large optical nonlinearity.
The delocalization of the π-electrons can be further enhanced by the addition of donor and
accepter groups at the opposite ends of the conjugated system. The strong charge transfer
between such groups operating across the entire extended system markedly adds to the optical
nonlinearity of the structure [4].
The polarizability of naphthalene containing systems has been extensively studied with
different theoretical methods and is found to have good nonlinear response. An attractive method
to modulate electron density distribution in this conjugated system is the direct incorporation of
functional groups (spacers) into its backbone. Such studies are done on conjugated oligomers and
polymers [5, 6]. But donor-acceptor systems containing naphthalene incorporated with spacer
groups in the backbone are largely unexplored.
The principal aim of the project is to undertake an exhaustive theoretical investigation on
the structural, electronic and dynamic properties of naphthalene system linked to nitrophenyl
Group, incorporated with spacer groups into its backbone. The molecules with beneficial
properties can be developed into NLO materials having potential applications in the
optoelectronic devices of telecommunications, information storage, optical switching and
photovoltaic devices like solar cells. We propose to investigate molecules in which naphthalene
group is connected to dinitro and mono-nitrophenyl groups in which the liking groups are
saturated carbon chain.
13
1.5 OBJECTIVES
DFT studies on the electronic transitions of N-[3-(Naphthalene-1-yloxy)butyl]-2,4-
dinitroaniline, N-[3-(Naphthalene-1-yloxy)butyl]-4-nitroaniline, and their azanaphthalene
derivatives.
DFT studies on the Non Linear Optical Properties of N-[3-(Naphthalene-1-yloxy)butyl]-
2,4-dinitroaniline, N-[3-(Naphthalene-1-yloxy)butyl]-4-nitroaniline, and their
azanaphthalene derivatives and their structural relationships.
DFT studies on the electronic transitions of N-[3-(Quinoline-1-yloxy)butyl]-2,4-
dinitroaniline , N-[3-(Quinoline-1-yloxy)butyl]-4-nitroaniline, and their position isomers.
DFT studies on the Non Linear Optical Properties of N-[3-(Quinoline-1-yloxy)butyl]-2,4-
dinitroaniline , N-[3-(Quinoline-1-yloxy)butyl]-4-nitroaniline, and their position isomers
DFT studies on the electronic transitions of N-[(Naphthalen-5-yl)methyl]-4
nitrobenzamine and N-[(Naphthalen-5-yl)methyl]-2,4 dinitrobenzamine.
DFT studies on the Non Linear Optical Properties of N-[(Naphthalen-5-yl)methyl]-4-
nitrobenzamine N-[(Naphthalen-5-yl)methyl]-2,4 dinitrobenzamine.
DFT studies on the electronic transitions of N-(4-Nitrophenyl)naphthalene-1-amine and
N-(2,4-dinitrophenyl)naphthalene-1-amine
DFT studies on the Non Linear Optical Properties of N-(4-Nitrophenyl)naphthalene-1-
amine and N-(2,4-dinitrophenyl)naphthalene-1-amine
Synthesis and characterization of N-(2,4-dinitrophenyl)naphthalene-1-amine.
14
CHAPTER 2
EXPERIMENTAL SECTION
15
2.1 Computational Details
Gaussian 09 software package was used for DFT calculation and calculations were
performed at B3LYP/6-31G(d,p) level. The ground state structures were optimized and
frequency calculations were performed to ensure that the optimized structures are minima in the
potential energy surface. HOMO and LUMO for all the molecules are identified. Gauss View 5
software was used for generating the input file and visualization of the results. The calculation
were done using S20D300 workstation computer equipped with Intel 7 core processor and 24 GB
RAM and Microsoft Windows as the operating system. Electric dipole moment, linear
polarizability and first hyperpolarizability tensor components for the studied compounds were
calculated by DFT approach which is currently one of the ultimate procedure for obtaining
numerically accurate NLO response.
2.2 Chemicals
1-Naphthylamine, 1-Fluoro-2,4-Dinitrobenzene and acetonitrile were purchased from Merck,
NH2
1-Naphthylamine NO2
NO2
F
1-Fluoro-2,4-Dinitrobenzene
2.3. Synthesis of N-(2, 4-dinitrophenyl)naphthalene-1-amine
Synthesis is based on the following equation.
NH2
NO2
NO2
F
+NaHCO3Acetonitrile
HN NO2
NO2
16
1 mol of 1-Naphthylamine(1.42 g) and 1 mol of 1-Fluoro-2,4-Dinitrobenzene (1 g) were taken in
250 ml RB flask.25 ml acetonitrile is added to it. The reaction mixture is refluxed at 80˚C for 10
hours. After refluxing, the reaction mixture is added to ice cold water. Reaction completion is
confirmed by TLC. N-(2,4-dinitrophenyl)naphthalene-1-amine is purified by Column separation.
Its formation is confirmed by FT-IR Spectrum.
2.4 Characterization Techniques
FT-IR: FT-IR spectra were recorded in the transmission mode using KBr pellets on Perkin
Elmer spectrometer operating at 4 cm-1 resolution at a range of 750 cm-1 to 4000 cm-1.
17
CHAPTER 3 RESULTS AND DISCUSSIONS
18
3.1 DFT studies on the electronic transitions of N-[3-(Naphthalene-1-yloxy)butyl]-2,4-dinitroaniline, N-[3-(Naphthalene-1-yloxy)butyl]-4-nitroaniline, and their azanaphthalene derivatives
The studied molecules are presented in Table 1-2.The study involves geometry optimization of the molecules, identifying its frontier molecular orbitals and energy gap. Electronic transitions of the following molecules are also discussed.
Figure 2. Schematic representation of naphthalene, quinoline, quinazoline, triaza naphthalene and tetraazanaphthalene derivatives linked to mononitrophenyl
R5
R8
R6
R7
R3
R2
R4
R1
O
CH3
NH
N+
O-
O Table 1. Structure of naphthalene, quinoline, quinazoline, triazanaphthalene and
tetraazanaphthalene derivatives linked to mononitrophenyl
No R1 R2 R3 R4 R5 R6 R7 R8 Name
1 C C C C C C C C N-[3-(Naphthalene-1-yloxy)butyl]-4-nitroaniline
2 C C C N C C C C N-[3-(Quinoline-4-yloxy)butyl]-4-nitroaniline
3 C N C N C C C C N-[3-(Quinazoline-1-yloxy)butyl]-4-nitroaniline
4 C N C N N C C C N-[3-(2,4,5TriazaNaphthalene-1-yloxy)butyl]-4-nitroaniline
5 C N C N N C N C N-[3-(2,4,5,7 TetraazaNaphthalene-1-yloxy)butyl]-4-nitroaniline
19
Figure 2. Schematic representation of naphthalene, quinoline, quinazoline, triazanaphthalene and tetraazanaphthalene derivatives linked to dinitrophenyl
R5
R8
R6
R7
R3
R2
R4
R1
O
CH3
NH
N+
O-
O
N+
O-
O Table 2. Structure of naphthalene, quinoline, quinazoline, triazanaphthalene and
tetraazanaphthalene derivatives linked to dinitrophenyl No R1 R2 R3 R4 R5 R6 R7 R8 Name 6 C C C C C C C C N-[3-(Naphthalene-1-yloxy)butyl]-2,4-dinitro
aniline 7 C C C N C C C C N-[3-(Quinoline-1-yloxy)butyl]-2,4-dinitro
aniline 8 C N C N C C C C N-[3-(Quinazoline-1-yloxy)butyl]-2,4-dinitro
aniline 9 C N C N N C C C N-[3-(2,4,5TriazaNaphthalene-1-yloxy)butyl]-
2,4-dinitroaniline 10 C N C N N C N C N-[3-(2,4,5,7 TetraazaNaphthalene-1-yloxy)
butyl]-2,4-dinitroaniline
20
3.1. a Geometry Optimization Several conformational isomeric cisoid and transoid structures of compound 1-10 were
optimized at B3LYP/6-31G (d,p) level. The lowest energy structures will be equilibrium
geometry of the molecules. The optimized molecular geometry (Fig.1-10) represents an isolated
molecule under ideal conditions with a stationary point at the potential energy surface. The
convergence was confirmed by observing no imaginary vibrational frequencies. All the
compounds in Table 1-2 show cisoid confirmation.
Table 3. Total energy and HOMO-LUMO gaps of compounds 1-5
Compound Total Energy Difference HOMO LUMO HLG
Hartrees kJ/Mol Hartrees Hartrees Hartrees eV 1
Cisoid
-1108.904369
10.75
-0.21101
-0.09895
0.11206
3.04
Transoid
-1108.908464
-0.20422
-0.07029
0.10397
3.64
2
Cisoid
-1124.962679
7.31
-0.22245
-0.07150
0.15095
4.11
Transoid
-1124.959894
-0.22341
-0.07283
0.15058
4.09
3
Cisoid
-1141.027722
6.14
-0.22071
-0.06992
0.1507
4.10
Transoid
-1141.025385
-0.22270
-0.07122
0.15148
4.12
4
Cisoid
-1157.07247
5.48
-0.22343
-0.07484
0.14859
4.04
Transoid
-1157.070381
-0.22519
-0.07327
0.15192
4.13
5
Cisoid
-1173.120091
6.04
-0.22564
-0.08870
0.13694
3.72
Transoid
-1173.117790
-0.22722
-0.08589
0.14133
3.85
21
Table 4. Total energy and HOMO-LUMO gaps of compounds 6-10
Compound Total Energy Difference HOMO LUMO HLG
Hartrees KJ/Mol Hartrees Hartrees Hartrees eV
1 Cisoid -1313..40761
8.77 -0.21101 -0.09895 0.11206 3.04
Transoid -1313.404273 -0.20722 -0.10325 0.10397 2.83
2 Cisoid -1329.456685
3.17 -0.23054 -0.10292 0.1276 3.47
Transoid -1329.455476 -0.22671 -0.10588 0.1208 3.29
3 Cisoid -1345.522103
2.66 -0.24403 -0.10254 0.1415 3.85
Transoid -1345.521089 -0.24202 -0.10410 0.1379 3.75
4 Cisoid -1361.56655
1.68 -0.24721 -0.10526 0.1419 3.86
Transoid -1361.565912 -0.24870 -0.10621 0.1425 3.87
5 Cisoid -1377.613794
3.8 -0.24817 -0.10589 0.1423 3.87
Transoid -1377.612347 -0.24805 -0.1029 0.1452 3.95
From Tables 3 and 4, it is evident that all the compounds in Table 1-2 show cisoid
confirmation. The geometries were fully optimized without any constraint with the help of
analytical gradient procedure implemented within Gaussian 09 program. All the parameters were
allowed to relax and all the calculations converged to an optimized geometry which corresponds
to a true energy minimum revealed by the lack of imaginary values in the frequency calculations.
Their optimized structure and structures of Frontier Molecular Orbitals (HOMO-LUMO) are
listed in Tables 5 and 6.
Their study demonstrated that there are significant differences in the structure of these
compounds related to the geometry of the naphthalene or azanaphthalene group. These
compounds may be divided into two groups: the first group, naphthalene or azanaphthalene, is
coplanar with spacer group. The second group, nitrophenyl, is twisted with respect to the spacer.
Theoretically, the torsional angles between the planes of the donor and acceptor subunits are
calculated. Also the optimized structure reveals that naphthalene/azanaphthalene linked to
mononitrophenyl are having more delocalization than naphthalene /azanaphthalene linked to
dinitrophenyl group. Effective distance between two rings in all 10 components were estimated
22
which is enlisted in Table 9. From this table, we can understand that effective distance between
two rings for mononitro derivatives were larger than dinitro derivatives. It reveals that mononitro
derivatives are having more delocalization than dinitro derivatives.
Table 5. Optmised structure of compound 1-10 Optimized structure of the aforementioned compounds are listed in Table 5.
23
Compound 1
Compound 6
Compound 2
Compound 7
Compound 3
Compound 8
Compound 4
Compound 9
Compound 5
Compound 10
24
Table 6. HOMO-LUMO Orbitals of compound 1-10
Compound HOMO Orbital LUMO Orbital
1
2
3
4
5
6
25
7
8
9
10
DFT and TDDFT calculations were performed on the 10 molecule which contain an
electron donor and electron acceptor which are linked together by saturated carbon chain. The
most stable conformations are cisoid confirmation for all ten compounds. The electronic
excitation occurs by the transfer of an electron from the HOMO or HOMO-1 orbital to LUMO
+1 orbital in all the ten compounds. The HOMO-LUMO gaps of the most stable conformations
of the ten compounds are close. The emission takes place by the transfer of an electron to the
LUMO orbital.
3.2. DFT studies on the Non Linear Optical Properties of the above molecule and their structural relationships.
The performance of various DFT functional and of basis sets in hyperpolarizability
calculations have been extensively studied for organic NLO materials [7-10]. The nonlinear
26
optical properties of donor acceptor derivatives of naphthalene and azanaphthalenes were
computed for different approximations of exchange and correlations because the quality of
approximation might have an important effect in DFT for such hydrogen-bonded systems [11].
BPV86, which uses Perdew’s 1986 functional with local correlation replaced by that which was
suggested Vosko et al. (VWN)[12-14]. Becke’s three parameter exchange functional and the
gradient corrected functional of Lee, Yang and Parr, B3LYP [12, 15, 16] and LSDA were used in
this study. Accurate calculation of nonlinear optical properties requires the use of extended basis
sets and a high level of theory. In particular, these basis sets have to include d and p polarization
functions together with s and p diffuse functions. In the present work, the 6-31G(d, p) [17-19]
basis set was chosen for calculation of static polarizability,
The nonlinear optical response of an isolated molecule in an electric field Ei can be presented as
a Taylor series expansion of the total dipole moment, μtot, induced by the field:
0
( ) ( )
1 1 .........,2! 3!
E E
E E E E E E
λ λ
λ λ λσ σ λσν σ ν λσνρ σ ν ρ
µ ψ µ ψ
µ µ α β γ
∧
=
= + + + +
Where, αis the linear polarizability, μ0 the permanent dipole moment and βis the first
hyperpolarizability tensor components. The isotropic (or average) linear polarizability and
anisotropy of polarizability is defined as [20]:
Isotropic linear Polarizability, 13 ( )xx yy zzα α α α= + +
Anisotropic linear Polarizability, 122 2 21
2 [( ) ( ) ( ) ]xx yy xx zz yy zzα α α α α α α∆ = − + − + −
The complete equation for calculating the total static first hyperpolarizability magnitude of
Gaussian output is given as follows [21]
First order Hyperpolarizability, 1
22 2 2[( ) ( ) ( ) ]tot xxx xyy xzz yyy yzz yxx zzz zxx zyyβ β β β β β β β β β= + + + + + + + +
The study involves the initial determination of static polarizabilities and hyperpolarizibilities in
the gas phase.
27
Naphthalene/ Azanaphthalene linked to mononitrophenyl ring
Nonlinear optical properties are calculated at DFT level using 6-31G (d, p) basis set using 3
hybrid functionals like B3LYP, BPV86 and LSDA. The calculated dipole moment, static mean
polarizabilities, anisotropy of polarizabilities and total first hyperpolarizibilities of the studied
compounds (1-5) are listed in Table 7a,7b,7c.and compounds 6-10 are enlisted in Table 7d,7e,7f.
Table 7a. NLO Properties of Naphthalene/ Azanaphthalene linked to mononitrophenyl ring using B3LYP
Compound μ ˂α˃ a.u Δα a.u βtot a.u. 1 7.68 246.89 209.43 2026.33 2 5.47 243.02 283.31 2339.59 3 7.56 237.98 275.56 2386.48 4 6.67 232.69 268.37 2306.04 5 5.68 225.93 186.68 1963.41
Table 7b. NLO Properties of Naphthalene/ Azanaphthalene linked to mononitrophenyl ring using BPV86
Compound μ ˂α˃ a.u Δα a.u βtot a.u. 1 7.41 256.34 228.12 2223.51 2 5.51 252.50 304.51 2536.11 3 7.57 247.57 297.27 2564.50 4 6.67 242.27 289.77 2474.84 5 5.69 235.61 207.31 1948.87
Table 7c. NLO Properties of Naphthalene/ Azanaphthalene linked to mononitrophenyl ring using LSDA
Compound μ ˂α˃ a.u Δα a.u βtot a.u. 1 7.53 256.81 230.35 2271.07 2 5.62 253.021 306.88 2565.48 3 7.74 248.13 299.84 2599.99 4 6.81 242.82 292.27 2499.03 5 5.77 236.22 210.093 1938.16
28
Table 7d. NLO Properties of Naphthalene/ Azanaphthalene linked to dinitrophenyl ring using B3LYP
Compound μ ˂α˃ a.u Δα a.u βtot a.u.
6 7.44 257.07 138.60 1467.67
7 7.05 257.86 236.46 1435.66
8 6.27 252.84 237.53 1528.13
9 5.56 247.75 229.99 1576.54
10 6.86 242.14 225.76 1543.95
Table 7e. NLO Properties of Naphthalene/ Azanaphthalene linked to dinitrophenyl ring using BPV86
Compound μ ˂α˃ a.u Δα a.u βtot a.u.
6 7.47 265.89 148.78 1579.02
7 7.03 267.38 250.26 1681.89
8 6.25 262.51 251.86 1856.31
9 5.63 257.42 244.099 1896.38
10 6.92 251.77 240.10 1820.16
Table 7f. NLO Properties of Naphthalene/ Azanaphthalene linked to dinitrophenyl ring using LSDA
Compound μ ˂α˃ a.u Δα a.u βtot a.u.
6 7.5835 266.34 150.15 1716.427
7 7.1259 268.01 252.03 1696.445
8 6.3503 263.18 253.72 1969.049
9 5.6991 258.07 245.89 2000.946
10 7.0256 252.45 241.98 1909.016
The discussion will be focused mostly on the first hyperpolarizability because the main objective of this work is to describe a general mechanism for obtaining large first-order optical nonlinearities in substituted naphthalene and azanaphthalene derivatives.
29
Graph 1. Comparison of first hyperpolarizability for compounds 1-5
2 4
2400
3200
4000
hype
rpol
arizi
bility
COMPOUNDS
LSDA BPV86 B3LYP
Graph 2. Comparison of first hyperpolarizability for compounds 6-10
1 2 3 4 51400
1500
1600
1700
1800
1900
2000
Hype
rpol
arizi
biliti
es
compounds
B3LYP BPV86 LSDA
In particular, the results of the calculations showed that the magnitudes of hyperpolarizibilities
are mainly dependent on the degree of electron delocalization between the two rings. Optical
response properties are governed by the increasing of both conjugation length and strength of
donor and acceptor groups. Also, the nitrogen numbers, planarity of the rings with spacer and
30
positions on the naphthalene are very important for nonlinearity of the title molecules.
Theoretically, the torsional angles between the planes of the donor and acceptor subunits are
calculated. Angle between C11-O1-C7-C8 determines the planarity of naphthalene ring with
spacer. Also the distance between C7-C15 is measured. They are shown in Figure 3-4.The
torsional angles and effective distance between two rings are enlisted in Table 8.
Figure 4. Naphthalene/Azanaphthalene linked to mononitrophenyl ring
31
Figure 5. Naphthalene/Azanaphthalene linked to dinitrophenyl ring
Table 8. Comparison of first hyperpolarizability for compounds 1-10 using B3LYP, BPV86 and LSDA and some selected geometrical parameters. β (B3LYP) β (BPV86) β (LSDA) C7-C15 (Å) C11-O1-C7-C8 (˚)
1 2026.33 2223.519 2271.065 6.89 2.434
2 2339.597 2536.114 2565.476 6.47 1.434
3 2386.487 2564.504 2599.997 6.433 1.280
4 2306.046 2474.841 2499.029 6.435 1.679
5 1963.409 1948.879 1938.155 6.434 2.884
6 1467.674 1579.016 1716.427 4.503 1.273
7 1435.662 1681.891 1696.445 5.779 3.277
8 1528.128 1856.31 1969.049 5.891 0.900
9 1576.539 1896.384 2000.946 5.924 0.692
10 1543.95 1820.155 1909.016 5.979 0.978
32
From this table, it is evident that the effective distance between two rings for mononitro
derivatives are larger than dinitro derivatives. As the effective distance increases, it is believed
that the extent of delocalization increases. So mononitro compounds are having large β values
than dinitro compounds. Addition of nitrogen on naphthalene changes the torsional angle
between the two units. However in all 10 compounds, naphthalene ring remains coplanar with
the spacer group. Among 10 selected compounds, compound no.3 is having highest β.This can
be attributed to its large delocalization and coplanarity of the ring with the spacer group.
3.3 DFT studies on the electronic transitions of N-[3-(Quinoline-1-yloxy)butyl]-2,4-dinitroaniline, N-[3-(Quinoline-1-yloxy)butyl]-4-nitroaniline, and their position isomers
The studied molecules are presented in Table 10-11.The study involves geometry optimization of
the molecules, identifying its frontier molecular orbitals and energy gap. Electronic transitions of
the following molecules are also discussed.
Figure 6. Schematic representation of naphthalene, quinoline, quinazoline, triazanaphthalene and tetraazanaphthalene derivatives linked to mononitrophenyl
R5
R8
R6
R7
R3
R2
R4
R1
O
CH3
NH
N+
O-
O
33
Table 9. Structure of naphthalene, quinoline, quinazoline, triazanaphthalene and tetraazanaphthalene derivatives linked to mononitrophenyl
No R1 R2 R3 R4 R5 R6 R7 R8 Name
1 C C C N C C C C N-[3-( Quinoline-2-yloxy)butyl]-4-nitroaniline
2 C C C N C C C C N-[3-(Quinoline-4-yloxy)butyl]-4-nitroaniline
3 C C C N C C C C N-[3-( Quinoline-6-yloxy)butyl]-4-nitroaniline
4 C C C N C C C C N-[3-( Quinoline-8-yloxy)butyl]-4-nitroaniline Figure 7. Schematic representation of naphthalene, quinoline, quinazoline,
triazanaphthalene and tetraazanaphthalene derivatives linked to dinitrophenyl
R5
R8
R6
R7
R3
R2
R4
R1
O
CH3
NH
N+
O-
O
N+
O-
O Table 10. Structure of naphthalene, quinoline, quinazoline, triazanaphthalene and
tetraazanaphthalene derivatives linked to dinitrophenyl No R1 R2 R3 R4 R5 R6 R7 R8 Name 5 C C C N C C C C N-[3-( Quinoline-2-yloxy)butyl]-2,4-dinitroaniline 6 C C C N C C C C N-[3-(Quinoline-4-yloxy)butyl]- 2,4-dinitroaniline 7 C C C N C C C C N-[3-( Quinoline-6-yloxy)butyl]- 2,4-dinitroaniline 8 C C C N C C C C N-[3-( Quinoline-8-yloxy)butyl]- 2,4-dinitroaniline
34
3.3.a Geometry Optimization Several conformational isomeric cisoid and transoid structures of compound 1-10 were
optimized at B3LYP/6-31G(d,p) level. The lowest energy structures will be equilibrium
geometry of the molecules. The optimized molecular geometry (Fig.3-4) represents an isolated
molecule under ideal conditions with a stationary point at the potential energy surface. The
convergence was confirmed by observing no imaginary vibrational frequencies. All the
compounds in Table 10-11 show cisoid confirmation.
Table 11a. Total energy and HOMO-LUMO gaps of compounds 1-4 Compound Total Energy Difference HOMO LUMO HLG
Hartrees KJ/Mol Hartrees Hartrees Hartrees ev
1
Cisoid -1124.976148 5.8
-0.21541 -0.06594 0.14947 4.07 Transoid -1124.9739 -0.21645 -0.06504 0.1547 4.21
2
Cisoid -1124.962679 7.31
-0.22245 -0.07150 0.15095 4.11 Transoid -1124.959894 -0.22341 -0.07283 0.15058 4.09
3
Cisoid -1124.960421 4.3 -0.21812 -0.06774 0.15038 4.09 Transoid -1124.95878 -0.21799 -0.06729 0.1507 4.10
4
Cisoid -1124.957051 5.9 -0.20848 -0.05984 0.14864 4.04 Transoid -1124.95480 -0.20831 -0.05691 0.1514 4.12
Table 11b. Total energy and HOMO-LUMO gaps of compounds 5-8 Compound Total Energy Difference HOMO LUMO HLG
Hartrees KJ/Mol Hartrees Hartrees Hartrees ev
1
Cisoid -1329.44298 0.92 -0.2236 -0.09166 0.1319 3.59
Transoid -1329.44263 -0.2231 -0.09159 0.1315 3.57
2
Cisoid -1329.456685 3.17 -0.23054 -0.10292 0.12762 3.47
Transoid -1329.455476 -0.22671 -0.10588 0.12083 3.28
3
Cisoid -1329.4374 4.72 -0.21241 -0.09585 0.11656 3.17
Transoid -1329.4356 -0.21238 -0.09568 0.1167 3.18
4
Cisoid -1329.46789 1.15
-0.22613 -0.07930 0.1468 3.99
Transoid -1329.46745 -0.22604 -0.07928 0.1467 4.00
35
Table 12. Optimized structure of compound 1-8
Compound 6
Compound 5
Compound 7
Compound 6
Compound 8
Compound 7
Compound 9
Compound 8
36
Table 13. HOMO-LUMO Orbitals of compound 1-8
Compound HOMO Orbital LUMO Orbital 1
2
3
4
5
37
6
7
8
All the compounds show Cisoid confirmation and their energy gap between HOMO and LUMO is identified
38
3.3 DFT studies on the electronic transitions of N-[3-(Quinoline-1-yloxy)butyl]-2,4-dinitroaniline, N-[3-(Quinoline-1-yloxy)butyl]-4-nitroaniline, and their position isomers
The simplest polarizability, a, characterizes the ability of an electric field to distort the
electronic distribution of a molecule, that is, the molecule as a whole is perturbed. Consequently,
a change in the equilibrium nuclear geometry will take place as a result of the development of a
different potential-energy surface. The result would be a change in the vibrational and rotational
motions of the molecule.Clearly, an effect of such orientation redistribution cannot be ignored.
Higher order polarizabilities (hyperpolarizabilities β,γ. . .) which describe the non-linear
response of atoms and molecules are related to a wide range of phenomena from non-linear
optics to intermolecular forces, such as the stability of chemical bonds, as well as, the
conformation of molecules and molecular aggregates [23].
According to Buckingham [24] the polarizability tensors are formally defined by a Taylor
series expansion of the dipole moment of a molecule in the presence of an electric field E,
0
( ) ( )
1 1 .........,2! 3!
E E
E E E E E E
λ λ
λ λ λσ σ λσν σ ν λσνρ σ ν ρ
µ ψ µ ψ
µ µ α β γ
∧
=
= + + + +
Where, μ is the dipole polarizability, β is the hyperpolarizability and γ is the second
hyperpolarizability and so on.; These studies led to the fact that ab initio calculations of
polarizabilities and hyperpolarizabilities have become available through the strong theoretical
basis for analyzing molecular interactions. They made possible the determination of the elements
of these tensors from derivatives of the dipole moment with respect to the electric field. For
methods as the self-consistent field (SCF) for which the wave function obeys the Hellmann–
Feynman theorem, the derivative expression for the dipole is equivalent to the expectation value
[25]. Applying the rules of perturbation theory, α and β are determined from a knowledge of the
first-order wave function and γ from a knowledge of the second-order wave function. Thus they
may be calculated accurately at the self-consistent field level using the Hartree–Fock theory [26].
However, electron correlation can be very important [27, 28] depending on whether it is an open
or closed shell system [29,30].
39
Table 14a. NLO Properties of N-[3-(Quinoline-1-yloxy)butyl]-4-nitroaniline, and their position isomers
Compound μ ˂α˃ a.u Δα a.u βtot a.u.
1 8.0318 245.8515 306.8861 2118.192
2 5.4716 243.0167 283.3157 2339.597
3 9.8753 245.9185 309.2144 1777.295
4 8.8968 239.2811 233.0332 1981.583
Table 14b. NLO Properties of N-[3-(Quinoline-1-yloxy)butyl]-2,4-dinitroaniline, and their position isomers
Compound μ ˂α˃ a.u Δα a.u βtot a.u.
5 9.7377 262.4461 216.0226 1816.091
6 7.0527 257.8592 236.4552 1435.662
7 7.2650 260.5112 254.3742 2016.854
8 11.1655 259.1174 220.2316 1612.477
All the 8 compounds show high β values which means they can be developed into good NLO
materials.
40
3.5 DFT studies on the electronic transitions of N-[(Naphthalen-5-yl)methyl]-4-nitrobenzamine and N-[(Naphthalen-5-yl)methyl]-2,4 dinitrobenzamine
HN
NO2
N-[(Naphthalen-5-yl)methyl]-4 nitrobenzamin
HN
NO2
NO2
N-[(Naphthalen-5-yl)methyl]-2,4 dinitrobenzamine
3.5.1 Geometry Optimization
Several conformational isomeric cisoid and transoid structures of compound 1 and 2
were optimized at B3LYP/6-31G(d,p) level. The lowest energy structures will be equilibrium
geometry of the molecules. The optimized molecular geometry (Fig.8) represents an isolated
molecule under ideal conditions with a stationary point at the potential energy surface. The
convergence was confirmed by observing no imaginary vibrational frequencies. All the
compounds in show cisoid confirmation.
Table 15. Total energy and HOMO-LUMO gaps of compounds 1-2 Compound Total Energy Difference HOMO LUMO HLG
Hartrees KJ/Mol Hartrees Hartrees Hartrees eV 1
Cisoid -915.83986 3.02 -0.21992 -0.06870 0.1512 4.11 Transoid -915.83871 -0.22202 -0.07044 0.1515 4.12
2
Cisoid -1120.34157 5.3
-0.23071 -0.09275 0.1379 3.75
Transoid -1120.322402 -0.23447 0.09085 0.1436 3.91
41
Table 16. Optimized structure of compound 1-2
N-[(Naphthalen-5-yl)methyl]-4 nitrobenzamine
N-[(Naphthalen-5-yl)methyl]-2,4 dinitrobenzamine
N-[(Naphthalen-5-yl)methyl]-4 nitrobenzamine and N-[(Naphthalen-5-yl)methyl]-2,4
dinitrobenzamine shows cisoid conformation. Their frontier molecular orbitals are identified and
they are enlisted in Table 18.
Table 17. HOMO-LUMO Orbitals of compound 1-2
Compound HOMO Orbital LUMO Orbital 1
2
42
3.6 DFT studies on the nonlinear optical properties of N-[(Naphthalen-5-yl)methyl]-4 nitrobenzamine and N-[(Naphthalen-5-yl)methyl]-2,4 dinitrobenzamine
The simplest polarizability, a, characterizes the ability of an electric field to distort the
electronic distribution of a molecule, that is, the molecule as a whole is perturbed. Consequently,
a change in the equilibrium nuclear geometry will take place as a result of the development of a
different potential-energy surface. The result would be a change in the vibrational and rotational
motions of the molecule. Clearly, an effect of such orientation redistribution cannot be ignored.
Higher order polarizabilities (hyperpolarizabilities β,γ. . .) which describe the non-linear
response of atoms and molecules are related to a wide range of phenomena from non-linear
optics to intermolecular forces, such as the stability of chemical bonds, as well as, the
conformation of molecules and molecular aggregates
Dipole moment, sotropic polarizability, anisotropic polarizability and hyper polarizability are
calculated using the aforementioned equation and were enlisted in Table 18.
Table 18: NLO properties of N-[(Naphthalen-5-yl)methyl]-4 nitrobenzamine and N-
[(Naphthalen-5-yl)methyl]-2,4 dinitrobenzamine
Compound μ ˂α˃ a.u Δα a.u βtot a.u. 1 7.3012 199.23 191.73 2518.743 2 8.0197 261.62 286.59 4748.619
N-[(Naphthalen-5-yl)methyl]-4 nitrobenzamine and N-[(Naphthalen-5-yl)methyl]-2,4
dinitrobenzamine show good nonlinear response.
43
3.7 DFT studies on the electronic transitions of N-(4-Nitrophenyl)naphthalene-1-amine and N-(2,4-dinitrophenyl)naphthalene-1-amine
HN
NO2
N-(4-Nitrophenyl)naphthalene-1-amine
HN
NO2
NO2
N-(2,4-dinitrophenyl) naphthalene-1-amine
Table 19. Total energy and HOMO-LUMO gaps of compounds 1-2
Compound Total Energy Difference HOMO LUMO HLG
Hartrees KJ/Mol Hartrees Hartrees Hartrees eV
1
Cisoid -876.55658 0.05 -0.21780 -0.07180 0.1460 3.97
Transoid -876.55656 -0.21781 -0.07179 0.1461 3.97
2
Cisoid -1081.05343 0.052 -0.22479 -0.10427 0.1205 3.28
Transoid -1081.05341 -0.22480 -0.10427 0.1205 3.28
N-(4-Nitrophenyl)naphthalene-1-amine and N-(2,4-dinitrophenyl)naphthalene-1-amine
show Cisoid conformation. Their HOMO-LUMO are identified.
44
Table 20. Optimized structure of compound 1-2
N-(4-Nitrophenyl)naphthalene-1-amine
N-(2,4-dinitrophenyl)naphthalene-1-amine
Table 21. HOMO-LUMO Orbitals of compound 1-2
Compound HOMO Orbital LUMO Orbital 1
2
45
3.8 DFT studies on the Nonlinear optical properties of N-(4-Nitrophenyl)naphthalene-1-amine and N-(2,4-dinitrophenyl)naphthalene-1-amine
The simplest polarizability, a, characterizes the ability of an electric field to distort the
electronic distribution of a molecule, that is, the molecule as a whole is perturbed. Consequently,
a change in the equilibrium nuclear geometry will take place as a result of the development of a
different potential-energy surface. The result would be a change in the vibrational and rotational
motions of the molecule. Clearly, an effect of such orientation redistribution cannot be ignored.
Higher order polarizabilities (hyperpolarizabilities β,γ. . .) which describe the non-linear
response of atoms and molecules are related to a wide range of phenomena from non-linear
optics to intermolecular forces, such as the stability of chemical bonds, as well as, the
conformation of molecules and molecular aggregates.
Dipole moment, isotropic polarizability, anisotropic polarizability and hyper polarizability are
calculated using 6-31++ G(d,p) at DFT level using the aforementioned equation and were
enlisted in Table 22.
Table 22. Nonlinear optical properties of N-(4-Nitrophenyl)naphthalene-1-amine and N-(2,4-dinitrophenyl)naphthalene-1-amine
Compound μ ˂α˃ a.u Δα a.u βtot a.u. 1 8.2300 240.43 207.95 2984.187 2 8.3970 263.27 221.64 3436.15
From the table, it is clear that N-(4-Nitrophenyl)naphthalene-1-amine and N-(2,4-dinitrophenyl)naphthalene-1-amine show good nonlinear response
3.9 Characterization Techniques
3.9.a FT-IR
FT-IR spectra were recorded in the transmission mode using KBr pellets on Perkin
Elmer spectrometer operating at 4 cm-1 resolution at a range of 750cm-1 to 4000cm-1.
N-(2,4-dinitrophenyl)naphthalene-1-amine was synthesized and it was confirmed by FT-IR
Spectrum.
46
Figure 4. IR spectrum of N-(2,4-dinitrophenyl)naphthalene-1-amine
IR interpretation
Frequency (cm-1) Assignments 3570-3200
1616
1384
Stretching of hydrogen bonded OH group Stretching of Naphthalene ring NO2 stretching vibration
4500 4000 3500 3000 2500 2000 1500 1000 50015
20
25
30
35
40
Tran
smitt
ance
(%)
wavenumber (cm-1)
47
CHAPTER 4
FINDINGS & CONCLUSIONS
48
4.1 Conclusions
• N-[3-(Naphthalene-1-yloxy)butyl]-4-nitroaniline, N-[3-(Quinoline-4-yloxy)butyl]-4-
nitroaniline, N-[3-(Quinazoline-1-yloxy)butyl]-4-nitroaniline, N-[3-(2,4,5TriazaNaphthalene-
1-yloxy)butyl]-4-nitroaniline, N-[3-(2,4,5,7 TetraazaNaphthalene-1-yloxy)butyl]-4-
nitroaniline were optimized at DFT level. All are showing Cisoid confirmation. Their
HOMO-LUMO is identified. Their nonlinear optical parameters are calculated using 6-31G
(d,p) basis set using B3LYP functional. All the compounds show high nonlinear optical
response. It is further confirmed by using BPV86 and LSDA method.
• N-[3-(Naphthalene-1-yloxy)butyl]-2,4-dinitroaniline, N-[3-(Quinoline-4-yloxy)butyl]- 2,4-
dinitroaniline, N-[3-(Quinazoline-1-yloxy)butyl]- 2,4-dinitroaniline, N-[3-
(2,4,5TriazaNaphthalene-1-yloxy)butyl]- 2,4-dinitroaniline, N-[3-(2,4,5,7
TetraazaNaphthalene-1-yloxy)butyl]- 2,4-dinitroaniline were optimized at DFT level. All are
showing Cisoid confirmation. Their HOMO-LUMO is identified. Their nonlinear optical
parameters are calculated using 6-31G (d,p) basis set using B3LYP functional. All the
compounds show high nonlinear optical response. It is further confirmed by using BPV86
and LSDA method.
• The aforementioned 10 compounds show high β values. It can be attributed to their small
Eg, large delocalization and coplanarity of the naphthalene ring with spacer group. High
delocalization is confirmed by finding effective distance between two rings and planarity of
the ring with spacer is confirmed by identifying the dihedral angle between spacer and
naphthalene ring.
• N-[3-(Quinoline-2-yloxy)butyl]-4-nitroaniline, N-[3-(Quinoline-4-yloxy)butyl]- 4-
nitroaniline, N-[3-(Quinoline-6-yloxy)butyl]- 4-nitroaniline, N-[3-(Quinoline-8-yloxy)butyl]-
4-nitroaniline are optimized at DFT level using B3LYP and 6-31 G(d,p). All compounds
show Cisoid conformation. Their frontier molecular orbitals are found out and Eg are
calculated. All NLO properties are found out and all the compounds show good nonlinear
response.
49
• N-[3-( Quinoline-2-yloxy)butyl]-2,4-dinitroaniline, N-[3-(Quinoline-4-yloxy)butyl]- 2,4-
dinitroaniline, N-[3-( Quinoline-6-yloxy)butyl]- 2,4-dinitroaniline, N-[3-( Quinoline-8-
yloxy)butyl]- 2,4-dinitroaniline are optimized at DFT level using B3LYP and 6-31 G(d,p).
All compounds show Cisoid conformation. Their frontier molecular orbitals are found out
and Eg are calculated. All NLO properties are found out and all the compounds show good
nonlinear response.
• N-[(Naphthalen-5-yl)methyl]-4 nitrobenzamine and N-[(Naphthalen-5-yl)methyl]-2,4
dinitrobenzamine are optimized at DFT level using B3LYP and 6-31++ G(d,p). All
compounds show Cisoid conformation. Their frontier molecular orbitals are found out and
Eg are calculated. All NLO properties are found out and all the compounds show good
nonlinear response.
• DFT studies on the electronic transitions of N-(4-Nitrophenyl)naphthalene-1-amine and N-
(2,4-dinitrophenyl)naphthalene-1-amine are done using B3LYP and 6-31++ G(d,p). All
compounds show Cisoid conformation. Their frontier molecular orbitals are found out and
Eg are calculated. All NLO properties are found out and all the compounds show good
nonlinear response.
• N-(2,4-dinitrophenyl)naphthalene-1-amine is synthesized using 1-naphtylamine and 1-
Fluoro-2,4-dinitrobenzene.Its formation is confirmed by FT-IR.
50
4.2 References
1. R. W. Boyd, “Nonlinear Optics”, Academic Press, INC., 1992, San Diego. Chapter 1.
2. E. G. Sauter, “Nonlinear Optics”, Tohn Wiley, 1996, New York.
3. C. Justin Raj, S. Dinakaran, S. Krishnan, B. Miltonboaz, R. Robert, S. Jerome Das, Opt.
Commun., 281(2008)2285..
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