quantum chemical study of raman spectroscopy of substituted benzene derivatives adsorbed on metal...
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Quantum Chemical Study of Raman Spectroscopy of Substituted Benzene Derivatives Adsorbed on
Metal Surfaces
De-Yin Wu, Zhong-Qun Tian
Department of Chemistry in College of Chemistry and Chemical Engineering & State Key Laboratory of Physical Chemistr
y for Solid Surfaces
Xiamen University
Ohio, 2010.6.24
Studies on solution/metal electrodes
High detection sensitivityHigh detection sensitivity
High ResolutionHigh Resolution
EnergyEnergy
SpaceSpace
TimeTime
2-20 Å
Surface-enhanced Raman spectroscopy ： SERS
Surface plasmon resonance
Chemical property
Our Research Pathway：1. Assignment of vibrational Raman bands.
2. To find the insight of vibrational frequency shift.
3. To understand the change of Raman intensity
To determine the dependence between structures and molecular spectra, to infer structures and reaction of adsorbed molecules on metal surfaces.
C
C
C
C
C
N
H
H
H
H H
M
M
M M MM
MMM
Y
Z
H H
HH
H H
N
H H
H
H H
1 1
Molecules/Metallic cluster model
C1
C6
C5
C4
C3
C2
X2
X1
SH
SH
SH
NH2
NH2
NH2
NH2 SH
AN TP
BDA
DSB
pMA
x1, x2= -NH2x2= -SH
x1, x2= -SHx1 = -NH2
BDT
Adsorption models of different molecules
Computational details
Cluster Model: Mn – Molecule – Mn (M = Au, Ag; n =2,3, 4…13)
DFT: B3LYP, PW91PW91, …
Basis set: LANL2DZ (Ag)/ Optimized structure
6-311+G(d,p)(C,N,H,S) Bonding analysis
Scaled Quantum Mechanics force field method (SQMF)]
Calculations of Raman Intensity ：
4
2 202
45 78 45 1 exp
R ii i i
i i B
v vhI
cv hcv k T
Non-resonance, pre-resonance, and resonance cases
0.00
0.04
0.08
Aniline
0.00
0.08
0.16
BDT
0.00
0.08
0.16R
aman
Inte
nsity
Benzene
400 600 800 1000 1200 1400 1600 1800
0.00
0.04
0.08
Thiophenol
400 600 800 1000 1200 1400 1600 1800
0.00
0.04
0.08
pMA
0.00
0.08
0.16
Raman Shift/cm-1
BDA
(1)Simulated Raman spectra of Benzene Derivatives
H
H
H
H
H
H
SH
H
H
H
H
H
NH2
H
H
H
H
H
SH
SH
H
H
H
H
NH2
NH2
H
H
H
H
SH
NH2
H
H
H
H
Vibrational coupling existing
（ 2 ） Thiophenol (TP) and Benzenedithiol (BDT)/Au SERS
0.00
0.25
0.50
Raman Shift/cm-1
TP-Au5
Ram
an
In
ten
sity
(X1
0-3
0 cm
2 /mo
l)
400 600 800 1000 1200 1400 1600 1800
0.00
0.50
1.00TP-Au
13
J. H. Tian, et al., JACS, 2006,128,14748.
Bridge site
Hollow site
Au5-BDT-Au5
SH
H
H
H
H
H
Not sensitive to adsorption site
SH
SH
H
H
H
H
Thiol
(3) Aniline and Benzenediamine (BDA)/Au SERS
400 600 800 1000 1200 1400 1600 1800
0.0
0.2
0.4 AN-Au2
Ram
an In
tensi
ty
Raman Shift/cm-1
0.0
0.2
0.4 AN-Au4
0.0
1.0
2.0
BDA-Au2
0.0
1.0
2.0
3.0
Au2-BDA-Au2
400 600 800 1000 1200 1400 1600 1800
0.0
1.0
2.0
Ram
an Int
ensi
ty(X
10-3
0 c
m2/m
ol)
Raman Shift
BDA-Au4
400 600 800 1000 1200 1400 1600 1800
0.0
1.0
2.0
3.0
Au4-BDA-Au4
400 600 800 1000 1200 1400 1600 1800
0.0
1.0
2.0
Au4-cis-BDA-Au4R
am
an Inte
nsi
ty(X
10-30 c
m2 /m
ol)
Raman Shift/cm-1
Amino
NH2
H
H
H
H
H
NH2
NH2
H
H
H
H
(4) Questions in SERS of PATP/Ag
Osawa M., et al. J. Phys. Chem. 1994, 98, 12702.
Abnormal: 1142, 1391, 1440 cm-1
CT mechanism on b2 modes of PATP
Is it a real story?
PATP/Ag
PATP solid
Weak
Strong
HS- -NH2
1142
13911440
B3LYP/6-311+G**(C,N,S,H)/
Lanl2DZ(Ag)
PATP binding to different sites, such as top, bridge, hollow, and bi-end configurations
（ 4 ） Simulated Raman Spectra of PATP/Ag
Fingerprint region:
（ 1 ） Weak in intensity
（ 2 ） No fundamental band
Hollow site
(4) Simulated Raman spectra of PATP/Au
400 600 800 1000 1200 1400 1600 1800
01020
Au3-PATP-Au
2
0.01.02.0
Ram
an In
tens
ity (X
10-3
0 c
m2 /m
ol) Au
5-PATP
0.01.02.0 Au
5-PATP
0.01.02.0 Au
5-PATP
0.01.02.0
Raman Shift /cm-1
Au5-PATP-Au
6
(4) Beyond supposed mechanisms for PATP?
& ?
(1) Charge Transfer
（ HT vibronic term ）N. Matsuda, et al., Chem. Lett. 1992,7,1385
M. Osawa, et al., J. Phys. Chem. 1994, 98, 12702
(2) Isomerization of
Aromatic and Quinonoidic
W. Hill, B. Wehling, J. Phys. Chem., 1993, 97, 9451
(3) Charge tunneling in metal/PATP/metal nanogap
Au/-SC6H4NH2+
/Ag
Q. Zhou, et al. Angew. Chem. 2006, 45, 397
1064 nm514.5 nm
790 nm
790 nm
SERS
Solid
Acidic
aromatic
Alkaline quinonoidic
Theoretical Study
(4) A new mechanism: 2 * PATP/M DMAB/M
N
N SH
HS
N
N SH
HS
NH2
H2N SH
HS
H
H
2H+
2H+
a. Electrochemical anodic oxidation of aniline;
Y. Matsuda, et al. Bull Chem. Jap., 1971, 44, 2960-2963.
b. Optically catalytic Oxidation (hv/Alkaline/silver; hv/Ag+/TiO2)
H. Park, et al., J. Phys. Chem., 1990, 94, 7576. (P-aminobenzoic acid/Silver Electrode)
DMAB reversibly decomposesDMAB yields
DMAB: p,p´-dimercaptoazobenzene
(4) Ag5/DMAB and Ag5/DMAB/Ag5
B3LYP PW91PW91
Free Molecule
Singe-end
Double-end vC-N C-H
vN=N
Ag
600 800 1000 1200 1400 1600 1800
0
2
4
6
8
10
12
Raman shift(cm-1)
Inte
nsi
ty
PW91PW91
600 800 1000 1200 1400 1600 1800
0
2
4
6
8
10
12
B3LYP
600 800 1000 1200 1400 1600 1800
0
2
4
6
8
10
12
PBE1PBE
600 800 1000 1200 1400 1600 1800
0
2
4
6
8
10
12
B3PW91
600 800 1000 1200 1400 1600 1800
0
2
4
6
8
10
12
MPW1PW91
600 800 1000 1200 1400 1600 1800
0
2
4
6
8
10
12
B3P86
600 800 1000 1200 1400 1600 1800
0
2
4
6
8
10
12
BP86
(4) Simulated Raman spectra of azobenzene
(4) Comparison of Structural parameters
We find B3LYP overestimates the N=N bond, resulting in the blue shift of the vN=N stretching frequency; PW91PW91 and BP86 are more reliable to describe the N=N bond.
1000 1200 1400 1600 1800Raman Shift(cm-1)
S
NH2
Ag
S
NH2
Ag
S
NH
Au
Ag
S
N
Ag
N
SH
Ag
+ e-
hv
? ? ?!!!
+ e-
+
-
The nature of SERS?Surface catalytic coupling reaction
JPCC2009,113,18212
× × ×JPCC2009,113,18212
×
1000 2000 3000Raman Shift /cm-1
900 1200 1500Raman Shift /cm-1
NH2HS
N NHS SH
SERS of DMAB and pATP on Ag NPs
Prof. Hongping Zhu JACS2010,132,9244
NH2HS N NHS SH
Direct evidence
4. Conclusion
(1) The amino group is more chemical activity than the thiol grou
p on coinage metal surfaces.
(2) PATP may undergo surface catalytic coupling reaction to for
m azobenzene derivative, yielding the intense Raman bands a
t 1140, 1390, and 1440 cm-1 。
(3) PW91PW91 and BP86 is better to describe the N=N double b
ond than B3LYP.
(4) Quantum chemical calculation is helpful to understand the ob
served phenomenon in the view of nature.
Acknowledgement ：
Collaborators:
Prof. Bin Ren (Xiamen University)
Prof. Xin Xu (Fudan University)
Prof. S. H. Lin (IAMS, Taipei)
Prof. Yi-Jin Yan (HKUST, Hong Kong)
Doctoral and Master students ：Xiu-Min Liu, Yi-Fan Huang ， Liu-Bin Zhao ， Rong Huang ， Wen-Li Luo
Fund:
Chinese NSF, 973 (2007CB815303, 2009CB930703)
Thanks for your attention!
Thanks for your attention!
(4) pH effect: Reversibility of Raman spectra of PATP
W. Hill, B. Wheling, J. Phys. Chem., 1993, 97, 9451
Na2S2
pH = 2.0
Acidic
Alkaline
Acidic ---good
Basic ----bad
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