evolution of the mlct band following changes in oxidation state for highly coupled mixed valence...
TRANSCRIPT
Evolution of the MLCT band following changes in oxidation state for highly coupled mixed
valence complexes
Benjamin Lear and Malcolm Chisholm64th International Symposium on Molecular Spectroscopy
June 23rd 2009
Mixed-valence systems and their classification
Localized electronic
states
Non-adiabatic
Adiabatic
Localized electronic
states
Class I
Fre
e E
ner
gy
XDelocalized electronic
states
Class III
Fre
e E
ner
gy
X
Class II
Fre
e E
ner
gy
X
Solvent dependent IVCT band
Solvent independent IVCT band
WW
O
O
O
O
O O
O
O
WW
O
O
O
O
O O
O
O
1+
M M mixed valence complexes
WW
O
O
O
O
O O
O
O
WW
O
O
O
O
O O
O
O WMo
O
O
O
O
O O
O
O
MoW
O
O
O
O
O O
O
OMo
Mo
O
O
O
O
O O
O
O
MoMo
O
O
O
O
O O
O
O
10000 15000 20000 25000
Re
lativ
e I
nte
nsi
ty
Wavenumbers /cm-1
10000 15000 20000 25000
Re
lativ
e I
nte
nsi
ty
Wavenumbers /cm-1
5000 10000 15000 20000
Re
lativ
e In
ten
sity
Wavenumber /cm-1
MLCT in neutral vs. mixed valence state
IVCT band
WW
O
O
O
O
O O
O
O
WW
O
O
O
O
O O
O
O
A three state model for mixed valence chemistry
Asymmetric coordinate
Symmetric
coordinate
Asymmetric
coordinate
Fre
e en
ergy
WW
O
O
O
O
O O
O
O
WW
O
O
O
O
O O
O
O
IVCT MLCT
Electronic transitions of the mixed valence state
10000 15000 20000 25000
Re
lative
In
ten
sity
Wavenumbers /cm-1
MLCTIVCT
WW
O
O
O
O
O O
O
O
WW
O
O
O
O
O O
O
OW
Mo
O
O
O
O
O O
O
O
MoW
O
O
O
O
O O
O
OMo
Mo
O
O
O
O
O O
O
O
MoMo
O
O
O
O
O O
O
O
1+ 1+ 1+
Class III
T1 T3 T2
Frequency
Inte
nsity
Time
Ove
rlap
1/ 1/ 2/
FourierTransform
Nuclear coordinate
Raman spectra
Compound 1
2
3
MM
1 1411 932 576 3952 1351 933 576 3673 1323 915 582 312
Table 4. Energies (in cm-1) of the Raman modes for 1-3 found for excitation resonant with the MLCT transition.
Wavenumber /cm-1
Inte
nsity
MoMo
O
O
O
O
O O
O
O
MoMo
O
O
O
O
O O
O
O
MLCT simulationN
eutr
al
MoMo
O
O
O
O
O O
O
O
MoMo
O
O
O
O
O O
O
OW
Mo
O
O
O
O
O O
O
O
MoW
O
O
O
O
O O
O
OWW
O
O
O
O
O O
O
O
WW
O
O
O
O
O O
O
O
Mix
ed V
alen
ce
12000 15000 18000 21000
0.0
0.5
1.0
nm
Nor
mal
ized
Inte
nsity
Energy /cm-1
1000 900 800 700 600 500
12000 15000 18000 21000 24000
0.0
0.5
1.0
nm
Nor
mal
ized
Inte
nsity
Energy /cm-1
900 800 700 600 500 400
15000 18000 21000
0.0
0.5
1.0
nm
Nor
mal
ized
Inte
nsity
Energy /cm-1
750 700 650 600 550 500
18000 21000 24000 27000
0.0
0.5
1.0
nm
Nor
mal
ized
Inte
nsity
Energy /cm-1
600 550 500 450 400
12000 15000 18000 21000 24000
0.0
0.5
1.0
nm
Nor
mal
ized
Inte
nsity
Energy /cm-1
900 800 700 600 500 400
12000 15000 18000 21000
0.0
0.5
1.0
nm
Nor
mal
ized
Inte
nsity
Energy /cm-1
900 800 700 600 500
18000 21000 24000 27000
0.0
0.5
1.0
nm
Nor
mal
ized
Inte
nsity
Energy /cm-1
600 550 500 450 400
PES offsetsCompound Raman Band Neutral Mixed valence percent reduction
cm-1
Mo4oxa 1411 1.6 0.5 68.75(MoW)2oxa 1351 1.4 0.4 71.43
W4oxa 1323 1.0 0.3 70.00
Nuclear Coordinate
1
1.2x104 1.6x104 2.0x104
0
1x104
2x104
3x104
4x104
5x104
(M
-1cm
-1)
Wavenumbers (cm-1)
1
1+
Mixed valence
Neutral
1.2x104 1.6x104 2.0x104
0
1x104
2x104
3x104
4x104
5x104
(M
-1cm
-1)
Wavenumbers (cm-1)
1
1+
1.2x104 1.6x104 2.0x104
0
1x104
2x104
3x104
4x104
5x104
(M
-1cm
-1)
Wavenumbers (cm-1)
1
1+
Mixed valence
Neutral
O
OO
O
W
W
W
W
1+
O
OO
O
W
W
W
W
1+
Mixed-valence systems and their classification
Localized electronic
states
Non-adiabatic
Adiabatic
Localized electronic
states
Class I
Fre
e E
ner
gy
XDelocalized electronic
states
Class III
Fre
e E
ner
gy
X
Class II
Fre
e E
ner
gy
X
Solvent dependent IVCT band
Solvent independent IVCT band
WW
O
O
O
O
O O
O
O
WW
O
O
O
O
O O
O
O
1+
Symmetric coordinate
PES and classification
Asymmetric coordinate
Asymmetric
coordinateSymmetric
coordinate
Class IClass I Class IIClass II Class IIIClass III Strongly Class IIIStrongly Class IIIClass I Class II Class III Class IV
1.2x104 1.6x104 2.0x104
0
1x104
2x104
3x104
4x104
5x104
(M
-1cm
-1)
Wavenumbers (cm-1)
1
1+
Mixed valence
Neutral
1.2x104 1.6x104 2.0x104
0
1x104
2x104
3x104
4x104
5x104
(M
-1cm
-1)
Wavenumbers (cm-1)
1
1+
1.2x104 1.6x104 2.0x104
0
1x104
2x104
3x104
4x104
5x104
(M
-1cm
-1)
Wavenumbers (cm-1)
1
1+
Mixed valence
Neutral
O
OO
O
W
W
W
W
1+
O
OO
O
W
W
W
W
1+
Conclusions
• MLCT band in mixed valence complexes contains information regarding the underlying states
• Coupling in mixed valence systems tends to make states more similar to one another
1.2x104 1.6x104 2.0x104
0
1x104
2x104
3x104
4x104
5x104
(M
-1cm
-1)
Wavenumbers (cm-1)
1
1+
Mixed valence
Neutral
1.2x104 1.6x104 2.0x104
0
1x104
2x104
3x104
4x104
5x104
(M
-1cm
-1)
Wavenumbers (cm-1)
1
1+
1.2x104 1.6x104 2.0x104
0
1x104
2x104
3x104
4x104
5x104
(M
-1cm
-1)
Wavenumbers (cm-1)
1
1+
Mixed valence
Neutral
O
OO
O
W
W
W
W
1+
O
OO
O
W
W
W
W
1+
Nuclear CoordinateNuclear Coordinate
AcknowledgmentsMalcolm H. ChisholmThe Chisholm research group
Classification of mixed valence complexes: The “nesting” criterion
View along the symmetric coordinate
Class I Class IVClass III
Theories for absorption profiles
Time dependent pictureFranck-Condon picture
Three-state model: Orbital picture
X
g
g
u
u
u
u
MLCT
IVCT
Redox center combinations Bridge orbital
M'
M''
O
O
O
O
O O
O
O
M'
M''
O
O
O
O
O O
O
O
Concerning the current models
X
g
g
u
u
u
u
MLCT
IVCT
Redox center combinations Bridge orbital
M'
M''
O
O
O
O
O O
O
O
M'
M''
O
O
O
O
O O
O
O
Class IV
IVCT
MLCT
“IVCT”
“MLCT”
Class I
Nuclear coordinate Nuclear coordinate
Conclusions
• MLCT band in mixed valence complexes contains information regarding the underlying states
• Coupling in mixed valence systems tends to make states more similar to one another
• Orbital pictures for describing coupling between states are dangerous
1.2x104 1.6x104 2.0x104
0
1x104
2x104
3x104
4x104
5x104
(M
-1cm
-1)
Wavenumbers (cm-1)
1
1+
Mixed valence
Neutral
1.2x104 1.6x104 2.0x104
0
1x104
2x104
3x104
4x104
5x104
(M
-1cm
-1)
Wavenumbers (cm-1)
1
1+
1.2x104 1.6x104 2.0x104
0
1x104
2x104
3x104
4x104
5x104
(M
-1cm
-1)
Wavenumbers (cm-1)
1
1+
Mixed valence
Neutral
O
OO
O
W
W
W
W
1+
O
OO
O
W
W
W
W
1+
Nuclear CoordinateNuclear Coordinate
X
g
g
u
u
u
u
MLCT
IVCT
Redox center combinations Bridge orbital
M'
M''
O
O
O
O
O O
O
O
M'
M''
O
O
O
O
O O
O
O
≠