1 Lecture 3. Applications of x-ray spectroscopy to inorganic chemistry 1. Bioinorganic chemistry/enzymology 2. Organometallic Chemistry 3. Battery materials MetE (cobalamin independent MetSyn) contains Zn Zn is tightly bound Zn is required for activity Is Zn involved in reaction, or does it play a structural role?
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Lecture 3.jphgroup/XAS_Course/Harbin/Lecture3.pdf1 Lecture 3. Applications of x-ray spectroscopy to inorganic chemistry 1. Bioinorganic chemistry/enzymology 2. Organometallic Chemistry
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1
Lecture 3.Applications of x-ray spectroscopy
to inorganic chemistry
1. Bioinorganic chemistry/enzymology
2. Organometallic Chemistry
3. Battery materials
MetE (cobalamin independent MetSyn) contains Zn
Zn is tightly boundZn is required for activityIs Zn involved in reaction, or does it play a
structural role?
2
The Zn site in MetE has ZnS2(O/N)2
ligation.
-4
0
4
8
2 4 6 8 10 12
EX
AF
S•k
3
k (Å-1)
0
5
10
15
20
0 1 2 3 4 5 6 7Fou
rier
Tra
nsfo
rm M
agni
tude
R + (Å)
Native+Hcy
Addition of homocysteine changes ligation to ZnS3(O/N).
Changes in ligation are due to homocysteine binding to Zn
0
10
20
30
40
50
60
0 1 2 3 4 5 6 7
Fou
rier
Tra
nsfo
rm M
agni
tude
R + (Å)
Native
+SeHcy+Hcy
MetH (ZnS3O)
MetE (ZnS2NO)
3
Combination of Zn + Se EXAFS consistent with only a small distortion from tetrahedral
geometry in substrate-bound enzyme
J. Am. Chem. Soc., 112 (10) 1990p. 4031-4032
p. 4032-4034
4
EXAFS shows that CN–
does not remain bound
0 1.5 3 4.5 6 7.5
Four
ier
Tra
nsfo
rmM
agni
tude
R + (Å)
CuCN•2LiCl
Cu-Nearest Neighbor
Cu-CNCu-CN-Cu
CuCN•2LiCl + MeLi
CuCN•2LiCl + 2 MeLi
Structures of cyanocuprates in THF
Cu C NN
CCu
Cu
Cl
MeLi
MeLi
Cu C NMe
Cu MeMe
C NLi Li
5
Solution speciation of CuI+PhLiPhLi + CuI “phenylcopper”
2PhLi+ CuI “diphenylcuprate”
1:1 Cu4Ph4(Me2S)2
Cu5Mes5
1.2:1 [Cu5Ph6]–
1.5:1 [Cu4LiPh6]–
[Cu4MgPh6]
2:1 [CuPh2]–
[CuPh2Li]2
[Cu3Li2Ph6]–
Crystalline phenyl:copper species
0
50
100
150
200
250
300
8970 8980 8990 9000 9010 9020
Nor
mal
ized
Abs
orba
nce
Energy ( eV )
n=0.0
n=0.2
n=0.4
n=0.6
n=0.8
n=1.0
n=1.1
n=1.2
Titration of CuI+ n PhLi shows isosbestic behavior up to 1.2 equivalents
6
Titration of CuI+ n PhLi shows isosbestic behavior from 1.2-2.0 equivalents
0
50
100
150
200
250
300
8970 8980 8990 9000 9010 9020
Nor
mal
ized
Abs
orba
nce
Energy ( eV )
n=2.0n=1.8
n=1.7n=1.5n=1.4n=1.3n=1.2
EXAFS data support XANES speciation
[Cu5Ph6]–
[CuI2]–
[CuPh2]–
0 0.5 1 1.5 20
0.2
0.4
0.6
0.8
1
PhLi / CuI Ratio
Cu
Com
posi
tion
1.2
CuI2-
Cu5Ph6-
CuPh2-
7
In-situ X-ray Absorption Spectroscopy
Aniruddha Deb et al. J. Synchrotron Rad. (2004). 11, 497–504
In-situ X-ray Absorption Spectroscopy
8
Charge/Discharge at 0.1C
Li3V1.9Mg0.15(PO4)3
- Cut off : 3.0 V-4.5V
- Charge: 121 mAh/g- Discharge: 104
mAh/g
Li3V1.9Mg0.15(PO4)3
- Cut off : 3.0 V-4.8V
- Charge: 136 mAh/g- Discharge: 100
mAh/g
Li3V1.9Mg0.15(PO4)3
Energy(eV)
5460 5480 5500 5520
No
rmal
ized
In
ten
sity
0
200
400
600
800
5464 5468 54720
20
40
60
Charge: 3.0-4.5V
Energy(eV)
5460 5480 5500 5520
No
r,m
ali
zed
In
ten
sity
0
200
400
600
800
5464 5468 54720
20
40
60
Discharge: 3.0-4.5V
Between 3.0-4.5V No change shown in the pre-edge region for a cut off of 4.5V Between 3-4.5V changes in the edge, observed, showing oxidation
state change No significant eg-t2g splitting observed in the pre-edge region Octahedral structure preserved
9
Energy (eV)
5460 5480 5500 5520
No
rma
lize
d I
nte
ns
ity
0
200
400
600
800
2D Graph 1
5464 5468 5472 54760
50
100
150
200
Discharge 2.0-4.8V
Energy (eV)
5460 5480 5500 5520
No
rma
lize
d I
nte
ns
ity
0
200
400
600
800
5464 5468 5472 54760
50
100
150
200
Charge:3.0-4.8V
Li3V1.9Mg0.15(PO4)3
Above 4.5V and below 3.0V Above 4.5V change in edge consistent with formation of tetrahedral
V4+ or V5+. XANES change is largely irreversible. Possible structural change below 3.0V as the