ground state electronic structures from multi-edge analysis
TRANSCRIPT
Ground State Electronic Structures
from
Multi-Edge Analysis
Robert K. Szilagyi Montana State University, Bozeman, MT
computational.chemistry.montana.edu
Reminders: unique research opportunities
(no other spectroscopic technique for S and Cl)
facilities
(beamlines, instrumentation, sample prep. expertise)
semi-empirical theory
(effective nuclear charge, transition dipole, covalency
Nitrosated
β-subunit of human hemoglobin
N.-L.CHAN,P.H.ROGERS,A.ARNONE 1.9 Å CRYSTAL STRUCTURE OF THE S-NITROSO FORM OF LIGANDED HUMAN HEMOGLOBINBIOCHEMISTRY, 1998, 37, 16459
βCys93
RSNO compounds: electronic structure
S-N double (π) bond
S-N single (σ) bond
S-C single (σ) bond
large sulfurcontribution
Biochemical and Biophysical Research Communications, 2005, 330(1), 60-64
S K-edge XAS of S-nitrosated glutathione (GSNO)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
2460 2465 2470 2475 2480 2485calibrated (thiosulfate) photon energy, eV
norm
aliz
ed X
AS
inte
nsity
(FF/
I0)
Biochemical and Biophysical Research Communications, 2005, 330(1), 60-64
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
2467 2469 2471 2473 2475 2477 2479calibrated (thiosulfate) photon energy, eV
norm
aliz
ed X
AS
inte
nsity
(FF/
I0)
S K-edge XAS of S-nitrosated glutathione (GSNO)
ON-S σ*S-C σ*
ON-S π*
2471.5 eV
2473.4 eV
2475.0 eV
(0.0 eV)
(2.1 eV)
(4.0 eV)
S K-edge XAS of SNO compounds
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2467 2469 2471 2473 2475 2477 2479 2481
Photon Energy, eV
Nor
mal
ized
XA
S In
tens
ity
GSNO
SNAP
S-nitroso glutathione
N-acetyloxy-3-nitrosothiovaline
S-NOπ*
S-NOσ* S-C
σ*
S K-edge XAS of S compounds
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2467 2469 2471 2473 2475 2477 2479 2481
Photon Energy, eV
Nor
mal
ized
XA
S In
tens
ity
S-C σ*
H-S σ*
S-C σ* NaSEt
Cys
Na+
-S-CH2
-CH3
H-S-CH2
-CH3
S charge becomes less negativeZeff (S) increases
S K-edge XAS of S compounds
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2467 2469 2471 2473 2475 2477 2479 2481
Photon Energy, eV
Nor
mal
ized
XA
S In
tens
ity
ON-S π*
ON-S σ*
S-C σ*
H-S σ*
S-C σ*
Cys
GSNO
H-S-CH2
-R
S charge becomes less negativeZeff (S) increases
ON-S-CH2
-R
ON+ -S-CH2
-R
S K-edge XAS of S compounds
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2467 2469 2471 2473 2475 2477 2479 2481
Photon Energy, eV
Nor
mal
ized
XA
S In
tens
ity
ON-S π*
ON-S σ*
S-C σ*S-C σ*
H-S σ*
S-C σ* NaSEt
Cys
GSNO
S charge becomes less negativeZeff (S) increases
S K-edge XAS as detection method for SNO
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477
Photon Energy, eV
Nor
mal
ized
XA
S In
tens
ity
-3.5
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0D
erivatives of XA
S IntensitySNO-hemoglobin
ON-S p* fit
First derivative
Second derivative
S 1s→ ON-S π* fit
Biochemical and Biophysical Research Communications, 2005, 330(1), 60-64
Multi-edge XAS
Conceptually NOT an original idea!
Conscious exploitation of complementary ground state electronicstructure information from multiple absorbers
Molecular Orbital Theory:
Experimentally probing the excitation of an absorber core electron (1s for K) to a unoccupied/virtual molecular orbital with some absorber contribution.
Donor orbital: S 1s (localized on S, in MO picture as s.a.l.c.)
Acceptor orbital: ϕ* = Σ
ci
φi
for a ‘simple’
M-S
bond: ϕ* = cM,d
φM
(nd) + cM,s
φM
(n+1 s) + cM,p
φM
(n+1 p)
cS,s
φS
(3s) + cS,p
φS
(3p) + cS,d
φS
(3d)
Multi-edge XASfor a ‘simple’
M-S bond:
ϕ* = cM,d
φM
(nd) + cM,s
φM
(n+1 s) + cM,p
φM
(n+1 p) cS,s
φS
(3s) + cS,p
φS
(3p) + cS,d
φS
(3d)
metal contribution/character ligand character/covalency
for intense spectral features in absorption spectroscopy –
Δl = 1
M 2p M 1s L 2pL 1s
metal L-edge XAS metal K-edge XAS ligand K-edge L-edge
SSRL BL10-1/8-2 BL7-3/9-3/4-1/4-3 BL6-2/4-3 BL10-1/8-2
SSRL BL10-1 SSRL BL7-3 SSRL BL4-3
2000eV 3000eV 4000eV 5000eV
2146eVP
2472eVS
2822eVCl
3206eVAr
3608eVK
4038eVCa
4492eVSc
4966eVTi
5465eVV
K edgesexcitationform n=1orbital
L edgesexcitationsform n=2orbitals
2007eVSr
2156eVY
2307eVZr
2465eVNb
2625eVMo
2793eVTc
2967eVRu
3146eVRh
3330eVPd
2000eV 3000eV
M edgesexcitationsform n=3orbitals
2365eVHf
2469eVTa
2575eVW
2682eVRe
2792eVOs
2909eVIr
3027eVPt
2300eV 3000eV
Multi-edge XAS at SSRL BL6-2/4-3
Pd
Cl
Cl
PP
LUMO
Multi-edge XAS: A non-biological, but simple example
Inorganica Chimica Acta, 2008, 361(4), 1047-1058
Phosphorous 3p character of the palladium-phosphorous bonds is determined from phosphorous K-edge XAS
Multi-edge XAS: phosphorous K-edge
Chlorine 3p character of the palladium-chlorine bonds is determined from chlorine K-edge XAS
Multi-edge XAS: chlorine K-edge
Metal 4d character of the palladium-ligand bonds is determined from palladium L-edge XAS (only LIII
edge is shown)
Multi-edge XAS: palladium L-edge
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
2815 2817 2819 2821 2823 2825 2827 2829 2831 2833 2835Photon Energy, eV
Nor
mal
ized
XA
S In
tens
ity
Cs2ZnCl4
Cs2CuCl4
NaCl
D4h
Td
Cl 1s
Cl 3psalc
Cu 3dx2-y2
ϕ*
= Cu 3dx2-y2
_ α
Cl 3psalc)1( 2α−
Chlorine K-edge XANES: Cu(II) is the hydrogen atomof inorganic chemistry
(Solomon)
Multi-edge XANES: Cl Pd(II) is the hydrogen atomof organometallic chemistry
Inorganica Chimica Acta, 2008, 361(4), 1047-1058
2
d,lligands ligands orbitals
o,lo,ld,ld,lligands
Md,l2 ||cc||c)1(I
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛>φφ<α−>φφ<α−∝ ∑ ∑ ∑∑ rr
Experimental M-L covalency
LM2
a )1( φα−φα−=Ψacceptor orbital ∑ ∑ φ=φligands orbitals
o,lo,lL c
d,lligands
d,ld c φ=Ψ ∑donor orbital (donor is 1s for K-edge excitations)
electric dipole allowed transition/Fermi golden rule: 2da ||I >ΨΨ<∝ r
ligand core/metal overlap ≈
0 ligand core/ligand core overlap ≈
0
>ΨΨ<α−>ΨΨ< ∑ )(Rad||)(Rad31cc|| s1,lnp,l
ligandsnp,ls1,lda rrfor 1s → np excitation
< R
> dipole integral
><α=>ΨΨ<= − R22)s1(L)p3(LM 3
1||I r
JACS, 1992, 112(4), 1643-1645
Multi-edge XANES: chloropalladium(II/IV)
using I(Cl-t ) = 21.0 eV → ~50% Cl covalency in both [PdIICl4 ]2-
and [PdIVCl6 ]2-
from complementarity this corresponds to ~50% Pd covalency ineach molecular orbital probed by XAS
from area under pre-edge features at Pd L-edges we get I(PdII) = 20.8 (SSRL) 16.9 (ALS) eVI(PdIV) = 14.1 (SSRL) 11.9 (ALS) eV
to test the transferability we used I(PdII) to determine the covalency of Pd-Cl bonds in PdCl2 to be ~50% with a new transition dipole integral for I(Cl-b )16.4 (SSRL) 14.5 (ALS)
Pd-Cl bond in organometallic chemistry is the
Fe-S bond in coordination chemistry
Multi-edge XANES: non-innocent ligands
C
A) Crystal structure of [Ph2
BPtBu2
]CuII(NTol2
)B) Structural overlay of reduced and oxidized formsC) Ligand based redox chemistry
2+
-
-
JACS, 2009, 131(11), 3878-3881
Multi-edge XANES: non-innocent ligands
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
8967 8974 8981 8988 8995 9002Photon Energy, eV
Nor
mal
ized
Inte
nsity 8984.5 eV
8982.5 eV8982.2 eV
first electric dipole allowed Cu 1s → 4p transition
8987.4 eVCu K-edge
CuICl
anhydrous CuIICl2
{[Ph2BPtBu2]CuI(NTol2)}
{[Ph2BPtBu2]CuII(NTol2)}
Multi-edge XANES: non-innocent ligands
0.0
0.5
1.0
1.5
2.0
2.5
3.0
2140 2142 2144 2146 2148 2150Photon Energy, eV
Nor
mal
ized
Inte
nsity
2145.3 eV
P 1s → P-C σ* P 1s → P 4p
2146.5 eV2146.5 eV
2147.9 eV2147.9 eV
P 1s → P 3p/4p basedelectric dipole allowedtransitions
P K-edge
PPh3
{[Ph2BPtBu2]CuI(NTol2)}
{[Ph2BPtBu2]CuII(NTol2)}
2171.1 eV
Multi-edge XANES: non-innocent ligands
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
922 925 928 931 934 937 940Photon Energy, eV
Nor
mal
ized
inte
nsity
Cu 2p → 3d transition
*
931.9 eV
*
930.4 eV
Cu → L backdonation
transition envelopes
Cu LIII-edge
CuICl
anhydrous CuIICl2
{[Ph2BPtBu2]CuI(NTol2)}
{[Ph2BPtBu2]CuII(NTol2)}
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
922 925 928 931 934 937 940Photon Energy, eV
Nor
mal
ized
inte
nsity
931.9 eV
930.4 eV Cu LIII-edge
anhydrous CuIICl2
{[Ph2BPtBu2]CuII(NTol2)}
Multi-edge XANES: quantitative treatment
What is the Cu contribution to the redox active orbital?
What is the % Cu characterthe blue vs. green areascorrespond to?
Multi-edge XANES: quantitative treatment
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2720 2770 2820 2870 2920 2970 3020Photon Energy, eV
Ren
orm
aliz
ed In
tens
ity
Cs2CuIICl4
anhydrous CuIICl2
Cl K-edge
4 Cl absorbers
2 Cl absorbers
Multi-edge XANES: quantitative treatment
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2815 2818 2821 2824 2827 2830Photon Energy, eV
Ren
orm
aliz
ed X
AS
Inte
nsity
D2d Cs2CuCl4pre-edgearea = 0.521 eV~ 30% Cl 3p
anhydrous CuCl2 pre-edge area = 0.616 eV~ 35% Cl 3p
Cs2CuIICl4anhydrous CuIICl2
Cl K-edge
4 Cl absorbers
2 Cl absorbers
Multi-edge XANES: quantitative treatment
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
922 925 928 931 934 937 940Photon Energy, eV
Nor
mal
ized
inte
nsity
931.9 eV
930.4 eV Cu LIII-edge
anhydrous CuIICl2
{[Ph2BPtBu2]CuII(NTol2)}
35% Cl 3p characterwith limited 4s mixingCu 3d character is ~ 65%pre-edge area = 4.114 eV
pre-edge area 0.910 eVCu 3d character ~14%
Calculated spin densities for [Ph2
BPtBu2
]CuII(NTol2
)
(p-tol)2
: 20%
BPh2
: 2%
PtBuPh2
: 15%
N: 49%
Cu: 13%
JACS, 2009, 131(11), 3878-3881
galactose oxidase
1GOGfungus Dactylium dendroides
OOH
CH2
OH
OH
OH OH
OOH
CH
OH
OH OH
O
+ O2
+ H2
O2
State-of-the-Art S K-edge Data
galactose oxidase
His581
His496
Tyr495
Tyr272Cu
water
Cu2+/•O(Tyr-Cys)
Cu2+/O(Tyr-Cys)
Cu+/O(Tyr-Cys)
400 mV
150 mV
Cys228
State-of-the-Art S K-edge Data
galactose oxidase
His581
His496
Tyr495
Tyr272Cu
water
Cys228
State-of-the-Art S K-edge Data GO samples:93% Cu-loaded
150 μL0.633 mM
In phosphate buffer
w/2M urea, pH=750-fold excess of
K3 Fe(CN)637±3% oxidation
BL6-2 only!LHe cryojet only!
19 absorbers:13 Met 4 Cys-Cysthioether crosslink
JACS, 2010, submitted
State-of-the-Art S K-edge Data
0.0
0.5
1.0
1.5
2.0
2.5
3.0
2465 2467 2469 2471 2473 2475 2477 2479
Photon Energy, eV
Nor
mal
ized
XA
S In
tens
ity ferricyanide oxidized
as isolated/semi reduced
dithionite reduced* buffer
contaminationTyrCys1-
(Met13Cys5)
TyrCys1-
(Met13Cys5)
His581
His496
Tyr495
Tyr272Cu
water
Cys228
State-of-the-Art S K-edge Data
0.0
0.5
1.0
1.5
2.0
2.5
3.0
2465 2467 2469 2471 2473 2475 2477 2479
Photon Energy, eV
Nor
mal
ized
XA
S In
tens
ity ferricyanide oxidized
as isolated/semi reduced
dithionite reduced
presence of Tyr-Cys• in Met13Cys5 background
TyrCys1-
(Met13Cys5)
TyrCys1-
(Met13Cys5)
oxidized-reducedXANES spectrum
renormalized pre-edgehhlw = 0.40 eV
A = 0.78thus D0 = 0.31
* buffer contamination
State-of-the-Art S K-edge Data
Experimental area D0
= 0.016 eV for Nabs
= 19 and nholes
= 1.
S character (α2) is defined by the transition dipole expression
3p) 1s I(S 3p) (SN
n 31D 2
absorber
holes0 →= α
I(S 1s→3p) for sulfide
(formally Z=-2)
6.54 eV
for thiolate (formally Z=-1)
8.47 eV
for thioether
(formally Z=0)
10.4 eV
and with corrections for partial Cu loading and Tyr-Cys oxidation:
S character (α2) from XAS for oxidized holo GO is 24±11% (calc.: 22±2%)
from EPR for oxidized apo GO is 20±3% (calc: 15±1%)JACS, 2010, submitted