time resolved structural investigations of soft condensed matter andré rossberg, satoru tsushima

Text optional: Institutsname Prof. Dr. Hans Mustermann www.fzd.de Mitglied der Leibniz-Gemeinschaft André Rossberg | Institute of Radiochemistry | http://www.hzdr.de

Time resolved structural investigations of soft condensed matter

André Rossberg, Satoru Tsushima

Helmholtz Zentrum Dresden-Rossendorf Dresdenand Rossendorf Beamline (ROBL), ESRF, Grenoble

André Rossberg | Institute of Radiochemistry | http://www.hzdr.de

Methods for liquids and amorphous materials

1.Extended fine structure spectroscopy (EXAFS)

For metal complexes in solution, etc. Local atomic environment (interatomic distances,

coordination numbers, type of the atoms, static and

thermal disorder)

2. Wide angle scattering (“PDF method”)

For substrates (nano sized particles, x-ray amorphous)

which may adsorb metal complexes at the surface,

metal complexes in solution, etc. Measuring of all pair distribution functions (PDF or

g(r))


I2 I1 I0

DCM

M1

M2

FL Detector

sampleμ(E) = ln (I0/I1)

= μ0(E) { 1 + (k) }

Q=4π/λ sinθ

2θ

Q(Å

-1)

32

, 2χ exp sin 2 2δ , d

λ

F k r rk kr k k r V

kr kg r

F(Q)

Actinides (L-edges) 16-30 keV

g(r) by shell fit or inverse method1 h for ideal conditionsg(r) only up to 6 Å

Few secondsg(r) direct accessibleFor solutions much higher concentrations necessaryLower resolution in g(r) but up

to high r

E

μ(E

)


Available photons per 10mm2 at ROBL (before reconstruction)

0 5 10 15 20 25 30 35

2.0x1010

4.0x1010

6.0x1010

8.0x1010

1.0x1011

1.2x1011

1.4x1011

Ph

oto

n F

lux

[ph

/s/1

0mm

2 ]

Photon Energy [keV]

Si

Pt

Actinides: 6x1010 photons/s/10mm2

Irradiated area of 10mm2 - typical for EXAFS sample

For reliable EXAFS spectraone may calculate the necessary x-ray shots in dependence on the intended time resolution for time resolved studies…


Time resolved studies

Sampling time of an EXAFS photoelectron is ~0.1 fs

much shorter than the atomic vibrational periods ~0.1 ps !

EXAFS samples a unidimensional distribution of

instantaneous interatomic distances for each coordination shell of

the absorber atom

2( )

4

dNg r

r dr

Dalba, G. & Fornasini, P. (1997). J. Synchrotron Rad. 4, 243-255.


Monitoring structural (EXAFS, PDF) and electronical changes (XANES) for very fast processes like transition states of metal complexes, atomic vibrations

U-O

Ground state

Excited states

1g

0.05 - 0.3 ÅEXAFS: ±0.02 Å

AbsorptionEmission

3g

U-O 1.700 Å

U-O 1.75 Å

3gU-O 2.01 Å, 1.72 Å

spin density of 3g (uf)

1g U-O 1.78 Å3g U-O 1.77 Å1g U-O 1.78 Å3g

U-O 1.99 Å, 1.71 Å

strong hydrogen acceptor

Real et al. J. Chem. Phys. 127, 214302 (2007).Real et al. J. Am. Chem. Soc. 130, 11742, (2008).

Oax U Oax

Structures of the ground state and the lowest-lying triplet states of bare UO2

2+ ion at the CASPT2 level


Photochemical reduction of UO22+

UO22+/H2O/

organic substancesU4+/H2O/byproducts

Complex mechanisms:- methanol

- oxalateQuantum yield (U4+) > 0.5

U(IV), CO2 (weakly acidic) U(VI), CO2, CO (acidic)

Photochemical reaction proceedsvia axial oxygen linkage

S. Kannan et al. JACS, 128, 14024 (2006).

P.L.Arnold et al. Nature Chem. 2, 1056 (2010).P.L.Arnold et al. Angew. Chem.Int.Ed. 50, 887 (2011).A.Yahia et al. Chem. Eur. J. 16,4881, (2010).

Reactivity of uranyl oxygens (2010-)

M.Bühl, G.Schreckenbach, Inorg. Chem. 49, 3821 (2010).Z.Szabó, I.Grenthe, Inorg. Chem., 49, 4928 (2010).

G.Nocton et al. JACS 132, 495, (2010).V.Mougel et al. Chem.Eur.J. 16, 14365 (2010).

S.Fortier & T.W.Hayton Coord.Chem.Rev. 254, 197 ( 2010).J.L.Brown et al. JACS 132, 7248 (2010).


Ground states and lowest-lying triplet states of UO2

2+ linked with methanol and H2OGS

GS

TS

TS

High power UV-Vis pump and TR-EXAFS

Theoretical EXAFS spectra (U LIII edge)

S.Tsushima, Inorg. Chem., 48, 4856 (2009).

2 4 6 8 10 12 14 16

-4

-2

0

2

4

6

8

10

12

14

16

18

20

(k)

*k3

k [Å-1]

0 1 2 3 4

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

FT

R + R [Å]

GS

TS

TS


R.Ghosh, J.A.Mondal, H.N.Ghosh, D.K.Palit, J. Phys. Chem. A 114, 5263 (2010).

Picosecond transient absorption spectroscopyof UO2

2+ nitrate in water and in methanol

water

methanol


It is well-known that uranyl oxalate can decompose under the influence of light. (chemical actinometer)

UO22+ / H2O / oxalate

Brits et al. correlated photodecomposition of uranyl oxalate with UO2(C2O4)2

2- (1:2). However, speciation calculation suggests the prevalence of 1:3 and 2:5 species under the experimental condition of Brits et al..

A. G. Brits, R. Van Eldik and J. A. Van Den Berg, Z. Physik. Chem. Neu Folge, 99, 107 (1976).A. G. Brits, R. Van Eldik and J. A. Van Den Berg, Z. Physik. Chem. Neu Folge, 102, 203 (1976).A. G. Brits, R. Van Eldik and J. A. Van Den Berg, Z. Physik. Chem. Neu Folge, 102, 213 (1976).A.G. Brits, R. Van Eldik and J.A. Van Den Berg, J. Inorg. Nucl. Chem., 39, 1195 (1977).A. G. Brits, R. Van Eldik and J. A. Van Den Berg, Inorg. Chim. Acta, 30, 17 (1978).

Uranyl oxalate 1:3 complex


Uranyl Oxalate 1:3 complex

decarboxylation

S.Tsushima, V.Brendler, K.Fahmy, Dalton Trans., 39, 10953 (2010).

2.40

2.412.41

2.41

2.35

2.46

2.49

2.46 2.50

ground state triplet excited state

2.63

U=O 1.85

(bond distances in Å)

U=O 1.79

CO2

Density functional theory (DFT ) calculations


Inversion of the EXAFS integral equation necessary to get n(r) Fredholm integral equation of the first kind Integral kernel ill conditioned ill posed problem Solution with inverse method For EXAFS Landweber Iteration [1] was tested and is now used [2]

In case of asymmetric g(r) breakdown of the EXAFS shell fit model

32

, 2χ exp sin 2 2δ , d

λ

F k r rk kr k k r g r V

kr k

2 22

1

( , ) 2χ exp exp 2 sin 2 2δ , .

λ

shellsm m m m

m m mm m

N F k r rk k kr k k r

r k k

2.0 2.2 2.4 2.6 2.8 3.0

0.0

0.1

0.2

g(r

)

r [Å]

2

, 2( , ) exp sin 2 2δ ,

λ

F k r rA k r kr k k r

kr k

Integral kernel:

0

χ , d

k k r n rA r

[1] Landweber L. Am. J. Math. Manag. Technol. 1951, 73, 615.

[2] Rossberg, A. & Funke, H. (2010). Journal of Synchrotron Radiation 17, 280-288.

2( )) 4 ( rn g rrCondensed form: , where


• Structural and electronical characterization of excited states of metal complexes• Proof of DFT prediction• study of reaction mechanisms (photochemistry)• One need pump and probe experiment (time: ps to fs)

Summary

Outlook (some other ideas)• Tunable IR Laser, pump and probe experiment single g(r) peaks may change the form due to excitation of vibrational modes = identification of groups, type of atoms,…• Metal complexes (with dipol) in strong electric field (short time) = orientation = 3d structural information by using polarized beam


Acknowledgements

Dr. Harald Funke

Dr. Karim Fahmy

Dr. Vinzenz Brendler

Prof. Dr. Thomas E. Cowan

Zentrum für Informationsdienste und Hochleistungsrechnen, Technische Universität Dresden

Thank you for your attention !!


Potential energy curves of the UO22+ ion as a function of one U–Oyl

bond computed with (a)CCSD and (b) TD-DFT B3LYP. (F.Réal , V.Vallet, C.Marian, U.Wahlgren J. Chem. Phys. 127, 214302 (2007))

DFT is not the best method to study excited states of uranyl(VI).

K.Pierloot, E.van Besien, J. Chem. Phys. 123, 204309 (2005).K.Pierloot, E.van Besien, E. van Lenthe, E. J. Baerends, J.Chem. Phys. 126, 194311 (2007).

CASPT2 vs TD-DFT

Pitfall of DFT


Method and molecular models

H2OMeOH

UO2(H2O)52+

UO2(H2O)52+

Theory: Hybrid DFT (B3LYP) Program: Gaussian 03 　　 Solvent: CPCM Basis sets: ECP on U, O, C and 6-311++G** on H

1. UO22+ / H2O / methanol


Structures of the ground state and the lowest-lying triplet states of bare UO2

2+ ion at the CASPT2 level

U-O

Ground state

Excited states

1g

0.05 - 0.3 ÅEXAFS: ±0.02 Å

AbsorptionEmission

3g

U-O 1.700 Å

U-O 1.75 Å

Real et al. J. Chem. Phys. 127, 214302 (2007).Real et al. J. Am. Chem. Soc. 130, 11742, (2008).

3gU-O 2.01 Å, 1.72 Å

spin density of 3g (uf)

1g U-O 1.78 Å3g U-O 1.77 Å1g U-O 1.78 Å3g

U-O 1.99 Å, 1.71 Å

strong hydrogen acceptor


Spin density of the lowest-lying triplet states of UO2(OH2)5

2+ linked with MeOH and H2O


1.06

0.88

1.96

H2O(no alcohol)

CH3OH(with alcohol)

tripletelectron transfer

U(V) U(VI)


Decar

boxyla

tion

U(VI) U(V)

CO2 gas

Photoreduction


Structure and spin density of the lowest-lying triplet state of UO2(C2O4)3

4-


3. Quenching of uranium(VI) luminescence by ions and molecules

Luminescence(no quenching)

UO2 1.93F 0.07

Invisible luminescence(quenching)

UO2 1.55Cl 0.46

Photoreduction(quenching)

Dissociative(quenching)

UO2 1.05MeOH 0.95

UO2 0.98I 1.00

Geometries and Mulliken spin densities - of the lowest-lying triplet states of UO2

2+ aquo ion associated with F, Cl, I, and methanol.

S.Tsushima, C.Götz, K.Fahmy, Chem.Eur.J.. 16, 8029 (2010).

2.12 eV(585nm)

U-F 2.08Å 3B2

1A1 U-F 2.09Å

0.01 eV

U-I 3.78Å 3B1

1A1 U-I 3.00Å


excitation

decarboxylation

de-excitation

COOH-

1.51Å 2.47Å2.07Å -112kJ/mol

-2kJ/mol

UO22+(aq) UO2

+(aq)

HC2O4-

HO-CO0.

OCOH-

UO22+(aq)

UO22+(aq)

no reduction of U(VI)production of CO and OH-


Alternative mechanism at low pH

Byproducts: U(VI), CO2, CO (acidic) U(IV), CO2 (weakly acidic)

CO2


Why (U4+) > 0.5?

HC

HOH

0 kJ/mol

spin density

UVIO22+(aq)


HCHO formaldehyde

-122 kJ/mol

spin density

UVOOH2+(aq)

Photochemical byproduct can reduce another set of UO2

2+


Dimeric species (2:5)

Solid: J. Leciejewicz, N. W. Alcock, T. J. Kemp, Struct. Bonding, 82, 43 (1995).Acetone: C. Görller-Walrand, K.Servaes, Helv. Chim. Acta, 92, 2304 (2009). Aqueous: J. Havel, J. Soto-Guerrero, P. Lubal,

Polyhedron, 21, 1411, (2002).

or

U-U 6.50Å

EXAFS cannot differentiate 1:3 and 2:5

HEXS


Lowest-lying triplet states

1:1

1:2

1:3 2:5

decarboxylation decarboxylation


2.63

1.85

2.301.83

2.301.83

1.85

1.85

1.85

2.332.40

2.61

(unit in Ångströms)


1:11:2

1:3

V. Vallet, H. Moll, U.Wahlgren, Z.Szabo, I.Grenthe, Inorg. Chem., 42, 1982 (2003).

Uranyl oxalate ground state structures

EXAFS and DFT

time resolved structural investigations of soft condensed matter andré rossberg, satoru tsushima

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