Pulsed Field Ionization-Zero Electron Kinetic Energy (PFI-ZEKE) Spectroscopy of

Sc-C6H5X(X=F,CH3,OH) Complexes

Changhua Zhang, Serge A. Krasnokutskia and Dong-Sheng Yang

Department of Chemistry, University of Kentucky

06-19-2008

Motivation• Metal aromatic complexes are of fundamental importance in organometall

ic chemistry and relevant to chemical catalysis and biological processes. • These complexes are prototype models for general understanding of meta

l interactions with aromatic molecules.

• Adiabatic ionization energy

• Vibrational structures

• Electronic states

• Metal binding site and strength

• Substituent effect

Sc-C6H6

(4A1,C6v)

B. R. Sohnlein, S. Li, and D.-S. Yang,

J. Chem. Phys. 123, 214306 (2005)

PFI-ZEKE Photoelectron Spectroscopy Set-up

Calculations:DFT (B3LYP/6-311+G**) and Franck-Condon (FC) factor calculations

Pulsed Valve and M eta l Rod

HV

M CP

TP 400L/s

TP 400L/sDP 2300L/s

Carrier G as

Extraction Cans

T ime of F light Tube

M etal

L iqu id/Solid GateValve

Skimmer

PIE Spectra of Sc-C6H5X Complexes

Wavenumber / cm-141000 41500 43000

Sc-C6H5OH

Sc-C6H5CH3Sc-C6H5F

Ionization energies: Sc-C6H5CH3< Sc-C6H5OH < Sc-C6H5F

PFI-ZEKE spectrum of Sc-C6H5F in He.

Wavenumber/ cm-1

42800 43000 43200 43400 43600 43800 44000 44200 44400

374

IE=42985cm-1

43000 43200 43400 43600 43800 44000 44200

Wavenumber / cm-1

374

(a) Experiment

(b) 1A<--2A

40 348

552

Experimental ZEKE spectrum and simulations from1A←2A transition at 200 K.

Sc-C6H5F

(Top view)

(Side view)

Enantiomers 2A C1

Sc-C6H5CH3

41200 41400 41600 41800 42000 42200 42400 42600

Wavenumber /cm-1

378

PFI-ZEKE spectrum of Sc-C6H5CH3 in Ar

41000 41200 41400 41600 41800 42000 42200 42400 42600

Wavenumber /cm-1

378134

476

Experimental ZEKE spectrum and simulations from1A←2A transition at 10 K.

(Top view)

(Side view)

Enantiomers 2A C1

Sc-C6H5OH

41200 41400 41600 41800 42000 42200 42400

140

Wavenumber / cm-1

380

38080

* *

PFI-ZEKE spectrum of Sc-C6H5OH in Ar

(Top view)

(Side view)

+ 0.3 kJ/mol

s-cis s-trans

-100 -50 0 50 100 150 200 250 300

0

5

10

15

20

dihedral angle of H-O-C-C (degree)

PES of Sc-C6H

5OH

Re

lativ

e e

lect

ron

ic e

ne

rgie

s (k

J/m

ol)

-100 -50 0 50 100

0

1

2

3

4

5

6

7

Rel

ativ

e e

lect

ron

ic e

nerg

ies

(kJ/

mol

)

dihedral angle of H-C-C-C (degree)

PES of Sc-C6H

5CH

3

AIEs (cm-1), bond dissociation energies (D0+(D0)) (kJ/mol), and vibrational frequencies (cm-1)

ZEKE B3LYP

Sc-C6H5F AIE 42985 42988

D0+(D0) 188.6(69.6)

Out of plane ring distortion ν21+ 552 559

Sc-C6H5F stretch ν24+ 374 378

Out of plane ring bending ν25+ 348 351

F-C bending ν28+/ν28 ν28

+-ν28=42 ν28+-ν28=17

Sc-C6H5CH3 AIE 41167 40802

D0+(D0) 224.5(79.4)

Out of plane ring distortion ν35+ 476 495

Sc-C6H5CH3 stretch ν36+ 378 378

Out of plane ring bending ν37+ 344 349

CH3 rock ν42+ 134 144

Sc-C6H5OH AIE 41477/41557 41138/41178

D0+(D0) 217.0(75.9)/216.2(75.6)

Out of plane ring distortion ν28+ /570 /580

Sc-C6H5OH stretch ν32+ 380/380 379/379

Out of plane ring bending ν36+ /140 /120

Conclusions

• For the first time, Sc-C6H5X(X=F,CH3,OH) complexes have been studied by ZEKE spectroscopy.

• Ionization energies: Sc-C6H5CH3< Sc-C6H5OH < Sc-C6H5F.

• Sc-C6H6 is in C6v point group with triplet ionic state and quartet neutral state. Sc-C6H5X are in π configuration with 1A and 2A as the cationic and neutral ground electronic states, respectively.

• The benzene ring in Sc-C6H6 keeps flat.The aromatic rings in Sc-C6H5X show distortion structures that two carbons in each ring displaced toward the metal atom.

• All complexes have enantiomers. Cis-trans isomers of Sc-C6H5OH are obtained by ZEKE.

Thank you!