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Title: Electroscopy Ionization Photoelectron Spectroscopy: Probing the Electronic Structure of Inorganic Metal Complexes in the Gas Phase

Abstract

The coupling of electrospray to photoelectron spectroscopy has allowed a number of negatively charged solution phase transition metal complexes to be transferred to the gas phase and studied by photoelectron spectroscopy for the first time. Experiments have been performed on a range of species, including classic square-planar and octahedral transition-metal halide complexes, metal-metal bonded species, transition metal bis(dithiolene) centers and a variety of mononuclear and polynuclear iron-sulfur clusters that are related to important bioinorganic centers. The studies have provided detailed information about the electronic structure and molecular orbital energy levels of these species, allowing for direct comparison with theoretical calculations, and providing insight into their intrinsic redox properties in the absence of solvation.

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
918842
Report Number(s):
PNNL-SA-49189
Journal ID: ISSN 0010-8545; CCHRAM; 2266; KP1303000; TRN: US200820%%20
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Coordination Chemistry Reviews, 251(3-4):474-491; Journal Volume: 251; Journal Issue: 3-4
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ELECTRONIC STRUCTURE; ENERGY LEVELS; HALIDES; IONIZATION; PHOTOELECTRON SPECTROSCOPY; TRANSITION ELEMENT COMPLEXES; Environmental Molecular Sciences Laboratory

Citation Formats

Waters, Tom, Wang, Xue B., and Wang, Lai S. Electroscopy Ionization Photoelectron Spectroscopy: Probing the Electronic Structure of Inorganic Metal Complexes in the Gas Phase. United States: N. p., 2007. Web. doi:10.1016/j.ccr.2006.04.010.
Waters, Tom, Wang, Xue B., & Wang, Lai S. Electroscopy Ionization Photoelectron Spectroscopy: Probing the Electronic Structure of Inorganic Metal Complexes in the Gas Phase. United States. doi:10.1016/j.ccr.2006.04.010.
Waters, Tom, Wang, Xue B., and Wang, Lai S. Thu . "Electroscopy Ionization Photoelectron Spectroscopy: Probing the Electronic Structure of Inorganic Metal Complexes in the Gas Phase". United States. doi:10.1016/j.ccr.2006.04.010.
@article{osti_918842,
title = {Electroscopy Ionization Photoelectron Spectroscopy: Probing the Electronic Structure of Inorganic Metal Complexes in the Gas Phase},
author = {Waters, Tom and Wang, Xue B. and Wang, Lai S.},
abstractNote = {The coupling of electrospray to photoelectron spectroscopy has allowed a number of negatively charged solution phase transition metal complexes to be transferred to the gas phase and studied by photoelectron spectroscopy for the first time. Experiments have been performed on a range of species, including classic square-planar and octahedral transition-metal halide complexes, metal-metal bonded species, transition metal bis(dithiolene) centers and a variety of mononuclear and polynuclear iron-sulfur clusters that are related to important bioinorganic centers. The studies have provided detailed information about the electronic structure and molecular orbital energy levels of these species, allowing for direct comparison with theoretical calculations, and providing insight into their intrinsic redox properties in the absence of solvation.},
doi = {10.1016/j.ccr.2006.04.010},
journal = {Coordination Chemistry Reviews, 251(3-4):474-491},
number = 3-4,
volume = 251,
place = {United States},
year = {Thu Feb 01 00:00:00 EST 2007},
month = {Thu Feb 01 00:00:00 EST 2007}
}
  • The electronic structures of a series of closely related U({eta}{sup 5}-C{sub 5}H{sub 5}){sub 3}L (L = -CH{sub 3}, -NH{sub 2}, -BH{sub 4}, - NCS) complexes has been studied using the SCF Hartree-Fock-Slater first-principles discrete variational X{alpha} method in combination with HeI and HeII UV photoelectron spectroscopy. The theoretical results reproduce the experimental HeI and He II photoelectron spectroscopic data, thus providing a reliable description of the metal-ligand bonding. 29 refs., 9 figs., 6 tabs.
  • A detailed understanding of the electronic structure of transition metal bis(dithiolene) complexes is important because of their interesting redox, magnetic, optical, and conducting properties and their relevance to enzymes containing molybdenum and tungsten bis(dithiolene) centers. The electronic structures of the bis(dithiolene) anions [M(mnt)2] n- (M ) Ni, Pd, Pt; mnt ) 1,2-S2C2(CN)2; n) 0-2) were examined by a combination of photodetachment photoelectron spectroscopy (PES) and density functional theory calculations. The combined experimental and theoretical data provide insight into the molecular orbital energy levels of [M(mnt)2]2- and the ground and excited states of [M(mnt)2]1- and [M(mnt)2]. Detachment features from ligand-based orbitalsmore » of [M(mnt)2]2- occur at similar energies for each species, independent of the metal center, while those arising from metal-based orbitals occur at higher energies for the heavier congeners. Electronic excitation energies inferred for [M(mnt)2]1- from the PES experiments agree well with those obtained in optical absorption experiments in solution, with the PES experiments providing additional insight into the changes in energy of these transitions as a function of metal. The singly charged anions [M(mnt)2]1- were also prepared and studied independently. Electron detachment from the ground states of these doublet anions accessed the lowest singlet and triplet states of neutral [M(mnt)2], thereby providing a direct experimental measure of their singlet-triplet splitting.« less
  • Comparative relativistic effective core potential ab initio calculations for both Th(IV) and U(IV) Cp[sub 3]AnL (Cp = [eta][sup 5]-C[sub 5]H[sub 5]; L = CH[sub 3], BH[sub 4]) complexes are reported. The Cp-An bonding appears to be dominated by metal 6d orbitals interacting with ligand [pi][sub 2] orbitals. Metal 5f orbitals provide a smaller contribution but are crucial for stabilization of the Cp[sub 3]An cluster. The stability of the An-CH[sub 3] bonding depends upon interactions involving metal 6d[sub g(2)]-based orbitals directed along the An-CH[sub 3] vector. The L BH[sub 4] ligand interactions are mediated by d[sub xz] and d[sub yz] atomicmore » orbitals, which are even better suited for favorable overlap and, hence, for greater metal-ligand [pi] covalency. Ground [sup 3]A[sub 2] states have been found to be the most stable for the U(IV) complexes. The experimental He I/He II photoelectron data are consistent with the quantum chemical calculations and indicate a close similarity between ground-state properties of the present Th(IV) and U(IV) complexes. 26 refs., 2 figs., 4 tabs.« less
  • Gas-phase photoelectron spectroscopy is used to investigate the bonding between early transition metals and carbonyl and cyclopentadienyl ligands. The lowest ionization energy region contains two overlapping ionizations that arise from the two orbitals that are occupied according to the formal d{sup 4} metal configuration. However, the character of these ionizations is dominated by the carbonyls rather than by the metals, as evidenced by the extensive C-O stretching vibrational progressions observed with these ionizations, by the trends in the ionization cross sections between the molecules and with different ionization sources, and by the relative lack of shifts of these ionizations withmore » metal substitution from vanadium to niobium to tantalum or with trimethylsilyl and acetyl substitutions on the cyclopentadienyl. The second group of ionizations for these molecules corresponds to orbitals with predominantly cyclopentadienyl {pi} character that donate to empty metal d orbitals. A much larger shift of these ionizations is observed upon cyclopentadienyl substitution. The molecular structures are sensitive to the electron configurations. Both density functional theory and ab initio calculations reproduce well the geometry of the neutral molecules and also predict the geometry changes upon ionization. The first ionization, which relates to an orbital with the a{sub 1} symmetry of the metal d{sub z}{sup 2} orbital, is broad due to a substantial geometry change upon removal of an electron from this orbital. The shoulder on the cyclopentadienyl-based ionizations related to a dynamic Jahn-Teller geometrical distortion. The unusually large metal-to-carbonyl back-bonding observed in these molecules is facilitated by the interligand overlap between the four carbonyls, which substantially stabilizes the appropriate symmetry-adapted carbonyl {pi}* acceptor orbitals. The extensive carbonyl character in the valence electronic structure diminishes any trends in properties with substitutions of the metals down the group or with substitutions on the cyclopentadienyl ring.« less