title: Spectroscopic and computational studies of a series of high-spin Ni(II) thiolate complexes.
abstract: The electronic structures of a series of high-spin Ni(II)-thiolate complexes of the form [PhTt(tBu)]Ni(SR) (R = CPh(3), 2; C(6)F(5), 3; C(6)H(5), 4; PhTt(tBu) = phenyltris((tert-butylthio)methyl)borate) have been characterized using a combined spectroscopic and computational approach. Resonance Raman (rR) spectroscopic data reveal that the nu(Ni-SR) vibrational feature occurs between 404 and 436 cm(-1) in these species. The corresponding rR excitation profiles display a striking de-enhancement behavior because of interference effects involving energetically proximate electronic excited states. These data were analyzed in the framework of time-dependent Heller theory to obtain quantitative insight into excited state nuclear distortions. The electronic absorption and magnetic circular dichroism spectra of 2-4 are characterized by numerous charge transfer (CT) transitions. The dominant absorption feature, which occurs at approximately 18,000 cm(-1) in all three complexes, is assigned as a thiolate-to-Ni CT transition involving molecular orbitals that are of pi-symmetry with respect to the Ni-S bond, reminiscent of the characteristic absorption feature of blue copper proteins. Density functional theory computational data provide molecular orbital descriptions for 2-4 and allow for detailed assignments of the key spectral features. A comparison of the results obtained in this study to those reported for similar Ni-thiolate species reveals that the supporting ligand plays a secondary role in determining the spectroscopic properties, as the electronic structure is primarily determined by the metal-thiolate bonding interaction.
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Van Heuvelen
authors.forename: Jaeheung
authors.initials: J
authors.lastname: Cho
authors.forename: Timothy
authors.initials: T
authors.lastname: Dingee
authors.forename: Charles G
authors.initials: CG
authors.lastname: Riordan
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Brunold
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*; D011789:Quantum Theory; D013059:Spectrum Analysis, Raman; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D013438:Sulfhydryl Compounds; D009532:Nickel