title: Photoelectron imaging and spectroscopy of MI(2)(-) (M = Cs, Cu, Au): evolution from ionic to covalent bonding.
abstract: We report a combined experimental and theoretical investigation of MI(2)(-) (M = Cs, Cu, Ag, Au) to explore the chemical bonding in the group IA and IB diiodide complexes. Both photoelectron imaging and low-temperature photoelectron spectroscopy are applied to MI(2)(-) (M = Cs, Cu, Au), yielding vibrationally resolved spectra for CuI(2)(-) and AuI(2)(-) and accurate electron affinities, 4.52 ± 0.02, 4.256 ± 0.010, and 4.226 ± 0.010 eV for CsI(2), CuI(2), and AuI(2), respectively. Spin-orbit coupling is found to be important in all the diiodide complexes and ab initio calculations including spin-orbit effects allow quantitative assignments of the observed photoelectron spectra. A variety of chemical bonding analyses (charge population, bond order, and electron localization functions) have been carried out, revealing a gradual transition from the expected ionic behavior in CsI(2)(-) to relatively strong covalent bonding in AuI(2)(-). Both relativistic effects and electron correlation are shown to enhance the covalency in the gold diiodide complex.
authors.affiliation: Department of Chemistry & Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Tsinghua University, Beijing 100084, China.
authors.forename: Yi-Lei
authors.initials: YL
authors.lastname: Wang
authors.forename: Xue-Bin
authors.initials: XB
authors.lastname: Wang
authors.forename: Xiao-Peng
authors.initials: XP
authors.lastname: Xing
authors.forename: Fan
authors.initials: F
authors.lastname: Wei
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Lai-Sheng
authors.initials: LS
authors.lastname: Wang