Study of tin- and tin cluster-cyano complexes using anion photoelectron spectroscopy and density functional calculations

The photoelectron spectra of SnCN-, SnCH2CN-, Sn(CN)(2)(-), Sn(CN)(CH2CN)(-), Sn2CN-, Sn2CH2CN-, Sn3CN-, Sn3CH2CN-, and Sn4CN- have been obtained and analyzed, and density functional calculations (B3LYP/LANL2DZ and B3LYP/LANL2MB) have been performed on the SnCN, Sn(CN)(2), Sn2CN, and Sn3CN anions and neutrals. From the spectra of the singly ligated complexes, the ground and low-lying excited neutral states are inferred to be predominantly ionic (Snx+CN- or Snx+CH2CN-). These states are accessed by detaching an electron from what is nominally a neutral tin atomic or tin cluster orbital in the anionic complex (SnxCN- or SnxCH2CN-). In all cases, the SnxCN- and SnxCH2CN- spectra show similar electronic structure, though in the case of the latter, electronic structure is more vibrationally congested and shifted to lower binding energy. The spectra of SnCN-, Sn(CN)(2)(-), and Sn(CN)(CH2CN)(-) exhibit a nearly 400 cm-1 vibrational spacing. SnCN/SnCN- and Sn(CN)(2)/Sn(CN)(2)(-) are linear and planar, respectively. The spectra of SnCN- and SnCH2CN- show an approximately 0.3 eV spin-orbit splitting. The spectrum of Sn2CN- shows transitions to two neutral electronic states; the excited state band exhibits a short, partially resolved 190(50) cm(-1) vibrational progression. Analysis of the spectrum of Sn2CN- and density functional theory (DFT) calculations suggest planar structures for the anion and two neutral states. The spectra of Sn3CN-, Sn3CH2CN-, and Sn4CN- show multiple, vibrationally congested electronic bands. The electronic structures of all the complexes are described qualitatively in the ionic limit. (C) 2000 American Institute of Physics. [S0021-9606(00)01027-8].