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

Abstract

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.