AB-INITIO MO STUDY OF THE GEOMETRIES AND ENERGETICS OF THE C3H- ANION

The molecular structures of various conformers of the C3H- anion were studied using complete active space SCF and QCISD(T) methods. A Huzina ga-Dunning split-valence (or double-zeta) plus polarization (D95v* or D95*)basis set was used. The relative stability ladder of the comput ed stationary points and their relative positions on the potential ene rgy surface are discussed using single- and multi-reference SDCI with the Davidson correction and CCSD(T); the general contraction scheme of the [5s3p2d1f/3s2p1d] atomic natural orbitals and the 6-311 + + G(2d, p) basis sets were applied, respectively. The global minimum of the C 3H- anion is a C-2v singlet ((1)A(1)) with a C-3 ring, which is aromat ically stabilized due to the 4n + 2 (n = 0) tau electrons in the C-3 r ing. Below the theoretical electron detachment energy of the anion (2. 3 eV), (1)A(1), several electronic states, (1) Delta, (3)A'', (1)A'' a nd (1)A', with different symmetries are predicted.