Geometric and electronic structures of V₂C^-₂ and V₂C₂ studied by photoelectron spectroscopy and density-functional calculations

The electronic and geometric structures of V₂C₂^- were investigated by photoelectron spectroscopy (PES) and density-functional theory (DFT). The experimental PES spectrum was compared with the simulated ones for several low-energy isomers obtained by the structural optimization procedure. The spectrum is found to be best reproduced by the most stable isomer, which has a doublet spin multiplicity and a planar distorted four-membered-ring geometry with a transannular V-C bonding. The VC₂ subunit in V₂C₂^- is almost identical with the optimized structure of free VC₂. The DFT study of V₂C₂ shows that it has the singlet ground state with a geometry similar to that of the anion.