Theoretical studies on structures and stabilities of C 4 H 2 + isomers

The structures, energies, stabilities and spectroscopies of doublet C 4 H 2 + cations were explored at the DFT/B3LYP/6-311G( d , p ), CCSD(T)/6-311+G(2 df ,2 pd )(single-point), and G3B3 levels. Ten minimum isomers including the chainlike, three-member-ring, and four-member-ring structures are interconverted by means of 15 interconversion transition states. The potential energy surface was investigated. At the CCSD(T)/6-311+G(2 df ,2 pd ) and G3B3 levels, the global minimum isomer was found to be a linear HCCCCH. The structures of the stable isomer and its relevant transition state are further optimized at the QCISD/6-311G( d , p ) level. The bonding nature and structure of isomer HCCCCH were analyzed.