title: B4CO2: a new, observable sigma-pi diradical.
abstract: A new sigma-pi diradical, B4(CO)2, prepared in matrix isolation, was characterized unambiguously by isotopic-substitution infrared spectroscopy and by theoretical computations. Both open-shell singlet and triplet states have three pi electrons but are aromatic with moderately large NICS values. Quantum chemical calculations at various levels indicate that the open-shell singlet is slightly more stable than the triplet state. However, the singlet and triplet are computed to have very similar IR features which do not allow experimental differentiation.
authors.affiliation: Department of Chemistry, Fudan University, Shanghai 200433, P.R. China. mfzhou@fudan.edu.cn
authors.forename: Mingfei
authors.initials: M
authors.lastname: Zhou
authors.forename: Qiang
authors.initials: Q
authors.lastname: Xu
authors.forename: Zhi-Xiang
authors.initials: ZX
authors.lastname: Wang
authors.forename: Paul von Ragué
authors.initials: Pv
authors.lastname: Schleyer