On the electronic structure of cubene C₈H₆

Hartree-Fock (HF) and multiconfiguration Hartree-Fock (MCHF) wavefunctions of cubene C₈H₆ have been calculated which indicate that the ground state ¹A₁ of the molecule is better described as a diradical than a CC double bonded structure. The ³B₂ state is found to lie ≈ 0.94 eV above the ground state and the ¹B₂ state ≈ 4.4 eV above the ground state. The dissociation energy for β-CH bond cleavage in the cubyl radical C₈H₇ to form C₈H₆(¹A₁) + H is estimated to be 74 kcal/mol compared to 91 kcal/mol for CH bond cleavage in cubane C₈H₈ to form C₈H₇ + H. β-CH bonds in the cubyl radical are much stronger than β-CH bonds in acyclic alkyl radicals.