MethyleneCycloPropene: Local Vision of the first 1 B 2 excited state

International audienceThe 1 A 1 ground and the first 1 B 2 excited states of the methylenecyclopropene (triafulvene) are described by localized wave functions, based on 20 structures Valence Bond structures. The results are compared to CASSCF(4,4) calculations for both the energetics and the dipole moment. Additional calculations with partial electronic delocalization are presented, and it is shown that the dipole moment modification does not correspond to a situation where the antiaromatic situation prevails (with 4n electrons in the cycle). Part of the analysis uses a "trust factor" that helps to decide if a wave function is appropriate to describe a given state. The trust factor compares the VB wave function to the CASSCF's with their overlap. Finally, the Valence Bond density is used to produce density maps that illustrate the electron transfer upon excitation