Definitive evidence for the contribution of biradical character in a closed-shell molecule, derivative of 1,4-bis-(4,5-diphenylimidazol-2-ylidene)cyclohexa-2,5-diene

Azusa Kikuchi; Fumiyasu Iwahori; Jiro Abe

doi:10.1021/ja049423h

Definitive evidence for the contribution of biradical character in a closed-shell molecule, derivative of 1,4-bis-(4,5-diphenylimidazol-2-ylidene)cyclohexa-2,5-diene

J Am Chem Soc. 2004 Jun 2;126(21):6526-7. doi: 10.1021/ja049423h.

Authors

Azusa Kikuchi¹, Fumiyasu Iwahori, Jiro Abe

Affiliation

¹ Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University, and The 21st Century COE Program, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 229-8558, Japan.

PMID: 15161260
DOI: 10.1021/ja049423h

Abstract

This study provides conclusive proof that the thermally excited open-shell state with biradical character is contributing to the ground state of a closed-shell molecule, tF-BDPI-2Y, where four hydrogen atoms at the central phenylene ring are substituted with four fluorine atoms of 1,4-bis-(4,5-diphenylimidazol-2-ylidene)cyclohexa-2,5-diene (BDPI-2Y). A small increase in the population of biradical species of tF-BDPI-2Y results in the formation of the dimer form by the radical recombination reaction. Controlling the equilibrium between a closed-shell diamagnetic-quinoid state and an open-shell paramagnetic-biradical state will provide significant progress in the field of pi-conjugated delocalized biradical chemistry.