title: Visible light sensitive cyclomer and its tautomeric dispiro compound formed from bispyridinyl diradical.
abstract: Two-electron reduction of 4,4'-(1,5-pentanediyl)bis(N-methylpyridinium) (52+) with sodium amalgam in degassed acetonitrile leads quantitatively to the formation of a cyclomer of 3,15-dimethyl-3,15-diazatricyclo[10.3.1.12,6]heptadeca-4,6(16),12(17),13-tetraene (6) by intramolecular cyclization. In degassed acetonitrile, 6 is stable for a long time at room temperature and, hence, a highly stable species. In contrast, 6 undergoes a photochemical reaction to give its valence tautomer having a dispiro structure, 3,10-dimethyl-3,10-diazadispiro[5.0.5.5]heptadeca-1,4,8,11-tetraene (7), when irradiated with visible light shorter than 450 nm. Noteworthy is the experimental fact that 7 is unstable to heat and, hence, reverts back to 6 by application of heat.
authors.affiliation: Environmental Education Center, Miyagi University of Education, Sendai 980-0845, Japan. t-mura@miyakyo-u.ac.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Muramatsu
authors.forename: Azumao
authors.initials: A
authors.lastname: Toyota
authors.forename: Miho
authors.initials: M
authors.lastname: Suzuki