抄録
The perpendicularly twisting conformation of an anion radical of 10-(α-(o-tolyl)-benzylidene)-9 (10H)-anthracenone was studied by the use of electron spin resonance (ESR) measurement. By comparison with previous results on 10-diphenylmethylene-9 (10H)-anthracenone and 10 (9-xanthenylidene)-9 (10H)-anthracenone, it was found that this structural feature of the compound was a result of the presence of the carbonyl group. Semi-empirical molecular orbital calculations with an open shell model revealed a correlation between the twisting angle about the central double bond of anion radicals of some thermochromic ethylenes and the π-electronic charge distribution on the double bond, and were found to be in reasonable agreement with the conclusion obtained from ESR measurements. It became apparent that twisting decreased the double bond character of the central double bond. A qualitative interpretation of the distribution of the unpaired electron in the molecule is presented.
