抄録
Conformational peculiarity of 10-(9H-xanthenylidene)-9 (10H)-anthracenone was studied in relation to the temperature effect in the photochemical cyclization and reduction reactions. On the basis of the experimental result that the temperature effect is negative for the former reaction but positive for the latter reaction, it was concluded that the population of the planar structure of the above molecule in solution decreases gradually at higher temperatures in favor of a twisted structure which contributes to the radical formation. This conclusion is consistent with the results of our previous polarographic and electron spin resonance studies of some thermochromic ethylenes. On the other hand, the planar structure of the molecule appears to be predominant over a wide range of temperature in the crystal state.
