Iodine photocatalyzed cis → trans isomerization of 3-styrylpyridine. Role of charge transfer complex

Abstract

The iodine photocatalyzed cis → trans isomerization of 3-styrylpyridine has been investigated in n-hexane at 25°C by irradiation at 408, and 478 nm where the free and complexed iodine absorb competitively. The mechanism of the free and complexed iodine photocatalysis is the same, the charge-transfer complex with styrylpyridine dissociating to give two iodine atoms with a lower yield (φ₄₇₈= 0.2) than molecular iodine (φ₄₇₈= 0.5). Some experiments with stilbene gave similar results. The mechanism is discussed with respect to that reported for stilbene.