Photochromic Performance of 5-Heteroaryl-4-vinyl-2-phenylthiazole Derivatives

Abstract

Abstract Compounds 5-(5-methyl-2-phenyl-4-thiazolyl)-4-(5-methyl-1-phenyl-1-propenyl)-2-phenylthiazole 1a and 5-(2-methyl-5-phenyl-3-thienyl)-4-(2-methyl-1-phenyl-1-propenyl)-2-phenylthiazole 2a having an S-N heteroatom-contact interaction and a CH-N hydrogen bonding were synthesized in an attempt to obtain new photochromic compounds having terarylene and 1-aryl-2-vinylcyclopentene backbones. The S-N interaction and CH-N hydrogen bonding of 1a and 2a can be explained by DFT calculation and temperature dependent 1H NMR spectra. The tethering interactions are expected to stabilize the reactive conformation of 1a and 2a, and to increase the photocyclization quantum yield. Two 5-heteroaryl-4-vinyl-2-phenylthiazoles 1 and 2 underwent reversible photocyclization reactions from the open-ring isomers 1a and 2a to the closed-ring isomers 1b and 2b, respectively. The photocyclization quantum yields of 1a and 2a are 0.57 and 0.63, which are 3 times larger than that of 1-thiazolyl-2-vinylcyclopentene derivatives (0.20). The number of photochromic cycles exhibited by 1b was 50 in the presence of air, which is higher than that of 2b.