Photochemistry of pyridine substituted 1,3-butadiynes

Abstract

Pyridine substituted 1,3-butadiynes were synthesized through several coupling methods in order to investigate the effect of pyridyl substituent on photophysical and photochemical properties, topochemical polymerization and photocycloaddition reaction of 1,3-butadiynes. These 1,3-butadiynes showed strong phosphorescence emission and higher excited triplet energy than that of phenyl substituted 1,3-butadiynes. The pyridine substituted butadiynes were more reactive for topochemical polymerization by UV light irradiation and annealing than phenyl substituted 1,3-butadiynes although the yields were low. 6-(2-Pyridyl)-3,5-hexadiyn-1-ol was polymerized in the presence of water at room temperature, which was identified with visible, IR, and Raman spectra. When 1-phenyl-4-(2-pyridyl)-1,3-butadiyne was irradiated with dimethyl fumarate, 1:1 photoadducts containing cyclobutene ring were obtained as major products and 1:2 photoadduct containing cyclopropane ring was obtained as one of byproducts.