Crystal structure and photodimerization of 1-alkylthymine: Effect of long alkyl chain on isomer ratio of photodimer

Abstract

Crystal structure and photodimerization of 1-alkylthymine were studied in single crystals. Length of alkyl chains in 1-alkylthymine affected on crystal structure and photodimerization in single crystal. 1-Alkylthymine gave two types of crystals, Type 1 and Type 2 depending on length of alkyl chains and solvent used. This paper deals with Type 1 crystal, where thymine bases form plates by hydrogen bonding. UV irradiation at 280 nm on Type 1 crystals of 1-alkylthymine gave cyclobutane type photodimers. Crystals of 1-pentylthymine (C5), 1-nonylthymine (C9), and 1-decylthymine (C10) gave a trans-syn photodimer, but 1-octylthymine (C8) crystal gave a trans-anti photodimer. Alkyl chains played an important role in forming different isomers of photodimers.