PHOTODIMERIZATIONS AND CRYSTAL-STRUCTURES OF THYMINE DERIVATIVES HAVING A LONG ALKYL CHAIN CONNECTED WITH A CARBAMATE BOND

Photodimerizations of thymine derivatives having a long alkyl chain on a carbamate bond were investigated by irradiation of UV light at 280 nm in amorphous and crystalline film states. The amorphous films obtai ned by spin-coating from chloroform solution had higher initial rate c onstants for photodimerization relative to those of the crystalline fi lms after annealing. X-Ray crystal structure analysis showed that the thymine derivatives had intermolecular hydrogen bonds that led to disa dvantageous molecular orientation for the photodimerization. The photo dimerization, however, is preferred in the localized layer structures of thymine units and alkyl chain.