Intramolecular Interactions Between Thymine and Psoralen Induced by a Polyoxyethylene Chain

— The electronic absorption, fluorescence emission and photoreaction quantum yields for thymine-psoralen (1), psoralen-psoralen (2) and thymine-thymine (3) linked by triethyleneoxide chains are determined in ethanol and in water. Compounds (1), (2) and (3) are able to complex Li+ cations, new and striking effects of which have been revealed in their fluorescence properties and photoreactivities. An important hypochromism effect is observed in the UV spectrum of compound (1) in contrast to compounds (2) and (3).