On the photophysical behaviour of 4-halo-5-phenylisoxazoles

Abstract

Detailed spectral and photophysical properties of 4-halo-5-phenylisoxazoles in cyclohexane solutions are presented, including measurements of energies of lowest excited singlet and triplet states, fluorescence quantum yields, lifetimes, phosphorescence and triplet–singlet difference absorption spectra. Upon addition of ethanol, loss of vibrational structure is observed in fluorescence spectra and attributed to formation of isoxazole–ethanol aggregates. The relevance of these properties to the photochemical and thermal reactivity of these systems is discussed.