Luminescence and photoreactivity of 2,5-distyrylpyrazine crystals

Abstract

The emission spectra of the photolabile polymerizable distyrylpyrazine (DSP) in its α-crystallographic modification have been studied in the form of both fresh and partially polymerized samples.

A photochromism in emission is observed which is attributed to excitonic and monomeric emissions. At room temperature, fresh DSP single crystals of the α-modification give emission spectra with two maxima at 500 and 530 nm. During the photopolymerization a new emission peak develops at ca. 445 nm which is attributed to isolated monomer molecules being separated by the photoproduct from the exciton. The position of this developing peak compares with the emission from dilute DSP methanolic and chloroform solutions.

The photopolymerization process obeys a zero-order kinetic law, and a kinetic study of the as-grown DSP single crystals reveals a negative energy of activation, E_a=–(38.15±1.6) kJ mol^–1.