Synthesis and photochromic properties of novel pyridine-containing diarylethenes

Abstract

Abstract Three isomeric pyridine-containing diarylethenes were synthesized to study the effects of nitrogen atom position ( ortho , para , meta ) on their photochromic properties. Among these diarylethenes, the example with the nitrogen atom at the ortho -position of pyridine displayed the largest absorption maximum and molar absorption coefficients. The cyclization quantum yields increased in order of para meta ortho , whereas their cycloreversion quantum yields decreased in order of para > meta > ortho . Compared to the diarylethene with terminal phenyl ring, those with a terminal pyridine showed enhanced cyclization quantum yields and emission intensities. Moreover, these pyridine-containing diarylethenes exhibited multi-addressable switching behavior under the stimulation of both proton and light. Addition of trifluoroacetic acid to the solutions of the diarylethenes resulted in notable color change, and their N-protonated forms also possessed excellent photochromism. These results indicated that the nitrogen atom position played a pivotal role in the process of photoisomerization of the diarylethenes.