Multi-addressable molecular switches based on photochromic diarylethenes bearing a rhodamine unit

Abstract

Two novel diarylethene derivatives bearing a rhodamine unit have been successfully synthesized. Their unique multi-addressable switching characteristics as induced by chemical and optical dual inputs stimulation were observed using UV and FL measurements. The two diarylethenes showed excellent photochormism with alternating UV/vis light irradiation. Addition of trifluoroacetic acid (TFA) protonated the diarylethenes, which resulted in good photochromism and notable fluorescence change via the FRET mechanism. Subsequent addition of triethanolamine base would neutralize and return both their protonated open-ring and closed-ring isomers to their original forms. It was found that the diarylethene bearing a rhodamine unit linked by a benzhydrazide bridge group was more sensitive, efficient and reacted faster to protonation by TFA when compared to the benzamide bridged derivative. Furthermore, the benzhydrazide bridged diarylethene derivative was found to be selective towards Cr(III), Al(III), or Ca(II) with significant color and fluorescence changes.