Optical switching and fluorescence modulation properties of photochromic dithienylethene derivatives

Fluorescent photoswitching molecules in which photochromic diarylethene with terpyridine units (tpy) attached via a phenylene linker to the thiophene rings were synthesized. Both compounds exhibited pronounced photochromic properties. Irradiation of the open form of compounds 1 and 2 with UV light resulted in immediate photocyclization to the blue closed form; the colorless open forms could be regenerated by irradiation with visible light. In terms of potential use for optical data storage and readout, compounds 1 and 2 display fluorescence discrimination between their open and closed form. This fluorescence switching could be the basis of a nondestructive readout method. And the complexation of these two compounds with metal ions was also studied. It is amazing to find the addition of Zn2+ lead the emission wavelengths of 2a red shift up to 105 nm. This unique phenomenon makes the compound 2a, a candidate for the chemical sensor for zinc.