The effects of heteroaryl ring on the photochromism of diarylethenes with a naphthalene moiety

Three new asymmetrical naphthalene-containing diarylethenes with different heteroaryl groups have been synthesized to investigate the heteroaryl effects on their properties. The three diarylethenes exhibited distinctive photochromism with good thermal stability, which may be attributed to the different heteroaryl effects. Their cycloreversion quantum yields increased in the order of 2-methylbenzofuran < 2-methylbenzothiophene < 1,2-dimethylindole, while the cyclization quantum yields exhibited a reverse trend. Compared to indole and benzothiophene, the benzofuran moiety could effectively shift the absorption maximum to a shorter wavelength and notably enhance the cyclization quantum yield and fluorescence quantum yield of the diarylethene. The results indicated that the category of heteroaryl groups played a vital role during the process of photoisomerization of naphthalene-containing diarylethene derivatives.