Synthesis and the optoelectronic properties of diarylethene derivatives having benzothiophene and n-alkyl thiophene units

Abstract

Six new unsymmetrical diarylethenes having both benzothiophene and n-alkylthiophene units have been synthesized. The structures of diarylethenes 2a– 6a were determined by single-crystal X-ray diffraction analysis. The results showed that the alkyl chain length had a significant effect on the optoelectronic properties of these diarylethenes, including photochromism, fatigue resistance, fluorescence and electrochemical properties. The long alkyl chains can increase the cyclization/cycloreversion quantum yields but decrease the absorption maxima of diarylethenes 1– 6. The long alkyl chains can also induce a remarkable bathochromic shift for the absorption maxima of the closed-ring isomers 1b– 6b both in solution and in PMMA film. All these diarylethene derivatives showed good fluorescent switching (quench to ca. 10%) in hexane. The emission intensities and the fluorescent quantum yields of diarylethenes 1– 6 decreased gradually with the alkyl chain length becoming longer. In addition, cyclic voltammetry tests showed that the alkyl chain length had a remarkable effect on the electrochemical behaviors of these diarylethenes.