Photochromism of new unsymmetrical isomeric diarylethenes bearing a methoxyl group

Abstract

Three new unsymmetrical isomeric diarylethenes having a methoxyl substituent at ortho-, meta-, and para-position of the terminal benzene ring, namely 1-(2,5-dimethyl-3-thienyl)-2-[2-methyl-5-(2-methoxylphenyl)-3-thienyl]perfluorocyclopentene (1o), 1-(2,5-dimethyl-3-thienyl)-2-[2-methyl-5-(3-methoxylphenyl)-3-thienyl]perfluorocyclopentene (2o), and 1-(2,5-dimethyl-3thienyl)-2-[2-methyl-5-(4-methoxylphenyl)-3-thienyl]perfluorocyclopentene (3o), have been synthesized. The substituent position effect of methoxyl group on their properties, including photochromism and fluorescence both in hexane solution and in PMMA film, and their electrochemical properties, were investigated in detail. These diarylethenes showed good photochromism both in solution and in PMMA film. For the same photochromic diarylethene backbone, the electrondonating methoxyl substituent can effectively depress the cyclization quantum yields and increase the cycloreversion quantum yields compared to those of diarylethenes bearing chlorine atoms reported previously. Diarylethenes 1o-3o showed clear fluorescent switches by photoirradiation both in hexane and in PMMA film. In addition, cyclic voltammetry tests showed that the electron-donating methoxyl group at different position on the terminal benzene ring had a significant effect on the electrochemical properties of these isomeric diarylethenes.

Effects of substitution on the optoelectronic properties of photochromic diarylethenes bearing a pyrrole moiety

“…When comparing samples in hexane to those in PMMA films, the emission peaks of diarylethenes 2oe5o consistently exhibited a hypsochromic shift with values of 3 nm for 2o, 16 nm for 3o, 15 nm for 4o, and 4 nm for 5o, respectively. The result is completely contrary to those reported previously [16,34,36,46]. Among diarylethenes 1oe5o, the emission peak of the unsubstituted parent diarylethene 3o was at the longest wavelength and its emission intensity was the strongest in hexane and in PMMA films.…”

“…Similarly, the fluorescent modulation efficiency was increased by 16% for 2, 10% for 3, 13% for 4, and 20% for 5 in hexane, respectively, compared with that in PMMA films. The result was completely contrary to those of the unsymmetrical diarylethene derivatives whose fluorescent modulation efficiencies in hexane are much lower than those in PMMA films [18,34,46]. However, our findings were in agreement with that of diarylethene derivatives bearing a thiazole moiety [40,52].…”

Photochromism of a novel asymmetrical diarylethene with a (formyloxyethoxy)ethyl‐linked naphthalimide moiety

“…Compared with those in methanol, the absorption maxima of the closed‐ring isomers in PMMA films were bathochromic shifted by 7 nm for both 1c and 2c . The result was in good agreement with that of the reported diarylethenes . The reason may be attributed to the polar effect of the polymer matrix and stabilization of molecular arrangement in solid media …”

A multi‐addressable molecular switch based on a novel diarylethene with an imidazo [4,5‐f] [1,10] phenanthroline unit

“…Compare with that in chloroform, the absorption maxima of the closed‐ring isomer in a PMMA film was observed at longer wavelength, with the bathochromic shift value of 7 nm for 1C . The result is in good agreement with the date for most of the reported diarylethenes . The reason may be ascribed to polar effect of the polymer matrix and the stabilization of molecular arrangement in solid medium.…”