Photophysical, electrochemical, and spectroelectrochemical investigation of electronicpush–pullbenzothiadiazole fluorophores

Abstract

Two electronic push-pull fluorophores consisting of a benzothiadiazole core and a terminal N,N-dimethylamino electron donating group were prepared. The effect of the terminal electron withdrawing group (-NO 2 and -CN) on the spectroscopic, electrochemical, and spectroelectrochemical properties were examined. The fluorophores were solvatochromic with Stokes shifts upward of 9000 cm −1 being observed in aprotic solvents of varying polarity. It was found that the fluorophores fluoresced appreciably (86 % > Φ fl > 18 %) in hexane, toluene, diethyl ether, dichloromethane, ethyl acetate, and THF. The fluorescence was quenched in acetonitrile, acetone, and DMSO. The fluorophores also fluoresced appreciably in thin films when embedded in poly(methyl methacrylate) and poly(dimethylsiloxane) matrices. Protonating the terminal amine with trifluoroacetic acid quenched the intramolecular charge transfer band, although the fluorophores remained fluorescent. The fluorophores could also be reversibly oxidized electrochemically. The resulting oxidized state was visually different than the neutral form. Electrochemical oxidation also led to reversible changes in both the fluorescence wavelength and intensity.

Electroluminochromic Materials: From Molecules to Polymers

“…Skene et al reported two push-pull N,N -dimethylamino-benzothiadiazole fluorophores, M11a and M11b , which were found to exhibit solvochchromism, electrochromic and electrofluorochromic properties [29]. Thin film of M11a with a terminal cyano group changed visible colour from yellow to mauve upon oxidation, with fluorescence colour correspondingly changing from purple to blue.…”

Textile Based Electrochromic Cells Prepared with PEDOT: PSS and Gelled Electrolyte

“…Besides inorganic thin layers, organic and metal-organic compounds can also exhibit electrochromism. These compounds are, e.g., small molecules like benzothiadiazole fluorophores, bipyridylium salts (also called viologens), and electrically conductive polymers like derivatives of polyaniline (PAni) and polythiophene (PT) [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. These polymers exist in a broad variety of oxidation states, which all appear in a different color, e.g.…”

Electrochromism and electrochemical properties of complexes of transition metal ions with benzimidazole-based ligand

“…2 Very interesting are compounds exhibiting socalled multielectrochromism: various low redox states derived from distinct absorption bands at different wavelengths. Inorganic metal oxides, [3][4][5] organic conjugated polymers [6][7][8] or small molecules [9][10][11] are typical materials for electrochromic uses.…”