Asymmetric, push-pull thiazolo[5,4-d]thiazole (TTz) fluorescent dyes have been developed for molecular sensing applications. The π-conjugated, TTz-bridged compounds are synthesized via a single-step condensation/oxidation of dithiooxamide and aromatic aldehydes containing one strong electron donating and one with strong electron accepting characteristics. The asymmetric TTz derivatives exhibit strong solvatofluorochromism with Stokes shifts between 2270 and 6050 cm<sup>-1</sup> and transition dipole moments (△μ = 13 – 18 D). Fluorescence quantum yields are as high as 0.93 in nonpolar solvents and the fluorescence lifetimes (τ<sub>F</sub>) vary from 1.5 to 3.0 ns depending on the solvent polarity. In addition, thermofluorochromic studies and spectrophotometric acid titrations indicate the possibility of using these dyes as temperature or acid sensors. In vitro cell studies indicate good cell membrane localization, insignificant cytotoxicity, promising voltage sensitivities, and photostabilities that are 4 times higher than comparable dyes. Their ease of synthesis and purification, remarkable photophysical properties, and chemically sensitive TTz π-bridge make these asymmetric dye derivatives attractive for environmental and biological sensing or similar molecular optoelectronic applications.

Voltage sensitive dyes based on solvatofluorochromic, push-pull thiazolothiazoles

ACS Spring Meeting 2021

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