Fluorescent properties anionic derivative of thioflavin T

We have investigated the spectral properties of a new benzothiazole dye – thioflavin T derivative 3-sulfopropyl-5-methoxy-2-[3-(3,5-diethyl-2-benzothiazolidene)-1-propienyl]-benzothiazolium (Th-C11). Based on quantum-chemical calculations, it is shown that molecule in ground state has flat structure. In an excited state, minimum energy corresponds to twisted conformation, which aromatic fragments are arranged orthogonally. Since non-fluorescent, transition this (torsion relaxation) quenching process. Th-C11 exhibits fluorescent molecular rotor. As result experimental studies, was found torsion relaxation main process determines strong dependence quantum yield and duration fluorescence decay viscosity solvent. A characteristic feature sensitivity parameters yield, position spectrum not only viscosity, but also polarity medium. The paper explains absorption spectra solvent as manifestation processes solvation chromophore molecules.