LC-BLYP Calculations of the Structures an Photophysical Properties of [1,3]Thiazolo[4,5- b]pyrazine Derivatives in Cyclohexane an Methanol

Abstract

Copyright © 2019 American Chemical Society. Applications of the B3LYP an LC-BLYP functionals with the 6-311+G(,p) basis set for preicting absorption an fluorescence spectra of benzothiazole an 11 [1,3]thiazolo[4,5-b]pyrazine (TPy) erivatives in implicit solvents (cyclohexane an methanol) were teste an compare with experimental results. The amping parameter of LC-BLYP was tune for simulating absorption an fluorescence spectra of each compoun. For the 11 TPy erivatives, four an seven compouns are small- an meium-size TPy erivatives, respectively. From this calculation, TD-B3LYP can be use to simulate the absorption spectra of the small-size compouns in cyclohexane an methanol, but it gives poor results for the fluorescence spectra in cyclohexane an methanol. Contrarily, the LC-BLYP functional with the optimal amping parameter can reprouce the absorption an fluorescence spectra of all compouns in cyclohexane an methanol. The values of the amping parameter of LC-BLYP epen on the types of substituents an solvents. Moreover, the conformations of the compouns o not affect the spectra, an the molecular size an molecular ipole moment o not affect the amping parameter. In aition, types an the number of substitutions attache to the phenyl rings of TPy as well as solvent polarity play the key roles in the long-wavelength fluorescence emission an fluorescence brightness of the compouns. The intramolecular charge transfer of the compouns containing the -NMe2 an -CN groups is preominant in methanol, resulting in a large Stokes shift an oscillator strength.