Excited state proton transfer mechanism of a thiazolo [5,4-d] thiazole derivative in different solvents

Abstract

In this paper, the excited state proton transfer mechanism of a thiazolo [5,4-d] thiazole derivative, 4-tert-butyl-2-(5-(5-tert-butyl-2-methoxyphenyl) thiazolo [5,4-d] thiazol-2-yl) phenol (MTTH), has been investigated in different polar solvents by using DFT and TDDFT methods. The hydrogen bond lengths, bond angles, and corresponding infrared vibrational frequencies of MTTH in three different polar solvents were compared, and the analytical results showed that the intramolecular hydrogen bonding of MTTH was enhanced in all S1 states. In addition, the simulated absorption and emission spectra values of MTTH are in good agreement with the experimental data, which further proves the rationality of the calculation method. Meanwhile, the electron density rearrangement between the proton acceptor and donor was found by analyzing the frontline molecular orbitals of the MTTH, which is favorable for the excited state proton transfer process. Finally, the potential energy curves of MTTH in three different solvents were calculated, and the results indicated that the weakly polar solvents were more favorable for the excited state intramolecular proton transfer of MTTH.