Theoretical investigations on forward–backward ESIPT processes of three fluorophores deriving from 2-(2′-hydroxyphenyl)thiazole

The photophysical properties and excited-state intramolecular proton transfer (ESIPT) processes for 2-(2′-hydroxyphenyl)-4-chloromethylthiazole (1), 2-(2′-hydroxyphenyl)-4-phenylthiazole (2), 2-(2′-hydroxyphenyl)-4-hydroxymethyl-thiazole (3) were studied at the TD-B3PW91/6–31 + G(d, p)/IEFPCM level. structures of 1–3 fully optimized corresponding structural parameters, infrared spectra electron densities in ground (S0) first excited (S1) states analyzed. calculated absorption fluorescence wavelengths reproduced experimental data. potential energy curves S0 S1 built ESIPT clarified. Our results showed that H-bonds 3 2 state strongest weakest, respectively, then barriers lowest highest, respectively. Among three phenol-thiazole type probes, compound with phenyl ring group 4 position thiazole had larger π-conjugation, higher barrier same time. 1 CH2Cl CH2OH lower barrier.