Electronic and photophysical properties of 2-(2′-hydroxyphenyl)benzoxazole and its derivatives enhancing in the excited-state intramolecular proton transfer processes: A TD-DFT study on substitution effect

摘要: Abstract The effect of electron donating and withdrawing substituents on the enol absorption keto emission spectra 2-(2′-hydroxyphenyl)benzoxazole (HBO) its derivatives has been systematically investigated by means density functional theory (DFT) time-dependent DFT (TD-DFT) methods. HBO were simulated using five different DFTs with various exchange-correlation functions to validate a suitable prior being further used as method choice study spectral characteristics derivatives. popular B3LYP (Becke, three-parameter, Lee–Yang–Parr) is found provide best desirable result in predicting spectrum close experimental data. In ground state, forms are more stable than those forms, while first lowest excited be their forms. Overall, from TD-B3LYP calculations good agreement For enol, maxima having electron-withdrawing groups red-shift corresponding lower HOMO–LUMO energy gaps compared that HBO. emission, (m-MeHBO MHBO) group (CNHBO) at 4′-position phenol fragment well (HBOMe HBOM) at 6-position benzoxazole make position peak shift shorter wavelength (blue-shift). However, (HBOF, HBOCl, HBOA HBOE) give redshifted parent compound (HBO). type substituent both 4′- 6-positions certainly pronounced