Excited state intramolecular proton transfer of 2-(2′,6′-dihydroxyphenyl)benzoxazole: Insights using computational methods

The photo-physical behaviour of 2-(2′,6′-dihydroxyphenyl) benzoxazole was studied using the Density Functional Theory (DFT), Time Dependent Density Functional Theory (TD-DFT) and Configuration Interaction Singles (CIS). Different functionals including the hybrid and M06X series were used to compute the absorption and emission. Experimental absorption and emission wavelengths are in good agreement with those predicted using TD-DFT [TD-B3LYP/6-31 G(d)]. The further improvement was not observed with the larger basis sets like 6-31 G(d,p) and 6-311 G(d,p). The rotational barrier was also calculated theoretically in chloroform (10.5-14.1 kcal/mol) and it was found to be close to the experimental energy value (10.5 kcal/mol).