American Chemical Society, The Journal of Physical Chemistry A, 48(116), p. 11870-11879, 2012
DOI: 10.1021/jp3084293
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Benzoic acid (BA) derivatives of environmental relevance exhibit various photophysical and photochemical characteristics. Here, time-dependent density functional theory (TDDFT) is used to calculate photoexcitations of eight selected BAs and the results are compared with UV spectra determined experimentally. High-level gas phase EOM-CCSD calculations and experimental aqueous phase spectra were used as the references for the gas-phase and aqueous-phase TDDFT results, respectively. A cluster-continuum model was used in the aqueous-phase calculations. Among the 15 exchange-correlation (XC) functionals assessed, five functionals, including the meta-GGA hybrid M06-2X, doubly hybrid B2PLYPD, and range-separated functionals CAM-B3LYP, ωB97XD and LC-ωPBE, were found to be in excellent agreement with the EOM-CCSD gas phase calculations. These functionals furnished excitation energies consistent with the pH dependence of the experimental spectra with a standard deviation (STDEV) of ~0.20 eV. A molecular orbital analysis revealed a πσ* feature of the low-lying transitions of the BAs. The CAM-B3LLYP functional showed the best overall performance, and therefore shows promise for TDDFT calculations of processes involving photoexcitations of benzoic acid derivatives.