Microhydration effects on geometric properties and electronic absorption spectra of ortho-aminobenzoic acid

• Simulation of the theoretical electronic absorption spectra of ortho-aminobenzoic acid by TD-DFT.
• Use of microhydration and PCM models to obtain spectra in aqueous medium.
• Analysis of geometric properties as well as intermolecular and intramolecular hydrogen bonds.
• When more water molecules surround ortho-aminobenzoic acid, the spectrum resembles the experimental data more closely.
• Microhydration and PCM models are necessary to fit the spectrum correctly.

TD-DFT and a combination of polarized continuum model (PCM) and microhydration methods helped to simulate the optical electronic absorption spectrum of ortho-aminobenzoic acid (o-Abz). The microhydration method involved the use of different numbers, from 1 to 5, of first solvation layer water molecules. We examined how implicit and explicit water affected the energies of the HOMO–LUMO transition in the o-Abz/water systems. Adding until five water molecules, the theoretical spectrum becomes closer to the experimental data. Microhydration combined with the PCM method leads to agreement between the theoretical result for five water molecules and the experimentally measured absorption bands.

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