Abstract
Recently, a new method [P. Partovi-Azar and D. Sebastiani, J. Chem. Phys. 152, 064101 (2020)] was proposed to increase the efficiency of proton transfer energy calculations in density functional theory by using the T state with additional optimized effective potentials instead of calculations at S. In this work, we focus on proton transfer from six prototypical photoacids to neighboring water molecules and show that the reference proton dissociation curves obtained at S states using time-dependent density functional theory can be reproduced with a reasonable accuracy by performing T calculations at density functional theory level with only one additional effective potential for the acidic hydrogens. We also find that the extra effective potentials for the acidic hydrogens neither change the nature of the T state nor the structural properties of solvent molecules upon transfer from the acids. The presented method is not only beneficial for theoretical studies on excited state proton transfer, but we believe that it would also be useful for studying other excited state photochemical reactions.
Highlights
Many fundamental chemical processes are triggered when the electrons in a system are excited
We find that a better agreement with the reference TDDFT calculations can be reached by adapting the following optimization procedure: (i) we optimize r0 and h012 to obtain the correct proton transfer energies; (ii) using these optimized parameters, we optimize h022 and again r0 to reach the correct values for the transition energies
We have proposed and optimized a specific form of effective potentials for acidic hydrogens to improve the efficiency of density functional theory calculations in predicting energies and barriers of proton transfer reactions at excited state
Summary
Many fundamental chemical processes are triggered when the electrons in a system are excited. The interaction of a molecule with its environment at an electronic excited state can be largely different from that in the electronic ground state. It has become possible to indirectly investigate the nature of such interactions as well as structural properties of solvents by studying the change in properties of molecular probes upon excitation [1,2,3,4,5]. Photoinduced proton transfer in solutions is of fundamental interest in a large variety of chemical and biological applications such as energy storage systems and sensors [12,13,14,15,16,17,18].
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