Jump to main content
Jump to site search


Molecular Electrostatic Potential on the Proton-Donating Nucleus as a Theoretical Descriptor of Excited State Acidity

Abstract

Organic photoacids with enhanced acidities in the excited states have received much attention both experimentally and theoretically because of their applications in nanotechnology and chemistry. In this study, we investigate excited-state acidities of 14 hydroxyl-substituted aromatic photoacids, with a focus on using theoretical molecular electrostatic potential (MEP) as an effective descriptor for photoacidity. For these model photoacids, we applied time-dependent density functional theory (TDDFT) at the $\omega$B97X-D/6-31G(d) level to calculate molecular electrostatic potential of $S_1$ excited states and show that the molecular electrostatic potential on the proton-donating atom exhibit a linear relationship with the observed excited-state logarithmic acid dissociation constant (p$K_{a}^{*}$). As a result, the molecular electrostatic potential on the proton-donating atom can be used to estimate p$K_{a}^{*}$ values based on simple TDDFT calculations for a broad range of hydroxyl-substituted aromatic compounds. Furthermore, we explore molecular electrostatic potential as a quantum descriptor for photoacidities of cationic photoacids, and show an universal behavior of the p$K_{a}^{*}$-MEP dependence. We also investigate solvent effects on the photoacidity using TDDFT calculations with implicit solvent models. Finally, we discuss the physical insights implicated by molecular electrostatic potential as a successful measure for photoacidity on the mechanism of proton transfer in the molecular excited states. This p$K_{a}^{*}$ descriptor provides an effective means to quantify the tendency of excited-state proton transfer with a relatively small computational cost, which is expected to be useful in the design of functional photoacids.

Back to tab navigation

Supplementary files

Publication details

The article was received on 27 Mar 2017, accepted on 03 Jan 2018 and first published on 03 Jan 2018


Article type: Paper
DOI: 10.1039/C7CP01948C
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
  •   Request permissions

    Molecular Electrostatic Potential on the Proton-Donating Nucleus as a Theoretical Descriptor of Excited State Acidity

    Y. Wang and Y. Cheng, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C7CP01948C

Search articles by author

Spotlight

Advertisements