Molecular simulations allow us to disassemble the aqueous photoelectron spectra and the half-cell redox potentials of dissolved molecules into simpler, component thermodynamic quantities. We simulated the spectra produced by aqueous liquid microjet photoelectron spectroscopy (PES) for several small molecules using explicitly solvated quantum chemical models. <i>Ab initio</i> simulation results exhibited agreement with the positions and widths of experimental spectral bands obtained at the BESSY II Synchrotron (HZB) to within 0.1–0.3 eV. By using molecular simulations to describe the aqueous PES and the component processes of the half-cell one-electron redox reaction, we are able to: (1) quantify the influence of aqueous solvent on the electronic energy levels of organic molecules; (2) estimate the aqueous vertical ionization energy distribution (PES bands) for any small organic molecule, including compounds that are inaccessible by experiment; (3) differentiate the electronic contributions of proximate water molecules versus the approximately 3000 outerlying water molecules that participate in the vertical transition; (4) further evaluate the relationships between the aqueous vertical ionization energy, the half-cell one-electron redox potential, and a reorganization energy formulated according to an electrochemical definition; and (5) isolate and estimate several distinct thermodynamic sub-quantities that, when added together, provide the one-electron redox potential.

Taking apart the aqueous photoelectron spectra and one-electron redox potentials of dissolved compounds with molecular simulations

251st National Meeting (2016)

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