The H•/H-Redox Couple and Absolute Hydration Energy of H-

Ashley S. McNeill, Chang Guo Zhan, Aaron M. Appel, David M. Stanbury, David A. Dixon

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


A supermolecule-continuum approach with water clusters up to n = 16 H2O molecules has been used to predict the absolute hydration free energies at 298 K (ΔGhyd) of both hydrogen (H•) and hydride (H-) to be 4.6 ± 1 and -78 ± 3 kcal/mol, respectively. These values are combined with a high accuracy prediction of the gas-phase electron affinity (ΔGgas,298K = -16.9 kcal/mol) to determine the aqueous electron affinity of H•of 99.5 ± 3 kcal/mol, which yields a reduction potential for H•vs SHE of -0.03 ± 0.15 V. This value is in agreement within 0.2 V with most estimates obtained using a wide variety of approaches. These results can be used to improve the absolute hydricity scale in water which provides additional insights into how a putative hydride interacts with solvent but do not change the ability to predict the relative reactivity of two species using relative hydricity scales.

Original languageEnglish
Pages (from-to)6084-6095
Number of pages12
JournalJournal of Physical Chemistry A
Issue number29
StatePublished - Jul 23 2020

Bibliographical note

Publisher Copyright:
Copyright © 2020 American Chemical Society.

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry


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