A model study on the mechanism and kinetics for the dissociation of water anion

Trinh Le Huyen, Long Van Duong, Minh Tho Nguyen*, Ming Chang Lin

*Corresponding author for this work

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

Quantum chemical computations using both density functional theory (B3LYP functional) and wavefunction (MP2 and CCSD(T)) methods, with the 6-311++G(3df,2p) and aug-cc-pVnZ (n = D,T,Q) basis sets, in conjunction with a polarizable continuum model (PCM) method for treating structures in solution, were carried out to look again at a series of small negatively charged water species [(H2O)n]•–. For each size n of [(H2O)n]•– in aqueous solution with n = 2, 3, and 4, two distinct structural motifs can be identified: a classical water radical anion formed by hydrogen bonds and a molecular pincer in which the excess electron is directly interacting with H atoms. In aqueous solution, both motifs have comparable energy content and likely coexist and compete for the ground state. Some water anion isomers can dissociate when interaction with a water molecule, [(H2O)n]•– + H2O → H(H2O)m + OH(H2O)nm, through successive hydrogen transfers with moderate energy barriers. This reaction can also be regarded as a water-splitting process in which the H transfers involved take place mainly within a water trimer, whereas other water molecules tend to stabilize transition structures through microsolvation rather than direct participation. Calculated absolute rate constants for the reversed reaction H(H2O)2 + OH(H2O)2 → [(H2O)4]־ + H2O with both H and D isotopes agree well with the experimentally evaluated counterpart and lend a kinetic support for the involvement of a tetramer unit.

Original languageEnglish
Pages (from-to)610-617
Number of pages8
JournalInternational Journal of Chemical Kinetics
Volume51
Issue number8
DOIs
StatePublished - Aug 2019

Keywords

  • dissociation of water anions
  • hydrated electrons
  • reactions of water anions
  • water anions
  • water split by water anions

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