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Proton dissociation and transfer in hydrated phosphoric acid clusters
Author(s) -
Suwannakham Parichart,
Chaiwongwattana Sermsiri,
Sagarik Kritsana
Publication year - 2015
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.24873
Subject(s) - dissociation (chemistry) , proton , chemistry , molecular dynamics , chemical physics , molecule , computational chemistry , proton transport , organic chemistry , physics , quantum mechanics
The dynamics and mechanisms of proton dissociation and transfer in hydrated phosphoric acid (H 3 PO 4 ) clusters under excess proton conditions were studied based on the concept of presolvation using the H 3 PO 4 –H 3 O + – n H 2 O complexes ( n = 1–3) as the model systems and ab initio calculations and Born–Oppenheimer molecular dynamics (BOMD) simulations at the RIMP2/TZVP level as model calculations. The static results showed that the smallest, most stable intermediate complex for proton dissociation ( n = 1) is formed in a low local‐dielectric constant environment (e.g., ε = 1), whereas proton transfer from the first to the second hydration shell is driven by fluctuations in the number of water molecules in a high local‐dielectric constant environment (e.g., ε = 78) through the Zundel complex in a linear H‐bond chain ( n = 3). The two‐dimensional potential energy surfaces (2D‐PES) of the intermediate complex ( n = 1) suggested three characteristic vibrational and 1 H NMR frequencies associated with a proton moving on the oscillatory shuttling and structural diffusion paths, which can be used to monitor the dynamics of proton dissociation in the H‐bond clusters. The BOMD simulations over the temperature range of 298–430 K validated the proposed proton dissociation and transfer mechanisms by showing that good agreement between the theoretical and experimental data can be achieved with the proposed rate‐determining processes. The theoretical results suggest the roles played by the polar solvent and iterate that insights into the dynamics and mechanisms of proton transfer in the protonated H‐bond clusters can be obtained from intermediate complexes provided that an appropriate presolvation model is selected and that all of the important rate‐determining processes are included in the model calculations. © 2015 Wiley Periodicals, Inc.