Document Detail

Dynamics and mechanism of structural diffusion in linear hydrogen bond.
MedLine Citation:
PMID:  22009491     Owner:  NLM     Status:  Publisher    
Dynamics and mechanism of proton transfer in a protonated hydrogen bond (H-bond) chain were studied, using the CH(3) OH(2) (+) (CH(3) OH)(n) complexes, n = 1-4, as model systems. The present investigations used B3LYP/TZVP calculations and Born-Oppenheimer MD (BOMD) simulations at 350 K to obtain characteristic H-bond structures, energetic and IR spectra of the transferring protons in the gas phase and continuum liquid. The static and dynamic results were compared with the H(3) O(+) (H(2) O)(n) and CH(3) OH(2) (+) (H(2) O)(n) complexes, n = 1-4. It was found that the H-bond chains with n = 1 and 3 represent the most active intermediate states and the CH(3) OH(2) (+) (CH(3) OH)(n) complexes possess the lowest threshold frequency of proton transfer. The IR spectra obtained from BOMD simulations revealed that the thermal energy fluctuation and dynamics help promote proton transfer in the shared-proton structure with n = 3 by lowering the vibrational energy for the interconversion between the oscillatory shuttling and structural diffusion motions, leading to a higher population of the structural diffusion motion than in the shared-proton structure with n = 1. Additional explanation on the previously proposed mechanisms was introduced, with the emphases on the energetic of the transferring proton, the fluctuation of the number of the CH(3) OH molecules in the H-bond chain, and the quasi-dynamic equilibriums between the shared-proton structure (n = 3) and the close-contact structures (n ≥ 4). The latter prohibits proton transfer reaction in the H-bond chain from being concerted, since the rate of the structural diffusion depends upon the lifetime of the shared-proton intermediate state. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011.
Sermsiri Chaiwongwattana; Mayuree Phonyiem; Viwat Vchirawongkwin; Supakit Prueksaaroon; Kritsana Sagarik
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-10-18
Journal Detail:
Title:  Journal of computational chemistry     Volume:  -     ISSN:  1096-987X     ISO Abbreviation:  -     Publication Date:  2011 Oct 
Date Detail:
Created Date:  2011-10-19     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9878362     Medline TA:  J Comput Chem     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2011 Wiley Periodicals, Inc.
School of Chemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand.
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