Solvent Dependence of Double Proton Transfer in the Formic Acid

Sep 6, 2017 - Department of Chemistry, Faculty of Science, Chiang Mai University, ... Graduate School of Arts and Science, The University of Tokyo, 4-...
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Solvent Dependence of Double Proton Transfer in the Formic Acid Formamidine Complex: Path Integral Molecular Dynamics Investigation Nawee Kungwan, Chanisorn Ngaojampa, Yudai Ogata, Tsutomu Kawatsu, Yuki Oba, Yukio Kawashima, and Masanori Tachikawa J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.7b07010 • Publication Date (Web): 06 Sep 2017 Downloaded from http://pubs.acs.org on September 11, 2017

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The Journal of Physical Chemistry

Solvent Dependence of Double Proton Transfer in the Formic Acid - Formamidine Complex: Path Integral Molecular Dynamics Investigation

Nawee Kungwana,b*, Chanisorn Ngaojampaa,b, Yudai Ogatac, Tsutomu Kawatsuc,d, Yuki Obac, Yukio Kawashimae and Masanori Tachikawac,*

a

Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand

b

Center of Excellence in Materials Science and Technology, Chiang Mai University, Thailand c

Graduate School of Nanobioscience, Yokohama City University, 22-2 Seto, Yokohama-City, Kanagawa 236-0027, Japan d

Graduate School of Arts and Science, The University of Tokyo, 4-6-1 Komaba, Meguroku, Tokyo 153-8902, Japan

e

Advanced Institute for Computational Science, RIKEN,7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan

*

Corresponding

author. E-mail: [email protected] (N. Kungwan) and

tachi@yokohama-

cu.ac.jp (M. Tachikawa). Fax: +66 53 892 277 and +81 48 858 3700

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The Journal of Physical Chemistry

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ABSTRACT Solvent dependence of double proton transfer in the formic acid–formamidine (FA-FN) complex at room temperature was investigated by means of ab initio path integral molecular dynamics (AIPIMD) simulation with taking nuclear quantum and thermal effects into account.

The

conductor-like screening model (COSMO) was applied for solvent effect. In comparison with gas phase, double proton delocalization between two heavy atoms (O and N) in FA-FN were observed with reduced proton transfer barrier height in low dielectric constant medium (4.8), the ionic species becomes more stable than the neutral ones and the formate anion and formamidium cation are thermodynamically stable. For ab initio molecular dynamics simulation, in low dielectric constant medium (