Unexpected Solute Occupancy and Anisotropic Polarizability in Lewis Basic Solutions

Siyan Gao; Yongli Huang; Xi Zhang; Chang Q Sun

doi:10.1021/acs.jpcb.9b05745

Unexpected Solute Occupancy and Anisotropic Polarizability in Lewis Basic Solutions

J Phys Chem B. 2019 Oct 10;123(40):8512-8518. doi: 10.1021/acs.jpcb.9b05745. Epub 2019 Sep 30.

Authors

Siyan Gao¹, Yongli Huang¹, Xi Zhang², Chang Q Sun³

Affiliations

¹ School of Materials Science and Engineering , Xiangtan University , Hunan 411105 , China.
² Institute of Nanosurface Science and Engineering , Shenzhen University , Shenzhen 518060 , China.
³ NOVITAS, School of Electrical and Electronic Engineering , Nanyang Technological University , Singapore 639798 , Singapore.

PMID: 31525987
DOI: 10.1021/acs.jpcb.9b05745

Abstract

Density functional computation revealed that in YOH solvation (Y = Li, Na, and K), the Y⁺ cation locates eccentrically at the interstitial hollow site to form the Y⁺·4H₂O unit, and the hydroxyl adds an excessive electron lone pair ":" to form a OH^-·H₂O unit where the hydroxide stays in the the center. The surrounding four oriented H₂O neighbors interact with the Y⁺ through Y⁺ ↔ H⁺ repulsion and Y⁺:O^2- attraction, causing the Y⁺ eccentric dislocation by some 0.80 Å. The ":" turns one O:H-O bond into the O: ⇔ :O super hydrogen bond by altering H₂O·4H₂O into HO^-·4H₂O. The repulsive Y⁺ ↔ H⁺ enlarges its separation and the attractive Y⁺:O shortens itself, showing the anisotropic polarization of the Y⁺ cation. The anisotropic Y⁺ polarizability, O: ⇔ :O compressibility, and the H-O bond contraction of the solute OH^- distorts the solute bonding network and disperses the O:H-O segmental phonon frequencies, as confirmed spectroscopically.