A path integral molecular dynamics study on the muoniated xanthene-thione molecule

Kazuaki Kuwahata; Shigekazu Ito; Masanori Tachikawa

doi:10.1063/5.0159207

A path integral molecular dynamics study on the muoniated xanthene-thione molecule

J Chem Phys. 2023 Sep 14;159(10):104301. doi: 10.1063/5.0159207.

Authors

Kazuaki Kuwahata¹, Shigekazu Ito², Masanori Tachikawa¹

Affiliations

¹ Graduate School of Nanobioscience, Yokohama City University, Yokohama, Japan.
² School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo, Japan.

PMID: 37681697
DOI: 10.1063/5.0159207

Abstract

A positive Mu is a useful tool for investigating the spin density of radical species. The theoretical estimation of its behavior in a molecule requires the inclusion of a quantum effect due to the small mass of muonium. Herein, we performed ab initio a path integral molecular dynamics (PIMD) simulation, which accurately included a multi-dimensional quantum effect, for muoniated 9H-xanthene-9-thione (μXT). Our results showed that the quantum effect significantly increased the hyperfine coupling constant (HFCC) value of μXT, which qualitatively improved the calculated HFCC value, compared to the experimental one. In the PIMD simulation, the bond length between muonium and sulfur in μXT is longer than that between hydrogen and sulfur in a hydrogenated 9H-xanthene-9-thione (HXT), leading to a spin density transfer from XT (9H-xanthene-9-thione) to muonium due to neutral dissociations. Additionally, we found that the S-Mu bond in μXT prefers a structure perpendicular to the molecular plane, where the interaction between Mu and the singly occupied molecular orbital of μXT is the strongest. These structural changes resulted in a larger HFCC value in the PIMD simulation of μXT.