O2 solvation cavity in voids of ionic liquids studied by the solvatochromic red shift of O2(1Δg) phosphorescence

Tsuyoshi Yoshida; Masayuki Okoshi; Akio Kawai

doi:10.1063/5.0073955

O₂ solvation cavity in voids of ionic liquids studied by the solvatochromic red shift of O₂(¹Δ_g) phosphorescence

J Chem Phys. 2021 Dec 21;155(23):234503. doi: 10.1063/5.0073955.

Authors

Tsuyoshi Yoshida¹, Masayuki Okoshi¹, Akio Kawai²

Affiliations

¹ Department of Electrical and Electronic Engineering, National Defense Academy, 1-10-20, Hashirimizu, Yokosuka, Kanagawa 239-8686, Japan.
² Department of Chemistry, Faculty of Science, Kanagawa University, 2946 Tsuchiya, Hiratsuka-shi, Kanagawa 259-1293, Japan.

PMID: 34937375
DOI: 10.1063/5.0073955

Abstract

Phosphorescence spectroscopy of singlet oxygen [=O₂(¹Δ_g)] was applied to study the solvation properties of small solute molecule, O₂, in ionic liquids. Unlike conventional molecular solvents, the spectral red shift of the O₂(¹Δ_g) phosphorescence in ionic liquids from the gas phase was found to depend not only on the refractive index of solvents but also on the vdW volume of anions. This unusual spectral shift of the O₂(¹Δ_g) luminescence is interpreted by considering the size of solvation cavities in voids, which is estimated by analyzing the free volume in ionic liquids. These results suggest the potential of the O₂(¹Δ_g) phosphorescence spectral shift measurement in the study of molecular-scale voids in ionic liquids.