Temperature dependence of phenanthrene cavity radius in apolar solvents and in water

TL;DR

This study investigates how the cavity radius of phenanthrene in solvents varies with temperature, revealing an increase in organic solvents and a temperature-dependent behavior in water, linked to water structure changes.

Contribution

It provides new spectroscopic insights into the temperature-dependent cavity radius of phenanthrene in different solvents, especially water, and discusses water structure effects.

Findings

Cavity radius increases with temperature in organic solvents.

In water, the cavity radius initially grows then stabilizes at higher temperatures.

Water structure around phenanthrene strengthens at higher temperatures.

Abstract

Phenanthrene, a three ring aromatic hydrocarbon, is used as a model substance for study of intermolecular interactions in dilute solutions of organic solvents and water by spectroscopic method. Temperature dependencies of shift of the S$_2\leftarrow$S$_0$ spectrum of phenanthrene dissolved in apolar solvents and in liquid water are studied in this work. The spectroscopic data are used for analysis of the cavity radius $R$ for phenanthrene molecule in solvents. It is shown that the value of $R$ increases with temperature in organic solvents. In contrast, for water solution, the value of $R$ initially grows with temperature increase (in the interval of 273.3-296 K), but becomes constant at higher temperatures. The changes of water structure in the neighbourhood of a phenanthrene molecule and probable hypothesis about causes of $R$ value constancy in high-temperature region are discussed. Conclusion about strengthening of the water structure in an aqueous cage with phenanthrene molecule inside is done.