Formation of intermediate gas–liquid system in aromatics’ thin layers Scientific paper

Abstract

The present work discusses IR spectroscopic experiments and quan­tum-chemical DFT study of structure and intermolecular binding in the inter­mediate gas–liquid systems of aromatics, namely, benzene, furane, pyridine and thiophene. These systems can be generated in thin layers near a solid su­r­face by two different methods, depending on the physical properties of the sample. The first method includes evaporation with a subsequent compression of a sample in an optical cell of variable thickness, and it is applied to volatile components: benzene, furane, thiophene. For benzene and pyridine the second method is used, which involves a heating-initiated evaporation into a closed inter-window space with an after-cooling of a sample. It was shown that the formed layer is not an adsorbate or a condensate. The IR data obtained by these two methods lead to conclusion that the given systems of the considered aro­m­atics manifest dual gas–liquid spectral properties which can change each into other by varying external conditions. According to the DFT calculation results, the spatial arrangement in the aromatic thin layers can be described as a com­bination of π- and σ-bonded clusters, which simulate the gas and the liquid phase state properties.