Formation of intermediate gas-liquid system in aromatics’ thin layers

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 ?- and ?-bonded clusters, which simulate the gas and the liquid phase state properties.