Abstract
Abstract: Phenylacetylene interacts with triethylamine in the excited state. Hence, the formation of weak charge transfer binary molecular complex species popularly known as exciplex has been investigated. The exciplex is formed probably due to the interaction of the excited state phenylacetylene dipole and C-H dipole of triethylamine in the non-polar aprotic solvent cyclohexane. Exciplex formation is very much dependent on the concentration of triethylamine. Higher concentrations of triethylamine facilitate the formation of exciplex. Phenylacetylene absorbs at 271 nm wavelength, and it shows a fluorescence emission peak at 298 nm. While titrating phenylacetylene against triethylamine in cyclohexane, a new emission band centered on 422 nm is observed and indicates the formation of exciplex. In cyclohexane, in higher quencher (triethylamine) concentration (above 14.2 mM), the inaccessible fraction of phenylacetylene is 0.48±0.06 (≈0.5), which is a close resemblance of multi-tryptophan protein in water, where half of the sites are solvent inaccessible. At lower concentrations of triethylamine, the fluorescence quenching of phenylacetylene is predominantly dynamic, but at higher concentrations, it is complex. In ethanol, the quenching of fluorescence is purely dynamic. Therefore, in very high concentrations of triethylamine, fluorescence is almost saturated. The effect of solvent polarity on molecular aggregation of phenylacetylene with triethylamine has been studied.
Published Version
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