Spectral manifestations of aggregates structure of heteroaromatic molecules at low temperatures

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Barashkov, N. N.
Korotkova, I. V.
Sakhno, T. V.
Короткова, Ірина Валентинівна
Сахно, Тамара Вікторівна
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Journal of Luminescence
The results of investigation of temperature in#uence on spectral-luminescence properties of ethanol solution of N,N-dibutyl-3,8-diazapyran-5,10-dione (DPD) in an interval of temperatures of 300}77 K and concentrations of 1.6.10~3-8.0.10~6 mol/l are discussed. The room-temperature absorption and #uorescence spectra of DPD remained constant in a broad interval of concentration. The lowering of temperature of a solution to 148 K leads to the reduction of the long wavelength band and the formation of two maxima (at 374 and 377.5 nm). It was found that their intensities’ ratio depend on concentration as well as on the method of freezing the solution. The low-temperature fuorescence spectra are short-wave shifted at 35 cm~1. The spectral modi"cations of rigid ethanol solutions of DPD were attributed to the formation of the associated forms of molecules due to van der Waals forces. Absorption spectra analysed at di!erent cooling rates revealed a ‘sandwicha structure of associates at a fast rate of freezing and ‘foota structure (angle 903) at a slow rate of cooling. The distance between the associated molecules of DPD was estimated to be about 11 A. The nature of spectral modi"cations due to associations of DPD molecules is discussed
Association; Fluorescence; Spectral manifestation