Ultraviolet-visible spectroscopic study of 3,5-dithio-2,7-dimethyl-[1,2,4]-triazepine: qualitative analysis of tautomeric behaviour |
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Authors: | Azzouzi F Lyazidi S Ait Haddad M El Messaoudi M Hasnaoui A Larbi N Ben |
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Institution: | Laboratoire de Spectronomie Physique, Faculté des Sciences, Université Moulay Ismail, BP 4010, Beni M'hamed, Meknès, Morocco. |
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Abstract: | Room temperature UV-vis absorption spectra of the tautomeric system 3,5-dithio-2,7-dimethyl-1,2,4]-triazepine in solution, in acetonitrile (CH3CN), are measured at different water volume percentages. The comparison of the obtained measures to the calculated allowed absorption transitions, using ZINDO/S package, reveals the coexistence of all the tautomeric forms in aprotic polar solution with a high dominance of the dithione form. The solute-water hydrogen bond, which seems to be of 1:n-type, favours the dithiol and monothiol conformers to the detriment of the dithione one. Further experimental investigations lead to the result that standing at ambient Laboratory conditions in the dark favours the dithione tautomeric isomer, while standing at indirect sunlight shifts the tautomeric equilibrium away from this species. |
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Keywords: | UV– vis absorption Tautomers Dithione Dithiol Hydrogen bond Dark/indirect sunlight effect |
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