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Photoinduced protonation and mechanical motion in the cyclodextrin cavity: Synthesis, structure and spectral properties of 4-(2-napthyl)pyridine and their pseudorotaxane complexesстатья
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
- Авторы: Gromov S.P., Nazarov V.B., Avakyan V.G., Fomina M.V., Vedernikov A.I., Kuz'mina L.G., Vershinnikova T.G., Lobova N.A., Rudyak V.Y., Alfimov M.V., Howard J.A.K
- Журнал: Journal of Photochemistry and Photobiology A: Chemistry
- Том: 217
- Номер: 1
- Год издания: 2011
- Издательство: Elsevier BV
- Местоположение издательства: Netherlands
- Первая страница: 87
- Последняя страница: 99
- DOI: 10.1016/j.jphotochem.2010.09.022
- Аннотация: The spontaneous and photoinduced protonation of 4-(2-naphthyl)pyridine (1) in solutions and in complexes with beta-cyclodextrin (beta-CD) and 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) were studied by absorption and fluorescence spectroscopy. The structure and stability of the complexes (log K = 1.5-2.3) of 1, its protonated form 2, and quaternized derivative, 1-methyl-4-(2-naphthyl)pyridinium perchlorate (3), with beta-CD and HP-beta-CD were studied by (1)H NMR. It was shown that irrespective of the solution pH, compound 1 resides in the cyclodextrin cavity. HP-beta-CD better binds the neutral form of 1 than beta-CD, while naphthylpyridinium salts have approximately equal binding affinity to both cyclodextrins. The structures of salt 3 and pseudorotaxane complex 1@beta-CD were determined by X-ray diffraction analysis. According to spectral data, pK(a) of 1 in water is 5.12, which promotes protonation of nitrogen both in the ground state and in the excited state. As a consequence, the fluorescence spectrum exhibits only the protonated form with a lifetime of 15 ns. The addition of HP-beta-CD to a solution of 1 results in inclusion complex 1@HP-beta-CD; simultaneously pK(a) of 1 decreases to 4.62 and non-protonated form fluorescence (NFF) of 1 with a lifetime of 1.25 ns appears. Thus, the residence of 1 in the HP-beta-CD cavity hampers its protonation in the excited state. From comparison of the initial regions of fluorescence of 1 in solution and in the HP-beta-CD complex after pulse excitation, a mechanism for appearance of short-lived NFF of 1 was proposed. Quantum chemical simulation of the protonation and complexation of 1 in the presence of water was performed. On the basis of results, reversible photoinduced mechanical motion of 1 in the HP-beta-CD cavity was suggested. (C) 2010 Elsevier B.V. All rights reserved.
- Добавил в систему: Громов Сергей Пантелеймонович