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Issue 3, 2006
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Photoinduced and dark complexation of unsaturated viologen analogues containing two ammonium tails with cucurbit[8]uril

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Abstract

Complex formation between cucurbit[8]uril (CB[8]) and unsaturated viologen analogues 1a,b bearing two ammoniopropyl substituents was studied using 1H NMR spectroscopy and X-ray diffraction. The complex stability constants were measured by 1H NMR titration. CB[8] was found to encapsulate 1,2-di(4-pyridyl)ethylene derivative (E)-1a in water/acetonitrile solution to form only inclusion complex of 1 : 1 composition. The high stability of CB[8]·1a (lg K1:1 ≥ 5) is apparently due to the possibility of hydrogen bond formation between two NH3+ groups of 1a and the O[double bond, length as m-dash]C fragments of both portals of CB[8]. Contrarily, the derivative of 1,2-di(4-quinolyl)ethylene (E)-1b gave three types of inclusion complexes upon mixing with CB[8]. The stability of the 1 : 1 complex (lg K1:1 = 4.6) is decreased compared to (E)-1a, suggesting a poorer fit with respect to the bulky (E)-1b in the cavity of CB[8] for the simultaneous hydrogen bonding of the both ammonium groups. This is the driving force for the formation of an unusual 2 : 1 complex, {CB[8]}2·(E)-1b. The expanded π-system of (E)-1b allows also two tetracationic molecules of the acceptor to form a 1 : 2 complex owing to stacking interactions. Crystallization of a 1b/CB[8] mixture under irradiation resulted in an inclusion complex of the Z-isomer of 1b. The supramolecular complex is formed because the shape of (Z)-1b fits well to the host cavity and the ammonium groups form a system of hydrogen bonds with oxygen atoms of both portals of CB[8]. The features of crystalline complexes CB[8]·(Z)-1b and CB[8]·HClO4 are discussed.

Graphical abstract: Photoinduced and dark complexation of unsaturated viologen analogues containing two ammonium tails with cucurbit[8]uril

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Publication details

The article was received on 11 Aug 2005, accepted on 09 Jan 2006 and first published on 01 Feb 2006


Article type: Paper
DOI: 10.1039/B511456J
Citation: New J. Chem., 2006,30, 458-466
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    Photoinduced and dark complexation of unsaturated viologen analogues containing two ammonium tails with cucurbit[8]uril

    L. G. Kuz’mina, A. I. Vedernikov, N. A. Lobova, J. A. K. Howard, Y. A. Strelenko, V. P. Fedin, M. V. Alfimov and S. P. Gromov, New J. Chem., 2006, 30, 458
    DOI: 10.1039/B511456J

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