New dithiacrown-ether butadienyl dyes: synthesis, structure, and complex formation with heavy metal cationsстатья

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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.

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[1] New dithiacrown-ether butadienyl dyes: synthesis, structure, and complex formation with heavy metal cations / A. I. Vedernikov, E. N. Ushakov, L. G. Kuz'mina et al. // Journal of Physical Organic Chemistry. — 2010. — Vol. 23, no. 3. — P. 195–206. Benzothiazole type butadienyl dyes containing a dithia-15-crown-5 (2a) or dithia-18-crown-6 ether (2b) moieties were synthesized. The structures of dyes 2a,b and their complexes with Ag(+) and Pb(2+) were studied by an X-ray crystallography. It was found that the conformations of dithiacrown-ether moieties of dyes 2a,b are unfavorable for complex formation and change significantly upon binding of Ag(+) or Pb(2+). The complexation of 2a,b with Ag(+), Cd(2+), Pb(2+), and Hg(2+) in water-acetonitrile mixtures with different contents of water (P(w) = 0-75%, v/v) was studied by (1)H NMR, UV-Vis spectroscopy, and polarography. In anhydrous acetonitrile, the stability constants of 1:1 complexes change in the sequence Cd(2+) < Pb(2+) <= Ag(+) << Hg(2+) in the case of 2a and in the sequence Cd(2+) < Ag(+) < Pb(2+) << Hg(2+) in the case of 2b. As P(w) increases, the thermodynamic stability of Ag(+) complexes increases. The opposite effect is observed for the complexes with Cd(2+), Pb(2+), and Hg(2+). When P(w) similar to 50%, the stability constants of complexes with Cd(2+) and Pb(2+) become too small to be measured. The selectivity of ligands 2a,b toward Hg(2+) versus Ag(+) is very high at any P(w) values (selectivity coefficients > 10(4)). The complexation of 2a,b with Hg(2+) at P(w) <= 50% is accompanied by a substantial hypsochromic effect. This allows dithiacrown-containing butadienyl dyes to be used as selective optical molecular sensors for heavy metal ions, in particular, in aqueous solutions. Copyright (C) 2009 John Wiley & Sons, Ltd. [ DOI ]

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