Abstract
Dienones (ketocyanine dyes) containing two aza-18-crown-6 ether residues were synthesized. The complex formation of these dyes with the EtNH3+ and +H3N(CH2)nNH3+ ions (n = 2–10, 12) in MeCN was studied by electronic and 1H NMR spectroscopy, including spectrophotometric and 1H NMR titration. It was found that homoditopic bis-azacrown dienones and alkanediammonium ions with a short polymethylene chain form 1:1, 2:2, and 1:2 complexes, whereas alkanediammonium ions with a long polymethylene chain form only pseudocyclic 1:1 complexes. The stability constants of the resulting complexes were determined (logK1:1 varies in the range from 2.74 to 5.62 [M–1], logK2:2 = 2.1 [M–1], and logK1:2 varies in the range from 2.03 to 2.96 [M–1]). The most stable complexes are formed by diammonium ions with a long polymethylene chain owing to simultaneous binding of both NH3+ groups to the azacrown ether residues of the dye. The structure of supramolecular complexes was confirmed by quantum chemical calculations.
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More From: Journal of Photochemistry & Photobiology, A: Chemistry
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