Ion-pair receptors bear recognition sites for both an anion and a cation. Such receptors may bind a cation and an anion either as an intact ion pair or as separate ions. We have synthesized  bis(3-bromoindol-2-ylmethyl)(2-pyridylmethyl)amine (1), in which two indolyl NH groups bind an anion and two amine/pyridine N atoms bind a cation. The cation and anion binding behavior in solution, as separate ions or an ion-pair, was demonstrated using ESI-MS, 1H NMR and UV-Vis spectroscopy. Titrations, by 1H NMR, were performed to determine the association constants of the various ions binding to the synthesized receptor 1. A cooperative binding of an ion pair was demonstrated. DFT (density functional theory) calculations support the ability of receptor 1 to bind an intact ion pair. Colorimetric studies were performed to ascertain the possibility of using the synthesized receptor 1 as an ion-specific sensor.

Spectroscopic studies of a new ion-pair receptor

244th National Meeting (2012)

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