Chromogenic anion molecular probes based on β,β′-disubstituted calix[4]pyrroles

The reaction of octamethylcalix[4]pyrrole with 3-(dimethylamino)prop-2-enal and POCl3 affords a mixture of isomeric calix[4]pyrroles bearing two formylethenyl groups at the beta-pyrrolic positions. These dialdehydes were used in Knoevenagel reactions with malononitrile and indene-1,3-dione leading to new chromogenic anion molecular probes. The binding ability of the new receptors was investigated by UV-vis spectroscopy and NMR, indicating the formation of supramolecular 1:2 host:guest complexes with high affinity constants. (C) 2014 Elsevier B.V. All rights reserved.