New receptors for anions in water: Synthesis, characterization, X-ray structures of new derivatives of 5,11,17,23-tetraamino-25,26,27,28-tetrapropyloxycalix[4]arene

Syntheses and characterization of ten new compounds from the calixarene family, cone – 5,11,17,23- tetrakis(2-pyridylmethylamino)-25,26,27,28-tetrapropyloxycalix[4]arene 4a; cone – 5,11,17,23-tetrakis(3-pyridylmethylamino)-25,26,27,28-tetrapropyloxycalix[4]arene 4b; cone – 5,11,17,23-tetrakis(4-pyridylmethylamino)-25,26,27,28-tetrapropyloxycalix[4]arene 4c; cone – 5,11,17,23-tetrakis(ferrocenylmethylamino)-25,26,27,28-tetrapropyloxycalix[4]arene 4d; cone – 5,11,17,23-tetrakis(2-pyridylmethimino)-25,26,27,28-tetrapropyloxycalix[4]arene 3a; cone – 5,11,17,23-tetrakis(3-pyridylmethimino)-25,26,27,28-tetrapropyloxycalix[4]arene 3b; cone – 5,11,17,23-tetrakis(4-pyridylmethimino)-25,26,27,28-tetrapropyloxycalix[4]arene 3c; cone – 5,11,17,23-tetrakis(ferrocenylmethimino)-25,26,27,28-tetrapropyloxycalix[4]arene 3d; cone – 5,11,17,23-tetrakis(2-thienylmethimino)-25,26,27,28-tetrapropyloxycalix[4]arene 3e and cone – 5,11,17,23-tetrakis(2-pyrrolylmethimino)-25,26,27,28-tetrapropyloxycalix[4]arene 3f are reported. The target compounds 4a–4d were designed to form complexes with anions based on hydrogen bonds and electrostatic interactions in acidic aqueous solutions and the interaction constant 1770 mol−1 dm3 of a 1:1 complex was obtained for the interaction of 4c with sulfate anion in 5 × 10−3 M aqueous HCl. The solid state structures of the compounds 3b, 3e and 3f were determined, their stereochemistry and the stereochemistry of the calix[4]arene frame is generally discussed. Raman, infrared and UV–vis spectra of the target compounds and some intermediates are reported, too.