Optical recognition elements. Macrocyclic imidazole chromoionophores entrapped in silica xerogel

Materials containing new chromoionophores consisting of crown residue and azole moiety as parts of macrocycles were encapsulated by the sol-gel procedure in silica xerogel matrices and proposed as chemical recognition elements especially for such metal ions as Li+, Cs+ and Cu2+. Action of these recognition elements is in principle based on changes of reflectance. The recognition elements containing 21- membered chromogenic derivatives of unsubstituted imidazole and 4-methylimidazole are able to distinguish in aqueous solution whether the Li+ concentration ratio is lower or higher than 1. In the case of Cu2+ complexes with 18-membered macrocyclic chromoionophore in which phenol residue was replaced by imidazole and 21-membered chromogenic derivative of 4-methylimidazole, values of the EPR parameters g and A suggest participation of two oxygen and two nitrogen atoms of the ligand in the equatorial plane of the tetragonally distorted octahedral environment of the central ion.