Benzimidazole-derived calix[4]arenes with polymerizable styrene groups and their Cu(II) complexes

Abstract

p-tert-Butylcalix[4]arene [C4(OH)4] was substituted with one to four benzimidazole groups at the phenolic positions affording the compounds C4(OH)3(OBzIm)–C4(OBzIm)4. The solid-state structures confirmed the cone conformation of all derivatives. A tetrasubstituted calix[4]arene with two benzimidazole groups and two 4-methylenestyryl in distal positions C4(OStyr)2(OBzIm)2, which are amenable for polymerization reactions, was also obtained. The monobenzimidazole compound C4(OH)3(OBzIm) reverts to a partial-cone conformation on binding CuCl2, giving rise to the dimeric complex [C4(OH)2(OBzIm)2]2[CuCl(μ-Cl)]2 in the solid state, featuring N and O-coordination from the benzimidazole–N and ethereal–O atoms towards the Cu2+ ions placed outside the calixarene cavity. In contrast, the tetrasubstituted C4(OStyr)2(OBzIm)2 gives rise to the crystallographically-characterized monomeric complex [C4(OStyr)2(OBzIm)2CuCl2], with the cupric ion located directly above the macrocyclic cavity. This complex has 4-methylenestyryl groups at two distal phenolic positions, ideally poised for further modifications, including polymerization of the copper-containing monomer.