Synthesis and crystal structures of meso-substituted calix[4]pyrrole mono-Schiff bases and transition metal complexes

Abstract

A series of 5,5-dialkyl-10,10,20,20-tetraethyl-15-methyl-15-(4-nitrophenyl)calix[4]pyrroles were efficiently synthesized from acid catalyzed condensation of diethyldipyrromethanes with p-nitroacetophenone and further cyclization with other ketones. The corresponding calix[4]pyrrole mono-Schiff bases were obtained by sequential reductive hydrogenation of above 15-(4-nitrophenyl)calix[4]pyrroles and condensation with salicylaldehyde and pyridinecarboxaldehyde. Furthermore, the copper and zinc complexes of calix[4]pyrrole Schiff bases were successfully prepared and their crystal structures were also determined by X-ray diffraction.