Comparison of the synthesis of meta- and para-substituted heterocyclic ligands for complexation with metals. Study of the resulting complexes by X-ray crystallography

Abstract

Organic compounds with conjugated azo groups (-N=N-) allow reversible isomerization between the cis and trans isomers under UV irradiation. As a consequence of this isomerization, there are changes in the physicochemical properties of the compounds such as their refractive indices, dielectric constants, redox potentials and their geometric structures. This characteristic makes such azo compounds interesting in fields of study such as the development of liquid crystals, photo switches,(1) or even as therapeutic agents and drug delivery systems.(2) Our research group is interested in the synthesis of new ligands incorporating azo and imine groups capable of coordinating with metal cations (especially with lanthanides) in order to obtain new nanomaterials that have the properties of single-molecule magnets (SMM) in which irradiation with UV light can modulate their properties. This report is a continuation of previous work carried out in our group and addresses the synthesis of a meta-substituted ligand that provides an interesting structure for coordination with metal cations. The synthesis of analogous para-substituted ligands was also carried out for comparison purposes Furthermore, studies of the crystal structure of both the free-ligands and those coordinated with metal cations were carried out by X-ray crystallography.