Electrochemical synthesis and structural studies of zinc(II) complexes with derivatives of benzo[b]furancarboxylic acids

Three novel zinc complexes with benzo[b]furan-carboxylic acids were obtained. The elemental and thermal analyses, and IR spectroscopy were used for basic characterization of compounds. The Zn(II) coordination geometry was studied by X-ray absorption spectroscopy. In microcrystalline powders for all complexes the cation is penta-coordinated (ZnO5) with the Zn–O distances equal to ca. 2 Å, as determined by extended X-ray absorption fine structure. For recrystallized Zn(II) complex 1 (with 7-acetyl-6-methoxy-3-methyl-benzo[b]furan-2-carboxylic acid) crystal structure was determined by X-ray crystallography, and this analysis indicated a distorted polyhedron around the cation in which one of the Zn–O distances is above 2.5 Å.