The Crystal Structure of a Novel Copper(II) Complex with Asymmetric Ligand Derived from l-Histidine

The crystal structure of a novel copper(II) complex with a potentially
hexadentate Schiff base ligand derived from l-histidine has been
solved by a single-crystal X-ray diffraction method at pH 7.4. The
copper(II) ion is coordinated asymmetrically by a tetradentate ligand
with the amino and imidazole imido nitrogen atoms on one side
versus imino nitrogen and carboxylate oxygen atoms on the other
side in a distorted square-planar geometry. The formation of an
infinite chain through carboxylate coordination is observed. The
novel ligand is obtained by the reaction between the l-histidine
molecules coordinated to copper(II) and 4-hydroxy-4-methylpentan-2-one formed by aldol condensation of acetone. This complex
provides insights into a possible structural arrangement between
copper(II) and l-histidine which is physiologically important and
abundantly present in biological systems.