Structural and first magnetic characterization of unique mono-μ-chloro bridged dinuclear CuII complexes with heterocycle-functionalized diazamesocyclic ligands

Abstract

Two new diazamesocyclic ligands based on 1,4-diazacycloheptane (DACH), functionalized by additional heterocyclic donor groups, 1,4-bis(pyridin-2-ylmethyl)-1,4-diazacycloheptane (L¹) and 1,4-bis(imidazol-4-ylmethyl)-1,4-diazacycloheptane (L²), together with their Cu^II complexes [Cu₂(μ-Cl)(L¹)₂](ClO₄)₃ (1) and [Cu₂(μ-Cl)(L²)₂](ClO₄)₃ (2), have been synthesized and characterized. Single crystal X-ray diffraction analyses revealed that both complexes have the unique mono-μ-Cl dimeric [Cu₂(μ-Cl)(L)₂]³⁺ structural motif. For both complexes, each Cu^II center is penta-coordinate in a distorted square-pyramidal environment with the bridging chloride atom at the apical position. The magnetic properties of mono-μ-chloro Cu^II dinuclear complexes have been investigated for the first time through the study of complexes 1 and 2 by variable temperature magnetic susceptibility and magnetization measurements. Weak ferromagnetic (for 1) or anti-ferromagnetic (for 2) interactions between the two Cu^II centers have been found and possible magneto-structural correlations have been analyzed.