Ferromagnetic coupling in a unique Cu(II) metallacyclophane with functionalized diazamesocyclic ligands formed by Cu(II)-directed self-assembly: magneto-structural correlations for dichloro-bridged Cu(II) dinuclear complexes

Abstract

Two new di-μ-Cl dinuclear Cu^II complexes [Cu(HL¹)Cl₂]₂(ClO₄)₂ (1) and [Cu₂(L²)₂Cl₂](ClO₄)₂ (2) with the pyridyl-functionalized diazamesocyclic ligands 1,5-bis(pyridin-4-ylmethyl)-1,5-diazacyclooctane (L¹) and 1-(pyridin-2-ylmethyl)-1,4-diazacycloheptane (L²) have been synthesized and structurally characterized by single crystal X-ray diffraction. Complex 1 is a unique paramagnetic Cu^II metallamacrocycle (ca. 14.1 × 3.5 Ų) directly self-assembled by metal ions and the organic spacer under strongly acidic conditions. The magnetic properties of both complexes have been investigated by variable-temperature magnetic susceptibility measurements. Although complexes 1 and 2 have almost the same geometrical parameters for Cu^II, their magnetic parameters vary from ferromagnetic for 1 to antiferromagnetic for 2. The magneto-structural correlation of such complexes has been further developed.