Mononuclear and binuclear copper(II) complexes with bis(2-imidazolyl)(bis(methoxycarbonyl)methylmethane) (BIBM), a tripodal bis(imidazole) based ligand. Synthesis, crystal structure and magnetic Characterization of [Cu(BIBM)2](ClO4)2 and [{Cu(BIBM)(H2O)}2

Two new Cu(II) complexes with bis(2-imidazolyl) (bis(methoxycarbonyl)methylmethane) (BIBM), a tridentate bis(imidazole) based ligand with the formula [Cu(BIBM)2](ClO4)2 (1) and [{Cu(BIBM)(H2O)}2(μ1,2,3,4-C2O4)](C4O4)·6H2O (2) have been synthesized and characterized. Compound 1 shows mononuclear cationic [Cu(BIBM)2]2+ units and perchlorate ions. The coordination around the Cu(II) ion shows a tetragonally-elongated octahedral geometry. The BIBM ligand acts as a k3-N,N’,O tripodal ligand, through two imidazole N atoms and a weak Cu–O(carboxymethyl) axial interaction. In the crystal structure cations and anions connect through H-bonds generating linear chains. Linear chains assemble forming molecular layers through imidazole rings aromatic–aromatic interactions. The structure of compound 2 consists on centrosymmetric oxalate-bridged binuclear [Cu2(BIBM)2(OH2)2(μ1,2,3,4-C2O4)]2+ units, squarate dianions and water molecules in a 1:1:6 relation. The geometry around copper ions could be described as tetragonally elongated octahedrons of the 4+1+1′ type. In the structure, molecular building blocks (MBBs) are packed together by multiple-path H-bonding and π–π stacking interactions, giving rise to the supramolecular 3D network. The molecular EPR spectra is indicative of an essentially dx2-y2dx2-y2 ground state for copper(II) ions in both compounds. Magnetic susceptibility measurements of compound 2 show strong antiferromagnetic exchange between the copper(II) ions (J = −325 cm−1). The magnitude of the exchange interaction is discussed in relation to the structural features and compared with published magneto-structural data on similar oxalato-bridged copper(II) compounds.

Graphical abstractThe synthesis, crystal structure and magnetic characterization of two new Cu(II) complexes with a bis(imidazole) based molecule which acts as a k3-N,N′,O tripodal ligand. In both mononuclear and dinuclear compounds the building blocks (MBBs) are packed together by multiple-path H-bonding and π–π stacking interactions.Magnetic susceptibility measurements of the dinuclear compound show strong antiferromagnetic exchange between the copper(II) ions through the oxalato bridge. This behaviour is discussed in relation to the structural features and compared with published magneto–structural data on similar oxalato-bridged copper(II) compounds.Figure optionsDownload full-size imageDownload as PowerPoint slide