Crystal structure of a mononuclear copper(II) complex with 2-methoxy-N,N-bis-(quinolin-2-yl-meth-yl)-ethyl-amine...

Structural characterization of the compound [Cu(C₂H₃N)(C₂₃H₂₃N₃O)](ClO₄)₂] or [Cu(C₂H₃N)(DQMEA)](ClO₄)₂] [DQMEA = 2-methoxy-N,N-bis-(quinolin-2-ylmeth-yl)ethyl-amine] {systematic name: (aceto-nitrile)[2-methoxy-N,N-bis(quinolin-2-ylmeth-yl)ethyl-amine]-copper(II) diperchlorate} by single-crystal X-ray diffraction reveals a complex cation with a tetra-dentate coordination of the DQMEA ligand along with monodentate coordination of a CH₃CN ligand to a single Cu^II center, with two perchlorate anions providing charge balance. The Cu^II center has a distorted square-pyramidal geometry in which the nitro-gen atoms of the DQMEA and CH₃CN ligands occupy the equatorial positions, while the oxygen atom of the DQMEA ligand resides in the axial position with an elongated Cu-O bond. The quinoline ring systems are nearly co-planar in the structure, while the linear CH₃CN ligand is tilted significantly below this plane, and the central nitro-gen of DQMEA is above it. Within the complex, weak C-H⋯N hydrogen bonding takes place between the nitro-gen of CH₃CN and a neighboring quinolyl group. The perchlorate ions are disordered within the structure, but undergo a number of weak inter-molecular C-H⋯O hydrogen-bonding inter-actions. Additional weak π-stacking inter-actions between the quinolyl groups of neighboring complexes further stabilize the crystal packing.