Synthesis and spectroscopic characterization of dicyanamido–Cu(II) complexes. Part 21: Crystal structure of the complexes of tris[2-(2-pyridylethyl)]amine, tris(2-pyridylmethyl)amine and 1,4-bis[2-(2-pyridylethyl)]piperazine

Two classes of novel dicyanamido (dca)–Cu(II) complexes were synthesized with a variety of tetradentate tripod amines, tridentate amines and diazacycloalkanes with pyridyl arms of different alkyl lengths and with tetra-aza macrocycles with different cavity sizes; the mononuclear, Cu(L)(dca)]ClO4 (L = tepa (1), TPA (2), pzdepy (4), hpzpy2 (5), cyclen (7), cyclam (8), tacp (9)) or Cu(L)(dca)ClO4 (L = MeDPA (10), Mepea (11)) and the dinuclear, [Cu2(L′)2(dca)](ClO4)3 (L′ = pmap (3), pzpy2 (6)). The isolated complexes were structurally characterized by electronic and IR spectroscopy as well as by X-ray. Single crystal X-ray diffraction analysis of the complexes [Cu(tepa)(dca)]ClO4 (1), [Cu(TPA)(dca)]ClO4 (2) and [Cu(pzdepy)(dca)]ClO4 (4) reveal their monomeric penta-coordinate nature with the isolated [Cu(L)(dca)]+ cations and ClO4− counter ions. All the complexes with the exception of 2 adapt distorted square pyramidal geometry while the coordination polyhedron around the copper center in 2 may be described as a distorted trigonal bipyramidal stereochemistry. The visible spectra of the complexes in aqueous solutions or in methanol are in complete agreement with the assigned X-ray geometry around the Cu(II) centers.