5,5-Diethylbarbiturato complexes of copper(II) with (2-aminoethyl)piperidine, -pyrrolidine,and -morpholine: syntheses,crystal structures,spectroscopic, and thermal properties

Three new complexes, [Cu(barb)₂(aepip)] · 0.5H₂O (1), [Cu(barb)₂(aepyrd)] (2), and [Cu(barb)₂(aemrph)] (3), have been synthesized by reaction of 5,5-diethlybarbiturate anion (barb) with copper(II) in the presence of (2-aminoethyl)piperidine (aepip), -pyrrolidine (aepyrd), and -morpholine (aemrph). All complexes were characterized by elemental analysis, spectroscopic (IR and UV/Vis), thermal (DTA-TGA), and magnetic susceptibility measurements. X-ray single crystal diffraction shows that 1 and 2 are discrete mononuclear species, in which copper(II) is coordinated by two bidentate barb ligands and a chelating aepip or aepyrd, forming a square-pyramidal coordination geometry. Complexes 1 and 2 show unequal coordination of barb, one N-coordinate, and one bidentate. Complex 3 is also mononuclear, but copper(II) is square-planar with two N-coordinated barb and one bidentate aemorph. Molecules of 1–3 are bridged by strong hydrogen bonds to generate 1-D or 2-D supramolecular networks. Spectral and thermal data for 1–3 are in agreement with crystal structures.