The crystal structures of the ligand -(quinolin-8-yl)pyrazine-2-carboxamide and of a tetra-nuclear copper(II) complex.

The title tridentate ligand, CHNO, -(quinolin-8-yl)pyrazine-2-carboxamide (), crystallizes with three independent mol-ecules (, and ) in the asymmetric unit. All three mol-ecules are relatively planar (r.m.s. deviations are 0.068, 0.055 and 0.06 Å, respectively), with the NH H atom forming three-centered (bifurcated) intra-molecular N-H⋯N hydrogen bonds in each mol-ecule. There is also an intra-molecular C-H⋯O contact present in each mol-ecule, involving the benzene ring of the quinoline unit and the amide carboxamide O atom. In the crystal, the three mol-ecules stack in columns with the various mol-ecules being linked by offset π-π inter-actions [inter-centroid distances vary from 3.367 (5) to 3.589 (5) Å], forming layers parallel to the plane. The title complex, [Cu(CHNO)]·2CHOH, {hexa-μ-acetato-1:2κ :';2:3κ :';3:4κ :'-di-methanol-1κ,2κ-bis-[-(quinolin-8-yl)pyrazine-2-carboxamide]-1κ ,','';4κ ,',''-tetra-copper(II) methanol disolvate} (), was obtained by the reaction of with Cu(CHCO). It consists of a tetra-nuclear complex with a central tetra-kis-(μ-acetato)-dicopper paddle-wheel moiety linked on either side bridging acetato ions to a mononuclear copper(II)-() complex; it crystallizes as a methanol disolvate. The complex possesses inversion symmetry, being located about a center of symmetry situated at the mid-point of the Cu⋯Cu bond of the paddle-wheel moiety. In the crystal, the complex mol-ecules are linked by O-H⋯O hydrogen bonds, forming chains along the [01] direction, which are linked by offset π-π inter-actions [inter-centroid distance = 3.7367 (11) Å] and C-H⋯O hydrogen bonds, leading to the formation of a supra-molecular framework.