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

The title tridentate ligand, C(14)H(10)N(4)O, N-(quinolin-8-yl)pyrazine-2-carboxamide (HL1), crystallizes with three independent mol-ecules (A, B and C) in the asymmetric unit. All three mol-ecules are relatively planar (r.m.s. deviations are 0.068, 0.055 and 0.06†à , 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)†à ], forming layers parallel to the ab plane. The title complex, [Cu(4)(C(42)H(44)N(8)O(16))]·2CH(3)OH, {hexa-μ-acetato-1:2κ(2) O:O';2:3κ(8) O:O';3:4κ(2) O:O'-di-methanol-1κO,2κO-bis-[N-(quinolin-8-yl)pyrazine-2-carboxamide]-1κ(3) N,N',N'';4κ(3) N,N',N''-tetra-copper(II) methanol disolvate} (I), was obtained by the reaction of HL1 with Cu(CH(3)CO(2))(2). It consists of a tetra-nuclear complex with a central tetra-kis-(μ-acetato)-dicopper paddle-wheel moiety linked on either side via bridging acetato ions to a mononuclear copper(II)-(L1) 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)†à ] and C-H⋯O hydrogen bonds, leading to the formation of a supra-molecular framework.