Syntheses and crystal structures of a new pyrazine dicarboxamide ligand, N (2),N (3)-bis-(quinolin-8-yl)pyrazine-2,3-dicarboxamide, and of a copper perchlorate binuclear complex.

The title pyrazine dicarboxamide ligand, N (2),N (3)-bis-(quinolin-8-yl)pyrazine-2,3-dicarboxamide (H(2)L1), C(24)H(16)N(6)O(2), has a twisted conformation with the outer quinoline groups being inclined to the central pyrazine ring by 9.00†(6) and 78.67†(5)°, and by 79.94†(4)° to each other. In the crystal, molecules are linked by C-H⋯O hydrogen bonds, forming layers parallel to the (10) plane, which are in turn linked by offset π-π inter-actions [inter-centroid distances 3.4779†(9) and 3.6526†(8)†à ], forming a supra-molecular three-dimensional structure. Reaction of the ligand H(2)L1 with Cu(ClO(4))(2) in aceto-nitrile leads to the formation of the binuclear complex, [μ-(3-{hy-droxy[(quinolin-8-yl)imino]-meth-yl}pyrazin-2-yl)[(quinolin-8-yl)imino]-methano-lato]bis-[diaceto-nitrile-copper(II)] tris-(per-chlor-ate) aceto-nitrile disolvate, [Cu(2)(C(24)H(15)N(6)O(2))(CH(3)CN)(4)](ClO(4))(3)·2CH(3)CN or [Cu(2)(HL1(-))(CH(3)CN)(4)](ClO(4))(3)·2CH(3)CN (I). In the cation of complex I, the ligand coordinates to the copper(II) atoms in a bis-tridentate fashion. A resonance-assisted O-H⋯O hydrogen bond is present in the ligand; the position of this H atom was located in a difference-Fourier map. Both copper(II) atoms are fivefold coordinate, being ligated by three N atoms of the ligand and by the N atoms of two aceto-nitrile mol-ecules. The first copper atom has a perfect square-pyramidal geometry while the second copper atom has a distorted shape. In the crystal, the cation and perchlorate anions are linked by a number of C-H⋯O hydrogen bonds, forming a supra-molecular three-dimensional structure.