Abstract
The title pyrazine dicarboxamide ligand, N 2,N 3-bis-(quinolin-8-yl)pyrazine-2,3-dicarboxamide (H2L1), C24H16N6O2, 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) Å], forming a supra-molecular three-dimensional structure. Reaction of the ligand H2L1 with Cu(ClO4)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, [Cu2(C24H15N6O2)(CH3CN)4](ClO4)3·2CH3CN or [Cu2(HL1-)(CH3CN)4](ClO4)3·2CH3CN (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.
Highlights
The title pyrazine dicarboxamide ligand, N2,N3-bis(quinolin-8-yl)pyrazine-2,3dicarboxamide (H2L1), C24H16N6O2, 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
Molecules are linked by C—HÁ Á ÁO hydrogen bonds, forming layers parallel to the (101) plane, which are in turn linked by offset – interactions [intercentroid distances 3.4779 (9) and 3.6526 (8) A ], forming a supramolecular three-dimensional structure
We report on the syntheses and crystal structures of the title pyrazine dicarboxamide ligand (H2L1), and of a binuclear copper complex, I, which was synthesized
Summary
The title ligand, N2,N3-bis(quinolin-8-yl)pyrazine-2,3-dicarboxamide (H2L1), is very similar to ligand N2-[(2,3-dihydropyridin-2-yl)methyl]-N3-(pyridin-2-ylmethyl)pyrazine-2,3-dicarboxamide (H2L2), for which two polymorphs have been reported (Cati et al, 2004; Cati & Stoeckli-Evans, 2004) These and other pyrazine-carboxamide ligands were synthesized to explore their coordination behaviour with first-row transition metals and to study the magnetic exchange behaviour of the complexes (Cati, 2002). With ligand H2L2, grid [2 Â 2] complexes have been synthesized using Cu(BF4) (Hausmann et al, 2003), and with Cu(ClO4) and NiCl2 (Cati et al, 2004) The latter complexes were shown to exhibit multiple anion encapsulation and antiferromagnetic exchange behaviour. On the opposite side of the molecule, the quinoline ring system (N6/C16–C124, r.m.s. deviation 0.009 A ) is inclined to the pyrazine ring by 78.67 (5), with a single intramolecular N—HÁ Á ÁN contact (Fig. 1, Table 1). The intramolecular contacts are shown as dashed lines (see Table 1)
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