Methanoldinitrato[N-(2-pyridylmethylene)aniline]copper(II)

The Cu atom in the title compound, [Cu(NO3)2(C12H10N2)(CH3OH)], adopts a square-pyramidal geometry, being ligated by two N atoms of the bidentate N-(2-pyridylmethylene)aniline (ppma) ligand, two O atoms of NO3 ligands and one O atom of a methanol molecule, which occupies the apical position. The phenyl ring on the ppma ligand is twisted out of the pyridine plane, forming a dihedral angle of 42.9 (1)°. In the crystal, intermolecular O—H⋯O hydrogen bonds between methanol and NO3 ligands form an extensive one-dimensional network extending parallel to [100].


Comment
Schiff base complexes of transition metal complexes have great importance over the years due to their versatility of the steric and electronic properties and their possible applications as molecular based magnetic materials (Lu et al., 2007;Mukherjee et al., 2008;Tao et al., 2004). As a part of this research, we reported copper halides complexes with N2 bidentate Schiff base ligand derived from 2-pyridinecarboxylaldehyde and benzylamine (Lee et al., 2008), in which the reaction of copper(II) chloride leads to a dimeric complex whereas copper(II) bromide affords a monomeric copper complex. In this study, we reacted copper(II) nitrate with the similar Schiff base in methanol and prepared a monomeric penta-coordinated copper(II) complex, Cu(ppma)(NO 3 ) 2 (CH 3 OH) (I).
In the title compound, the Cu atom adopts a square pyramidal geometry, being ligated by two N atoms of the bidentate N-(2-pyridylmethylene)aniline (ppma) ligand, two O atoms of NO3 ligands, and one O atom of methanol which occupies the apical position. The angles around Cu atom at the basal position are in the range of 80.8 (1) -96.6 (1)°. The calculated trigonality index, τ = 0.12, indicates that the Cu atom is in an almost square pyramidal geometry (Addison et al., 1984).
The phenyl ring on the ppma ligand is twisted out of the pyridine plane, and forms a dihedral angle of 42.9 (1) °. The intermolecular O23-H23-O18 i [symmetry code: (i) x -1/2, -y + 3/2, -z] hydrogen bond allows to form an extensive one-dimensional network, which stabilizes the crystal structure.
EPR (electron paramagnetic resonance) spectra of I compound were obtained both for solid and for frozen glass samples (toluene/methanol) at 77 K. The powder EPR spectrum exhibits isotropic feature, <g>=2.151. The solution EPR spectrum exhibits well defined hyperfine structure with parallel and perpendicular components, g(parallel) = 2.328, g(perpendicular) = 2.065 and A(parallel) =142x10 -4 cm -1 , typically indicating a d x

2
-y 2 ground state, g(parallel) > g(perpendicular) > 2.0023 (Mohapatra et al., 2008). The magnetic susceptibilities of the title compound were collected as a function of temperatures (4 -300 K). The magnetic susceptibility data increases as the temperatures decrease exhibiting a paramagnetic behavior.
Magnetic susceptibility data follows the Curie-Weiss law showing the features of a discrete monomeric complex. A linear regression results in a Curie-Weiss temperature θ = 0.55 K and a Curie constant C = 0.45 cm 3 K mol -1 .
Experimental N-(2-pyridylmethylene)aniline was synthesized from the direct reaction of 2-pyridinecarboxyaldehyde and aniline. 2-Pyridinecarboxyaldehyde (2 mmol) dissolved in 20 ml of absolute methanol was added dropwise to a methanolic solution of aniline (2 mmol) and then refluxed overnight. After cooling to room temperature, a solution of Cu(NO 3 ) 2 3H 2 O (2 mmol) in 20 ml of absolute methanol was added to the mixed solution of 2-pyridinecarboxyaldehyde and aniline (ppma solution).
The solution was changed to dark green color immediately. The resulting solution was allowed to stand at room temperature.
The green crystals were obtained by slow evaporation in methanol.

Refinement
The H23 atom was located in a difference map and refined freely with O-H = 0.69 (3) Å. Other H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93 -0.96 Å, and with U iso (H) = 1.2U eq (C) for aromatic and 1.5U eq (C) for methyl H atoms. Fig. 1. Molecular structure of (I), showing the atom-numbering scheme and 30% probability ellipsoids.