Bis(cinnamato-κO)(1,10-phenanthroline-κ2 N,N′)copper(II)

The title mononuclear CuII complex, [Cu(C9H7O2)2(C12H8N2)], is comprised of a CuII cation, two cinnamate (L −) ligands and a 1,10-phenanthroline (phen) ligand. The CuII atom and phen ligand lie on a twofold rotation axis. The CuII atom is coordinated by two O atoms from two carboxylate groups of two (L −) ligands and two N atoms from one phen ligand, exhibiting a distorted square-planar geometry. In the crystal, molecules are assembled into supramolecular chains parallel to the c axis through weak C—H⋯O hydrogen bonds involving the phen and cinnamate ligands.


Related literature
1,10-Phenanthroline is of great interest in the field of supramolecular chemistry as it can form C-HÁ Á ÁO or C-HÁ Á ÁN hydrogen bonds andstacking interactions (Liu et al., 2004;Wang et al., 2003), which can effectively result in one-dimensional or two-dimensional networks.

Comment
The mononuclear metal complexes of the chelating bidentate 1,10-phenanthroline (phen) and 2,2′-bipyridine (bipy) ligands are well known in the literature, and have been used in many fields. In the realm of coordination polymers, these complexes have been employed as coordination acceptor nodes for the construction of low dimensional polymer-based magnets exhibiting long-range magnetic ordering and spin crossover transitions. 1,10-Phenanthroline is of great interest in the field of supramolecular chemistry, because it can bring C-H···O or C-H···N hydrogen bonds and π-π stacking interactions (Liu et al., 2004 andWang et al., 2003), which can effectively result in one-dimensional or two-dimensional networks. We report here the preparation and crystal structure of the title compound,[Cu(C 9 H 7 O 2 ) 2 (C 12 H 8 N 2 )].
The asymmetric unit contains a half Cu II cation, a half phen ligand and one cinnamic ligand (L -: C 6 H 5 -CH=CH-COO -).
The Cu II atom lies on a twofold rotation axis. In the complex, two equivalent Lanions function as monodentate ligands, while one phen molecule functions as a terminal ligand adopting the expected chelating mode to coordinate with one Cu II ion, forming a mononuclear unit. The Cu II ion is coordinated by two O atoms (O1, O1 i , symmetry code (i): -x, y, -z + 1/2) from two cinnamic ligands, two N atoms (N1,N1 i ) from 1,10-phenanthroline molecules, exhibiting essentially distorted square planar geometry (Fig. 1). The Cu-N/O bonds distances are 2.018 (3) Å and 1.948 (3) Å, respectively. The carboxylate group shows a distortion from the molecular plane; the dihedral angle between the mean-plane (C3-C9) and the carboxlate group (O1/C1/O2) is 25.8 (4)°. The two carboxylate groups are almost perpendicular to one another with a dihedral angle of 78.9 (6)°.
In the crystal, molecules are assembled into one dimensional supramolecular chains parallel to the c axis through weak C-H···O hydrogen bonds involving the phen and carboxylate ligands (Table 1, Fig. 2).

Experimental
A methanol solution (5 ml) of phen (0.046 mg, 0.25 mmol) and cinnamic acid (0.07 mg, 0.5 mmol) were added dropwise to a methanol solution of (5 ml) CuSO 4 .5H 2 O (0.058 mg, 0.25 mmol) with constant stirring during 1 h. The mixture was then filtered and the filtrate allowed to stand for 10 days, after which small blue block-like crystals of the title complex were obtained.

Refinement
The C-bound hydrogen atoms were placed in geometrically idealized positions and constrained to ride on their parent atom positions with a C-H distances of 0.93 Å and with U iso (H) = 1.2Ueq(C).

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq