Tetrakis(μ-2-phenylquinoline-4-carboxylato-κ2 O:O′)bis[(methanol-κO)copper(II)]

The title complex, [Cu2(C16H10NO2)4(CH3OH)2], consists of centrosymmetric wheel-shaped dinuclear neutral molecules in which each CuII atom is coordinated in a slightly distorted square-pyramidal geometry by four O atoms of carboxylate groups from different ligands at the basal plane and an O atom of a methanol molecule at the axial position. In the crystal, the dinuclear complex molecules are linked into one-dimensional supramolecular columns parallel to the b axis by O—H⋯N hydrogen bonds and π–π stacking interactions [centroid–centroid distance = 3.7259 (11) Å].

The title complex, [Cu 2 (C 16 H 10 NO 2 ) 4 (CH 3 OH) 2 ], consists of centrosymmetric wheel-shaped dinuclear neutral molecules in which each Cu II atom is coordinated in a slightly distorted square-pyramidal geometry by four O atoms of carboxylate groups from different ligands at the basal plane and an O atom of a methanol molecule at the axial position. In the crystal, the dinuclear complex molecules are linked into one-dimensional supramolecular columns parallel to the b axis by O-HÁ Á ÁN hydrogen bonds andstacking interactions [centroidcentroid distance = 3.7259 (11) Å ].
The title complex shows a dinuclear paddle-wheel unit [Cu 2 (L) 4 (CH 3 OH) 2 ] (Fig. 1), which is composed of two copper(II) ions, four L ligands and two methanol molecules. Each metal is pentacoordinated by four O atoms of the carboxylate groups from different ligands [Cu-O mean length = 1.961 (3) Å] at the equatorial plane and one O atom of a CH 3 OH molecule at the axial position. One of the most common parameters used to define the coordination geometry of a pentacoordinated metal center, the τ index, is 0.0003, indicating an almost-ideal square-pyramidal coordination. The metal ion deviates from the mean equatorial plane of the square pyramid toward the apical O5 atom by 0.1942 (3) Å. The Cu···Cu distance is 2.6303 (5) Å, which is within the normal range observed for dinuclear paddle-wheel units in the structures of copper(II) carboxylate complexes (Bu et al., 2005;Wang et al., 2010;Ma & Lin, 2008). In the crystal (Fig. 2), the dinuclear complex molecules are linked into one-dimensional columns parallel to the b axis through intermolecular O-H···N hydrogen bonds (Table 1) and π-π stacking interactions involving adjacent quinoline rings, with centroid-centroid distances of 3.7259 (11) Å and perpendicular interplanar separations of 3.4838 (8) Å.

Refinement
All H atoms were placed in idealized positions and allowed to ride on their parent atoms, with C-H = 0.93-0.96 Å and O-H = 0.83 Å, and with U iso (H) = 1.5U eq (C,O) for methyl and hydroxy H atoms and 1.2U eq (C) otherwise.

Figure 1
The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level.
Unlabelled atoms are related to labelled atoms by the symmetry code (-x+1, -y, -z+1).  Partial crystal packing of the title compound, showing the formation of a columnar supramolecular structure through hydrogen bonds (dashed lines).

Tetrakis(µ-2-phenylquinoline-4-carboxylato-κ 2 O:O′)bis[(methanol-κO)copper(II)]
Crystal data Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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.