Synthesis, crystal structures and characterization of metal–organic framework architectures involving dinuclear copper(ii) benzoic acid derivative complexes

Structural copper(II) complexes with aromatic carboxylic acids show a wide spectrum of coordination schemes. Studies of dicopper(II) carboxylates have been associated with a variety of interests for their catalytic, biological and magnetic applications [1]. Various novel dinuclear copper(II) complexes [Cu2(X-benzoate)4L2] with varying substituents (X = CH3, F, Cl, Br, I, NO2 & OCH3) with a desired octahedral geometry have been synthesized. The various complexes were characterized by single crystal X-ray diffraction studies, spectroscopic and thermal methods (UV/Vis, FTIR and TGA, DSC). In most cases, the structures consists of centrosymmetric dimers in which the Cu atoms show a square pyramidal CuO5 coordination. In all cases, dimeric paddle wheel complexes where two copper(II) ions are held together by four benzoates (forming syn– syn bridges between the copper atoms) and the apical coordination site occupied by a solvent ligand (L) or supramolecular linker were obtained. The dimers are extended into 1D chains that result from hydrogen bonding between the coordinated methanol (solvent ligand) on one Cu(II) and the carboxylate group on an adjacent Cu(II) dimer, including interactions arising from various substituents. π–π Stacking interactions are found to be present in the various crystal structures forming 3D supramolecular array. FTIR and UV/Vis spectra of each complex have shown how the resonance and inductive effect of each substituent affects spectral data of each complex