A pyrazole-based orthogonal ferromagnetically coupled [2×2] homoleptic square Cu4 grid: Magnetostructural correlations

Coordination polymer of copper with a silicon-containing Schiff base

A Schiff base was prepared by condensation reaction of 2,6-diformyl-4-methylphenol with trimethylsilyl-methyl- p-aminobenzoate and it was further used, without isolation, as a ligand for copper (Cu(II)) ions. The structure of the resulting coordination complex was evidenced by spectral techniques (Fourier transform infrared spectroscopy, nuclear magnetic resonance and ultraviolet-visible spectroscopy) and by single crystal X-ray diffraction, which revealed a covalent one-dimensional (1D) structure where neutral molecular units (Cu(II) coordination polymer [CuL2]) are linked through the bridging oxygen atoms. The 1D polymeric chains are associated by intermolecular C–H···O hydrogen bonding to form two-dimensional supramolecular layers. The polymeric nature of the compound was also supported by the presence of glass transition in differential scanning calorimetry trace. This coordination polymer forms spherical aggregates in a nonpolar medium (hexane) as was emphasized by transmission electron microscopy image taken on the film remained after solvent evaporation. The thermogravimetrical analysis indicates a good stability for the Cu(II) coordination polymer and the biological tests revealed good antibacterial and antifungal activities.

3-Acetyl-1-(3-methylphenyl)-5-phenyl-1H-pyrazole-4-carbonitrile

In the title compound, C₁₉H₁₅N₃O, the central pyrazole ring makes dihedral angles of 35.52 (12) and 62.21 (11)° with the attached phenyl and methyl-substituted phenyl rings, respectively. The corresponding angle between the phenyl and methyl-substituted phenyl rings is 62.90 (11)°. In the crystal, mol­ecules are connected by weak C—H⋯O hydrogen bonds, forming supra­molecular chains propagating along the a-axis direction.

1-{3-[1-(Hydroxyimino)ethyl]-4-methyl-1H-pyrazol-5-yl}ethanone

In the title compound, C(8)H(11)N(3)O(2), the oxime and the acetyl groups adopt a transoid conformation, while the pyrazole H atom is localized in the proximity of the acetyl group and is cis with respect to the acetyl O atom. In the crystal, dimers are formed as the result of hydrogen-bonding inter-actions involving the pyrazole NH group of one mol-ecule and the carbonyl O atom of another. The dimers are associated into sheets via O-H⋯N hydrogen bonds involving the oxime hydroxyl and the unprotonated pyrazole N atom, generating a macrocyclic motif with six mol-ecules.

A 'Butterfly'-shaped Water Tetramer in a Cu4 Complex Supported by a Hydrazone Ligand: Synthesis, Crystal Structure, Magnetic Properties, and Quantum Chemical Study

A potentially tetradentate NOOO donor hydrazone ligand, LH2 (condensation product of benzhydrazide with O-vanillin) generates a tetranuclear CuII complex [Cu4(L)4]·4H2O (1), whose void spaces are occupied by water tetramers presenting a ‘butterfly’ conformation with the highest dihedral angle reported to date, as revealed by its X-ray crystal structure. 1 has also been characterized using various spectroscopic techniques, including IR, UV-vis, and elemental analysis. Variable temperature magnetic susceptibility measurements reveal the presence of moderate antiferromagnetic intra-tetramer coupling between the four CuII centres connected through simple oxo groups of the hydrazone ligand with two different coupling constants (J1 = –61.7(3) cm–1 and J2 = –92(1) cm–1) corresponding to the two different CuII tetramers identified in the X-ray structure. We also report a quantum chemical study (MP2(full)/6–311+G(3df,2p)//B3LYP/6–311+G(3df,2p)) to calculate the stability of the water tetramers.