Controlling the ligating behaviour of biologically important p-hydroxybenzoate towards copper(II) by the use of nitrogen bases: Synthesis, characterization and single crystal X-ray structure determination of [trans-Cu(en)2(H2O)2](L1)2·2H2O and [cis-Cu(L1)2(L2)2] where en=ethylenediamine, L1=p-hydroxybenzoate, L2=3-picoline

Beyond the Simple Copper(II) Coordination Chemistry with Quinaldinate and Secondary Amines

Copper(II) acetate has reacted in methanol with quinaldinic acid (quinoline-2-carboxylic acid) to form [Cu(quin)₂(CH₃OH)]∙CH₃OH (1) (quin⁻ = an anionic form of the acid) with quinaldinates bound in a bidentate chelating manner. In the air, complex 1 gives off methanol and binds water. The conversion was monitored by IR spectroscopy. The aqua complex has shown a facile substitution chemistry with alicyclic secondary amines, pyrrolidine (pyro), and morpholine (morph). trans-[Cu(quin)₂(pyro)₂] (2) and trans-[Cu(quin)₂(morph)₂] (4) were obtained in good yields. The morpholine system has produced a by-product, trans-[Cu(en)₂(H₂O)₂](morphCOO)₂ (5) (morphCOO⁻ = morphylcarbamate), a result of the copper(II) quinaldinate reaction with ethylenediamine (en), an inherent impurity in morpholine, and the amine reaction with carbon dioxide. (pyroH)[Cu(quin)₂Cl] (3) forms on the recrystallization of [Cu(quin)₂(pyro)₂] from dichloromethane, confirming a reaction between amine and the solvent. Similarly, a homologous amine, piperidine (pipe), and dichloromethane produced (pipeH)[Cu(quin)₂Cl] (11). The piperidine system has afforded both mono- and bis-amine complexes, [Cu(quin)₂(pipe)] (6) and trans-[Cu(quin)₂(pipe)₂] (7). The latter also exists in solvated forms, [Cu(quin)₂(pipe)₂]∙CH₃CN (8) and [Cu(quin)₂(pipe)₂]∙CH₃CH₂CN (9). Interestingly, only the piperidine system has experienced a reduction of copper(II). The involvement of amine in the reduction was undoubtedly confirmed by identification of a polycyclic piperidine compound 10, 6,13-di(piperidin-1-yl)dodecahydro-2H,6H-7,14-methanodipyrido[1,2-a:1′,2′-e][1,5]diazocine.

Synthesis, characterization, and in vitro effect of the Cu(II) complex with niflumic acid and 3-picoline on paraoxanase-I

Niflumic acid is used to treat inflammatory rheumatoid diseases, pain, and fever. The present study reports the experimental, spectroscopic, thermal, structural analyses, and biological activities of this complex. The nonsteroidal anti-inflammatory drug niflumic acid, 3-picoline, and copper(II) chloride were utilized to synthesize a new complex: [Cu₂ Cl ₂ (nif) ₂ (3-pic) ₄ ]. The crystal structure of [Cu ₂ Cl ₂ (nif) ₂ (3-pic) ₄ ] was determined by X-ray crystallography. The complex crystallizes in the triclinic space group P-1 and each Cu(II) center displayed six-coordinated distorted octahedral geometry. Two Cu(II) centers are connected by a chloro-bridge to form the binuclear metal core. Finally, the in vitro effects of the synthesized new complex and free niflumic acid were evaluated on the human serum paraoxonase 1 enzyme. At low doses, both the new complex and free niflumic acid showed very good inhibition activity with different inhibition mechanisms. In addition, the results showed that the new complex has more inhibition activity than free niflumic acid.

Modulatingp-hydroxycinnamate behavior as a ditopic linker or photoacid in copper(ii) complexes with an auxiliary pyridine ligand

p-Hydroxycinnamate behaves either as a ditopic linker or as a photoacid in copper(ii) complexes with a suitable auxiliary pyridine ligand.

Four monomeric copper(ii) complexes of non-steroidal anti-inflammatory drug Ibuprofen and N-donor ligands: syntheses, characterization, crystal structures and cytotoxicity studies

The cytotoxic effects of four new Ibuprofen–Cu(ii) complexes were tested finding significant cytotoxicity on human melanoma cell line HT-144.

Structure, EPR/ENDOR and DFT characterisation of a [Cu(II)(en)2](OTf)2 complex

The Jahn-Teller distorted Cu(II) complex [Cu(en)2](OTf)2 1 (en = 1,2-diaminoethane) has been reported and characterised using X-ray crystallography, EPR and ENDOR spectroscopy, and DFT calculations. The solid state structure shows an intra- and inter-molecular hydrogen-bonded network via the N-H groups and the coordinated triflate anions. CW and pulsed EPR/ENDOR were used to determine the spin Hamiltonian parameters of the Cu(II) complex, which were in excellent agreement with the DFT. The structure of the complex, as determined by angular selective ENDOR, is also in good agreement with the crystal structure, confirming the axial coordination of the counter-ion(s) in the frozen solution. The small (14)N superhyperfine couplings are also consistent with the sp(3) hybridised nature of the coordinating nitrogens. These results show that the correlation between the (14)N hyperfine coupling and hybridisation of donor nitrogens can be useful to determine not only the coordination around the Cu(ii) metal centre but also the nature of the donor in unknown Cu(II) systems.

Bis(4-hy-droxy-benzoato-κO,O')bis-(pyridine-κN)copper(II)

In the title compound, [Cu(C₇H₅O₃)₂(C₅H₅N)₂], the Cu atom is located on an inversion center and is coordinated by the N atoms of the two pyridine ligands, trans to each other, and to the carboxyl­ate O atoms of two bidentate 4-hy­droxy­benzoate ligands [Cu—O = 1.9706 (10) and 2.5204 (11) Å]. Hydrogen bonding between hy­droxy H and carboxyl­ate O atoms results in a layer structure parallel to the ab plane.