Recently Reported Biological Activities and Action Targets of Pt(II)- and Cu(II)-Based Complexes.

Most diseases that affect human beings across the world are now treated with drugs of organic origin. However, some of these are associated with side effects, toxicity, and resistance phenomena. For the treatment of many illnesses, the development of new molecules with pharmacological potential is now an urgent matter. The biological activities of metal complexes have been reported to have antitumor, antimicrobial, anti-inflammatory, anti-infective and antiparasitic effects, amongst others. Metal complexes are effective because they possess unique properties. For example, the complex entity possesses the effective biological activity, then the formation of coordination bonds between the metal ions and ligands is controlled, metal ions provide it with extraordinary mechanisms of action because of characteristics such as d-orbitals, oxidation states, and specific orientations; metal complexes also exhibit good stability and good physicochemical properties such as water solubility. Platinum is a transition metal widely used in the design of drugs with antineoplastic activities; however, platinum is associated with side effects which have made it necessary to search for, and design, novel complexes based on other metals. Copper is a biometal which is found in living systems; it is now used in the design of metal complexes with biological activities that have demonstrated antitumoral, antimicrobial and anti-inflammatory effects, amongst others. In this review, we consider the open horizons of Cu(II)- and Pt(II)-based complexes, new trends in their design, their synthesis, their biological activities and their targets of action.

Synthesis and Characterization of a New Cu(II) Paddle-Wheel-like Complex with 4-Vinylbenzoate as an Inorganic Node for Metal-Organic Framework Material Design.

A new Cu(II) paddle-wheel-like complex with 4-vinylbenzoate was synthesized using acetonitrile as the solvent. The complex was characterized by X-ray crystal diffraction, FT-IR, diffuse reflectance spectroscopy, thermogravimetric, differential scanning calorimetric, magnetic susceptibility, and electronic paramagnetic resonance analyses. The X-ray crystal diffraction analysis indicated that each copper ion was bound at an equatorial position to four oxygen atoms from the carboxylate groups of the 4-vinylbenzoate ligand in a square-based pyramidal geometry. The distance between the copper ions was 2.640(9) Å. The acetonitrile molecules were coordinated at the axial position to the copper ions. Exposure of the Cu(II) complex to humid air promoted the gradual replacement of the coordinated acetonitrile by water molecules, but the complex structure integrity remained. The EPR spectra exhibited signals attributed to the presence of a mixture of the monomeric (S = ½) and dimeric (S = 1) copper species in a possible 3:1 ratio. The magnetic studies revealed a peak at 50-100 K, which could be associated with the oxygen absorption capacity of the Cu(II)-vba complex.

Ion-Imprinted Polymer Structurally Preorganized Using a Phenanthroline-Divinylbenzoate Complex with the Cu(II) Ion as Template and Some Adsorption Results.

The novel [Cuphen(VBA)2H2O] complex (phen: phenanthroline, VBA: vinylbenzoate) was prepared and used as a functional monomer to preorganize a new ion-imprinted polymer (IIP). By leaching the Cu(II) from the molecular imprinted polymer (MIP), [Cuphen(VBA)2H2O-co-EGDMA]n (EGDMA: ethylene glycol dimethacrylate), the IIP was obtained. A non-ion-imprinted polymer (NIIP) was also prepared. The crystal structure of the complex and some physicochemical, spectrophotometric techniques were also used for the MIP, IIP, and NIIP characterization. The results showed that the materials are nonsoluble in water and polar solvents, which are the main features of polymers. The surface area of the IIP is higher than the NIIP demonstrated by the blue methylene method. The SEM images show monoliths and particles smoothly packed together on spherical and prismatic-spherical surfaces in the morphology of MIP and IIP, respectively. Moreover, the MIP and IIP could be considered as mesoporous and microporous materials, shown by the size of the pores determined by the BET and BJH methods. Furthermore, the adsorption performance of the IIP was studied using copper(II) as a contaminant heavy metal. The maximum adsorption capacity of IIP was 287.45 mg/g at 1600 mg/L Cu2+ ions with 0.1 g of IIP at room temperature. The Freundlich model was found to best describe the equilibrium isotherm of the adsorption process. The competitive results indicate that the stability of the Cu-IIP complex is higher than the Ni-IIP complex with a selectivity coefficient of 1.61.

Equilibrium Studies of Iron (III) Complexes with Either Pyrazine, Quinoxaline, or Phenazine and Their Catecholase Activity in Methanol.

Currently, catalysts with oxidative activity are required to create valuable chemical, agrochemical, and pharmaceutical products. The catechol oxidase activity is a model reaction that can reveal new oxidative catalysts. The use of complexes as catalysts using iron (III) and structurally simple ligands such as pyrazine (pz), quinoxaline (qx), and phenazine (fz) has not been fully explored. To characterize the composition of the solution and identify the abundant species which were used to catalyze the catechol oxidation, the distribution diagrams of these species were obtained by an equilibrium study using a modified Job method in the HypSpec software. This allows to obtain also the UV-vis spectra calculated and the formation constants for the mononuclear and binuclear complexes with Fe3+ including: [Fe(pz)]3+, [Fe2(pz)]6+, [Fe(qx)]3+, [Fe2(qx)]6+, [Fe(fz)]3+, and [Fe2(fz)]6+. The formation constants obtained were log ß110 = 3.2 ± 0.1, log ß210 = 6.9 ± 0.1, log ß110 = 4.4 ± 0.1, log ß210 = 8.3 ± 0.1, log ß110 = 6.4 ± 0.2, and log ß210 = 9.9 ± 0.2, respectively. The determination of the catechol oxidase activity for these complexes did not follow a traditional Michaelis-Menten behavior.

Stability of Manganese(II)-Pyrazine, -Quinoxaline or -Phenazine Complexes and Their Potential as Carbonate Sequestration Agents.

Carbonate sequestration technology is a complement of CO2 sequestration technology, which might assure its long-term viability. In this work, in order to explore the interactions between Mn2+ ion with several ligands and carbonate ion, we reported a spectrophotometric equilibrium study of complexes of Mn2+ with pyrazine, quinoxaline or phenazine and its carbonate species at 298 K. For the complexes of manganese(II)-pyrazine, manganese(II)-quinoxaline and manganese(II)-phenazine, the formation constants obtained were log ß110 = 4.6 ± 0.1, log ß110 = 5.9 ± 0.1 and log ß110 = 6.0 ± 0.1, respectively. The formation constants for the carbonated species manganese(II)-carbonate, manganese(II)-pyrazine-carbonate, manganese(II)-quinoxaline-carbonate and manganese(II)-phenazine-carbonate complexes were log ß110 = 5.1 ± 0.1, log ß110 = 9.8 ± 0.1, log ß110 = 11.7 ± 0.1 and log ß110 = 12.7 ± 0.1, respectively. Finally, the individual calculated electronic spectra and its distribution diagram of these species are also reported. The use of N-donor ligand with π-electron-attracting activity in a manganese(II) complex might increase its interaction with carbonate ions.

Synthesis, characterization, and biological activity studies of copper(II) mixed compound with histamine and nalidixic acid.

A mixed copper complex with deprotonated nalidixic acid (nal) and histamine (hsm) was synthesized and characterized by FTIR, UV-Vis, elemental analysis, and conductivity. The crystal structure of [Cu(hsm)(nal)H(2)O]Cl.3H(2)O (chn) showed a pentacoordinated cooper(II) in a square pyramidal geometry surrounded by two N atoms from hsm, two O atoms from the quinolone, and one apical water oxygen. Alteration of bacterial DNA structure and/or associated functions in vivo by [Cu(hsm)(nal)H(2)O]Cl.3H(2)O was demonstrated by the induction of a recA-lacZ fusion integrated at the amyE locus of a recombinant Bacillus subtilis strain. Results from circular dichroism and denaturation of calf thymus DNA (CT-DNA) suggested that increased amounts of copper complex were able to stabilize the double helix of DNA in vitro mainly by formation of hydrogen bonds between chn and the sugars of DNA minor groove. In vivo and in vitro biological activities of the chn complex were compared with the chemical nuclease [Cu(phen)(nal)H(2)O]NO(3) . 3H(2)O (cpn) where phen is phenanthroline.

Varying acidity of aqua ligands in dependence on the microenvironment in mononucleobase (nb) complexes of type cis- and trans-[Pt(NH3)2(nb)(H2O)]n+.

Aqua ligands in mixed aqua/nucleobase metal complexes are potential sites of acid-base catalysis and/or, when present as hydroxo ligands, can directly be involved in hydrolysis reactions. pKa values of close to 7 are consequently of particular interest and potential significance. Here we report on the differential acidity of aqua complexes in model nucleobase (nb) complexes of cis- and trans-[Pt(NH3)2 (nb)(H2O)]n+ and discuss reasons as to why the nb in cis complexes influences the pKa (pKa 4.8-7.0), whereas in trans complexes the pKa values are rather constant (pKa approximately 5.2-5.3). The results of DFT calculations of a series of mono(nucleobase) complexes derived from cis-Pt(NH3)2 are critically examined with regard to the role of exocyclic groups of nucleobases in stabilizing aqua/hydroxo ligands through intracomplex hydrogen bond formation. This applies in particular to the exocyclic amino groups of nucleobases, for which gas-phase calculations suggest that they may act as H bond acceptors in certain cases, yet in the condensed phase this appears not to be the case.