Mononuclear, homo- and hetero-binuclear complexes of 1-(5-(1-(2-aminophenylimino)ethyl)-2,4-dihydroxyphenyl)ethanone: synthesis, magnetic, spectral, antimicrobial, antioxidant, and antitumor studies

<p>A new Schiff base, H₂L, was prepared by condensation of 4,6-diacetylresorcinol with <i>o</i>-phenylenediamine in molar ratio 1 : 1. The ligand reacted with copper(II), nickel(II), cobalt(II), iron(III), zinc(II), oxovanadium(IV), and dioxouranium(VI) ions in the absence and presence of LiOH to yield mononuclear and homobinuclear complexes. The mononuclear dioxouranium(VI) complex [(HL)-(UO₂)(OAc)(H₂O)]·5H₂O was used to synthesize heterobinuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, ¹H-, and ¹³C-NMR, electronic, ESR and mass spectra, conductivity, and magnetic susceptibility measurements as well as thermal analysis. In the absence of LiOH, mononuclear complexes (<b>1</b>, <b>4</b>, and <b>9</b>) were obtained; in the presence of LiOH, binuclear complexes (<b>3</b>, <b>5</b>, <b>7</b>, and <b>10</b>) as well as mononuclear complexes (<b>2</b>, <b>6</b>, and <b>8</b>) were obtained. In the mononuclear complexes, the coordinating sites are the phenolic oxygen, azomethine nitrogen, and amino nitrogen. In addition to these coordinating sites, the free carbonyl and phenolic OH are involved in coordination in binuclear complexes. The metal complexes exhibited octahedral, tetrahedral, and square planar geometries while the uranium is seven-coordinate. The antimicrobial and antioxidant activities of the ligand and its complexes were investigated. The ligand and the metal complexes showed antitumor activity against Ehrlich Acites Carcinoma.</p

Synthesis and characterization of N₃S₂ donors macrocyclic copper(II) complexes. Catechol oxidase and phenoxazinone synthase biomimetic catalytic activity

<p>A new series of copper(II) complexes have been synthesized with macrocyclic ligands L¹ and L² having N₃S₂-donating atoms in the 12-membered macrocyclic ring. The structure characterization of these newly synthesized copper(II) complexes was achieved by various physicochemical techniques. It has been shown that the stereochemistry of complexes is dependent on the type of counter anions incorporated in the complex molecule. Mimicking copper oxidase enzymes, namely catechol oxidase and phenoxazinone synthase, was investigated and the results obtained demonstrated that there is a correlation between the structural properties of these copper(II) complexes and the oxidase biomimetic catalytic activities. Kinetic measurements revealed second-order dependence on the catalyst concentration for 3,5-DTBCH₂ and first order in the case of OAPH. On the other hand, for the substrate concentration dependence, a saturation-type behavior was detected for both 3,5-DTBCH₂ and OAPH. Addition of Lewis base, triethylamine, in both systems exhibits dramatic effect on the rate of these catalytic aerobic oxidation reactions. The probable mechanistic implications of both catalytic systems are discussed.</p