X-ray crystallography, electrochemistry, spectral and thermal analysis of some tetradentate schiff base complexes and formation constant measurements

<p>A series of new transition metal Schiff base complexes was synthesized via the reaction of H₂L (N,N′-bis(naphthylidene)-2-aminobenzylamine) with the transition metals (Cu²⁺, Co²⁺, Ni²⁺, Zn²⁺ and Mn²⁺) and characterized by elemental analysis, ¹HNMR, FT-IR, UV-Vis spectroscopy, thermogravimetric analysis(TG) and in selected cases by X-ray crystallography. Thermodynamics of complex formation, electrochemistry of the metal Schiff base complexes and kinetic aspects of thermal decomposition of the complexes were also studied. The obtained formation constants change according to the following trend due to the electronegativity and Jahn-Teller effects of the central transition metals: Cu > Co > Ni > Zn >Mn. Cyclic voltammogram of the complexes in acetonitrile was done to evaluate the redox behavior of the complexes. Electrochemistry of these complexes showed a redox reaction without any successive reactions. Furthermore, kinetic parameters which calculated by Coats–Redfern equation revealed a first-order kinetics of thermal decomposition in all stages.</p

Cyanuric chloride reagent as a chloride ion donor: synthesis, crystal structure, and magnetic properties of [Cu₂(2-APM)₂(μ-Cl)₂(μ-OCH₃)₂]_<i>n</i> coordination polymer

<div><p>A new chloro- and methoxo-bridged Cu(II) coordination polymer, [Cu₂(2-APM)₂(μ-Cl)₂(μ-OCH₃)₂]_<i>n</i>·CH₃OH (<b>1</b>), was prepared using <i>in situ</i> formed chloride by the decomposition of cyanuric chloride and 2-aminopyrimidine (2-APM) as a ligand in methanol. Its solid-state structure has been characterized by elemental analysis and single crystal X-ray diffraction. X-ray crystallographic studies reveal that this compound has an extended 2-D supramolecular architecture directed by strong hydrogen bonds and aromatic <i>π</i>–<i>π</i> stacking interactions. Compound <b>1</b> shows an antiferromagnetic coupling exchange with coupling constants of −58.2 and −41.4 cm⁻¹ between adjacent copper(II) ions, in agreement with the intermetallic distances of 3.0405(5) and 3.6073(5) Å found in the crystal structure.</p></div

Synthesis, crystal structures, antimicrobial activities, and DFT calculations of two new azido nickel(II) complexes

<div><p>Two new complexes, [Ni(HL¹)(N₃)(μ_1,1N₃)]₂ (<b>1</b>) [HL¹: NC₅H₄CH₃C=NNH (C=O) NH₂] and [Ni(L²)N₃] (<b>2</b>) [HL²: NC₅H₄HC=N NH(C=S)NH₂], have been synthesized by reaction of Ni(OAC)₂·4H₂O and sodium azide with HL¹ and HL² and characterized by elemental analysis, FT-IR, and UV–vis spectral studies. Single-crystal X-ray diffraction reveals that <b>1</b> is dinuclear with nickel(II) in an octahedral environment of NNO donors of HL¹, two nitrogens of azide bridges and one nitrogen of terminal azide; <b>2</b> is mononuclear containing nickel(II) in a distorted square-planar environment of NNS donors of HL² and one terminal azide. The structures of <b>1</b> and <b>2</b> have been optimized by density functional theory. The results of antimicrobial activities of ligands, <b>1</b> and <b>2</b> demonstrated that HL² and <b>2</b> have good antimicrobial activity in contrast with HL¹ and <b>1</b>, related to the presence of sulfur donor in HL².</p></div