Ghezai T. Musie

Synthesis, crystal structure and redox properties of bis-imidazolyl-containing copper(II) complexes

Abstract Two copper(II) complexes, [Cu(L1)Cl]Cl and [Cu(L2)Cl]Cl, with tetradentate ligands L1=N,N′-bis[(1-methylimidazol-2-yl)methyl]-1,3-diaminopropan-2-ol and L2=N,N′-bis[(1-methylimidazol-2-yl)methyl]-1,3-diaminopropane were prepared and characterized. Ligands L1 and L2 were synthesized by NaBH4 hydrogenation of the corresponding Schiff bases obtained from condensation of 1-methyl-2-imidazolecarboxaldehyde with 1,3-diaminopropan-2-ol and 1,3-diaminopropane, respectively. The crystal structures of the complexes are determined by X-ray diffraction. The complexes display a square-pyramidal geometry about the copper centers coordinating with Cl− and N4 donor set of the ligands. Electrochemical studies indicate that the complexes undergo quasi-reversible one-electron reduction in both acetonitrile and aqueous solutions.

Synthesis and characterization of new mono- and heptazinc complexes with unusual amide coordination modes

Two novel, a mono- and a heptanuclear, zinc complexes have been prepared and characterized by exploiting the flexibility and chelating and bridging ability of a new carboxylate- and amide-rich dinucleating ligand under different reaction conditions.

Synthesis, Characterization, and Spectroscopic Investigation of New Iron(III) and Copper(II) Complexes of a Carboxylate Rich Ligand and Their Interaction with Carbohydrates in Aqueous Solution

New tetra-iron(III) (K4[1]·25H2O·(CH3)2CO and K3[2]·3H2O·(OH)) and di-copper(II) (Na3[3]·5H2O) complexes as carbohydrate binding models have been synthesized and fully characterized used several techniques including single crystal X-ray crystallography. Whereas K4[1]·25H2O·(CH3)2CO and Na3[3]·5H2O are completely water-soluble, K3[2]·3H2O·(OH) is less soluble in all common solvents including water. The binding of substrates, such as d-mannose, d-glucose, d-xylose, and xylitol with the water-soluble complexes in different reaction conditions were investigated. In aqueous alkaline media, complexes K4[1]·25H2O·(CH3)2CO and Na3[3]·5H2O showed coordination ability toward the applied substrates. Even in the presence of stoichiometric excess of the substrates, the complexes form only 1:1 (complex/substrate) molar ratio species in solution. Apparent binding constants, pKapp, values between the complexes and the substrates were determined and specific mode of substrate binding is proposed. The pKapp values showed that d-mannose coordinates strongest to K4[1]·25H2O·(CH3)2CO and Na3[3]·5H2O. Syntheses, characterizations and detailed substrate binding study using spectroscopic techniques and single crystal X-ray diffraction are reported.

Hexacoordinated cobalt(II) and nickel(II) complexes of a novel mixed ligand, N-(2-methylpyridine)-2-aminomethyl benzoic acid: structures, spectroscopic characterizations and redox studies

Abstract Two new metal complexes, [Co(Mamba) 2 ] and [Ni(Mamba) 2 ], have been prepared by the treatment of the tridentate ligand N -(2-methylpyridine)-2-aminomethyl benzoic acid (HMamba) with the respective metal salts (Co(ClO 4 ) 2 and Ni(C 2 H 3 O 2 ) 2 ) in the presence of sodium hydroxide. The ligand was synthesized by reduction of the Schiff base which was obtained by condensation of 2-carboxybenzaldehyde with 2-(aminomethyl)pyridine. The complexes have been characterized using single crystal X-ray diffraction and other spectroscopic techniques. The structures of the complexes are octahedral with each metal center chelated to two ligands through the amine nitrogen atom, the pyridine nitrogen atom and benzoic acid oxygen atom of each Mamba − . In solid state, an extended networks of H-bonding between cocrystallized solvent molecules and the metal complexes have been observed. Electrochemical studies of the complexes revealed the presence of metal-based one electron quasi-reversible reduction in acetonitrile.

Synthesis, crystal structure and investigation of mononuclear copper(II) and zinc(II) complexes of a new carboxylate rich tripodal ligand and their interaction with carbohydrates in alkaline aqueous solution.

A new carboxylate rich asymmetric tripodal ligand, N-[2-carboxybenzomethyl]-N-[carboxymethyl]-β-alanine (H3camb), and its di-copper(II), (NH4)2[1]2, and di-zinc(II), ((CH3)4N)2[2]2, complexes have been synthesized as carbohydrate binding models in aqueous solutions. The ligand and complexes have been fully characterized using several techniques, including single crystal X-ray diffraction. The interactions of (NH4)2[1]2 and ((CH3)4N)2[2]2 with D-glucose, D-mannose, D-xylose and xylitol in aqueous alkaline media were investigated using UV-Vis and (13)C-NMR spectroscopic techniques, respectively. The molar conductance, NMR and ESI-MS studies indicate that the complexes dissociate in solution to produce the respective complex anions, 1(-) and 2(-). Complexes 1(-) and 2(-) showed chelating ability towards the naturally abundant and biologically relevant sugars, D-glucose, D-mannose, D-xylose, and xylitol. The complex ions bind to one molar equivalent of the sugars, even in the presence of stoichiometric excess of the substrates, in solution. Experimentally obtained spectroscopic data and computational results suggest that the substrates bind to the metal center in a bidentate fashion. Apparent binding constant values, pK(app), between the complexes and the substrates were determined and a specific mode of substrate binding is proposed. The pK(app) and relativistic density functional theory (DFT) calculated Gibbs free energy values indicate that D-mannose displayed the strongest interaction with the complexes. Syntheses, characterizations, detailed substrate binding studies using spectroscopic techniques, single crystal X-ray diffraction and geometry optimizations of the complex-substrates with DFT calculations are also reported.

Inorganic Phosphate and Arsenate within New Tetranuclear Copper and Zinc Complexes: Syntheses, Crystal Structures, Magnetic, Electrochemical, and Thermal Studies

Three, PO43–/HPO42– and AsO43–-incorporated, new tetranuclear complexes of copper(II) and zinc(II) ions have been synthesized and fully characterized. In methanol–water, reactions of H3cpdp (H3cpdp = N,N′-Bis[2-carboxybenzomethyl]-N,N′-Bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol) with copper(II) chloride in the presence of either NaOH/Na2HPO4·2H2O or KOH/Na2HAsO4·7H2O lead to the isolation of the tetranuclear complexes Na3[Cu4(cpdp)2(μ4-PO4)](OH)2·14H2O (1) and K2[Cu4(cpdp)2(μ4-AsO4)](OH)·162/3H2O (2), respectively. Similarly, the reaction of H3cpdp with zinc(II) chloride in the presence of NaOH/Na2HPO4·2H2O yields a tetranuclear complex, Na(H3O)2[Zn4(cpdp)2(μ4-HPO4)]Cl3·121/2H2O (3). All complexes are characterized by single-crystal X-ray diffraction and other analytical techniques, such as Fourier transform infrared and UV−vis spectroscopy, thermogravimetric and electrochemical studies. The solid-state molecular framework of each complex contains two monocationic [M2(cpdp)]+ (M = Cu, Zn) units, which are exclusively coordinated to either phosphate/hydrogen phosphate or arsenate groups in a unique mode. All three complexes exhibit a μ4:η1:η1:η1:η1 bridging mode of the PO43–/HPO42–/AsO43– groups, with each bridging among four metal ions. The thermal properties of all three complexes have been investigated by thermogravimetric analysis. Low-temperature magnetic studies of complexes 1 and 2 disclose moderate antiferromagnetic interactions mediated among the copper centers through alkoxide and phosphate/arsenate bridges. Electrochemical studies of complexes 1 and 2 in dimethylformamide using cyclic voltammetry reveal the presence of a fairly assessable one-electron metal-based irreversible reduction and one quasireversible oxidation couple.

Structure and properties of a novel staircase-like decanuclear [CuII10] cluster supported by carbonate and carboxylate bridges

This article describes a novel staircase-like decanuclear copper(II) cluster [CuII10(cpdp)4(CO3)4(CH3OH)2]·3.33CH3OH·7.83H2O (1) (H3cpdp = N,N′-bis[2-carboxybenzomethyl]-N,N′-bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol) composed of a pair of [CuII5] pentamers. In methanol, the reaction of H3cpdp with Cu(NO3)2·3H2O in the presence of K2CO3 leads to the isolation of complex 1. This complex has been characterized by various analytical techniques including single crystal X-ray crystallography. Structural analysis reveals that the two [CuII5] pentameric units are bridged together exclusively by two μ2:η2:η1 carbonate groups. Complex 1 shows a rare μ3:η2:η1:η1 bridging coordination mode of four benzoate groups of cpdp3− ligands with each bridging among three copper(II) ions. Complex 1 also represents the first example of a carbonate-coordinated decanuclear copper(II) cluster with any class of bridging or non-bridging ligand. Thermal, magnetic, EPR and electrochemical properties of this complex have been discussed. Variable temperature magnetic measurement discloses the antiferromagnetic interactions among the copper(II) ions. Electrochemical investigation of 1 in methanol solution using cyclic voltammetry reveals the presence of one metal-based quasi-reversible reduction at 870 mV (ΔEp = 190 mV).

Crystal structure of gluconate bound iron(III) complex: synthesis, characterization and redox properties of the complex in aqueous solution

A novel tetra-iron(III) complex, K6[Fe4(ccdp)2(μ-O)(μ-OH)(D-GluA)2](NO3)3·10H2O (K6[1](NO3)3·10H2O) with two gluconato and two N,N′-bis[2-carboxobenzomethyl]-N,N′-bis[carboxomethyl]-1,3-diaminopropan-2-oxy (ccdp5−) ligands has been synthesized and fully characterized using different techniques including single crystal X-ray crystallography. K6[1](NO3)3·10H2O showed stability aqueous solution, in biological samples such as human and fetal bovine serum (HS and FBS) and cell cultures such as phosphate buffer saline and minimum essential medium (PBS and MEM) using UV-Vis spectroscopy at room temperature and 37 °C. The redox behavior of the complex was studied using cyclic and square wave voltammetries in aqueous and DMF solutions. Furthermore, magnetic study using electron paramagnetic resonance spectroscopy and Guoy balance magnetic moment measurements indicated antiferromagnetic coupling among the metal centers of the (μ-O)(μ-OH) bridged tetra-iron(III) anion core of the complex. Electrochemical studies of the K6[1](NO3)3·10H2O in aqueous and DMF solutions using cyclic and square-wave voltammetries revealed the presence of multi-accessible electron metal-based redox events.

1,12-Bis(2-carboxy-phen-yl)-5,8-dioxa-2,11-diaza-dodecane-2,11-diium dichloride methanol solvate.

In the title salt hydrate, C22H30N2O6 2+·2Cl−·CH4O, the dication adopts a U-shaped conformation whereby the benzene rings are splayed out from the chain linking them. All components of the asymmetric unit are linked into a cohesive entity by a combination of O—H⋯Cl−, N+—H⋯Cl− and N+—H⋯O charge-assisted hydrogen-bonding interactions. The assemblies thus formed are linked into supramolecular helical chains along [010] via C—H⋯O contacts. The resulting chains are, in turn, consolidated into the three-dimensional crystal structure by C—H⋯π contacts.

Bis(tetra­methyl­ammonium) tetra­chlorido­zincate(II), phase VI

Phase VI of bis(tetramethylammonium) tetrachlorozincate(II), (C4H12N)2[ZnCl4], contains three formula units per asymmetric unit. Several short C—H⋯Cl contacts [2.70 (3) and 2.72 (4) Å] are observed, but they are believed to participate only in van der Waals interactions. The crystal studied exhibited inversion twinning.