Justin Nenwa

Nickel (II) and Iron (II) Complexes with Azole Derivatives: Synthesis, Crystal Structures and Antifungal Activities

Two new complexes of nickel (II) with 4-amino-3, 5-bis(pyridyl)-1, 2, 4-triazole (abpt) and iron (II) with 2-(3-phenyl-1H-pyrazole-5-yl) pyridine (phpzpy) have been synthesized and characterized by elemental analysis and IR spectroscopy. The crystal structures of the complexes have been determined by single crystal X-ray diffraction techniques. In the nickel and iron complexes, the ligands are coordinated through nitrogen atoms in bidentate manner. The ligands and their respective complexes have been tested for their antifungal activity against Aspergillus niger, Aspergillus flavus, and Candida albicans. From the study, the complexes showed enhanced activities against the tested organisms compared to the ligands.

A Dimeric Copper(II) Complex of Oxalate and Oxamide Dioxime Ligands: Synthesis, Crystal Structure, Thermal Stability, and Magnetic Properties

The dimeric copper(II) complex [Cu(C2O4)(H2oxado)(H2O)]2 (1), where H2oxado=oxamide dioxime, has been synthesized in water and characterized by elemental and thermal analyses, IR spectroscopy, and single-crystal X-ray diffraction. Complex 1 is composed of two neutral [Cu(C2O4)(H2oxado)(H2O)] entities connected by Cu-O bonds between oxalate oxygen atoms and copper(II) ions, thereby producing a centrosymmetric dimer, with the Cu(II) centers exhibiting a strongly distorted octahedral coordination. Neighboring dimers are hydrogen-bonded through O- H···O interactions leading overall to a layer structure. Thermal analyses of complex 1 showed two significant weight losses corresponding to the coordinated water molecules, followed by the decomposition of the network. Variable-temperature (10 - 300 K) magnetic susceptibility measurements revealed very weak antiferromagnetic interactions (θ = 0:86 K from Curie-Weiss law behavior) within the dinuclear unit Graphical Abstract A Dimeric Copper(II) Complex of Oxalate and Oxamide Dioxime Ligands: Synthesis, Crystal Structure, Thermal Stability, and Magnetic Properties

Crystal structure of quinolinium trans-diaquabis(oxalato-0,0')- chromate(III), [C9H8N][Cr(H2O)2(C2O4)2]

Discussion The oxalate ion has recently moved into the focus of a considerable research activity around the world, due to its unique potential as a remarkably flexible ligand system in complexations with a wide range of metal ions [1]. In the past decades, many coordination compounds based on this ligand system were shown to play a crucial role in the rational design and development of novel materials that may combine, within a given system, a range of interesting solid state functionalities [2], such as molecular magnetism, optical activity, nano-channels in metal-organic frameworks (MOFs) [3], extended hydrogen-bonding. Such polyfunctional materials are needed to boost the advancement of the new millennium technologies. The unit cell of the title salt contains four formula units, each of which consists of a quinolinium cation and a [Cr(H20)2(C204>2]~ anion (figure, top). These discrete ions are stacked into segregated positive and negative layers parallel to (001), whereby the planar positive and the corrugated negative layers alternate along the [001] direction, being interconnected via N-H—O bridgings (¿(Nl-Ol) = 2.887(4) Â) that link the quinolinium N-H groups to the coordinated oxalato O atoms (dashed lines, figure, bottom). The quinolinium stacks are centered on a 2-fold axis which extends throughout the lattice across the centers of the superimposed benzenic ring systems, in eclipsed configuration and 3.77 À apart, revealing weak π-π interactions within these stacks. The cations and the main planes of the complex anions of this salt are disposed in a fish-bone fashion, defining the respective dihedral angles of 63.50° and 56.91° with respect to (001). The bond lengths and angles within the quinolinium cation are in accord with reported values [4]. The complex anions contain Cr(m) centers in a prolate (4+2) octahedral coordination of two chelating, equatorial oxalato ligands and two axial water molecules, the equatorial Cr—O bond lengths ranging from 1.955(1) to 1.976( 1) Â, and the axial Cr—O distances being virtually identical at 2.000(2) and 2.002(2) À. The shortest intralayer Cr-Cr spacing is d(Cr-Cr) = 6.635(1) Â. Abstract Ci3Hi2CrNOio, monoclinic, P12i/cl (no. 14), a = 7.541(1) À, b = 10.936(2) Â, c = 18.594(3) λ,β = 94.261(3)°, V = 1529.2 Â, Ζ = 4, Rgt(F) = 0.035, wR^F*) = 0.115, Γ =294 Κ.

Two tris(oxalato)ferrate(III) hybrid salts with pyridinium derivative isomers as counter cations: synthesis, crystal structures, thermal analyses, and magnetic properties

Abstract Two organic–inorganic hybrid salts, tris(2-amino-4,6-dimethylpyridinium) tris(oxalato)ferrate(III), (C7H11N2)3[Fe(C2O4)3] (1), and tris(4-dimethylaminopyridinium) tris(oxalato)ferrate(III) tetrahydrate, (C7H11N2)3[Fe(C2O4)3]·4H2O (2), have been synthesized and characterized by elemental and thermal analyses, IR spectroscopy, single-crystal X-ray diffraction, and SQUID magnetometry. Compounds 1 and 2 crystallize in triclinic P-1 and monoclinic C2/c space groups, respectively. Each compound contains the anionic complex [Fe(C2O4)3]3- in which the central metal is six-coordinate in a slightly distorted octahedron defined by three chelating oxalate(2-) ligands. The two substituted pyridinium cations are isomers. However, due to the great steric hindrance provided by the bulky cation, 2-amino-4,6-dimethylpyridinium, only the 4-dimethylaminopyridinium cation, the smallest of this series, led to formation of 2 with enough vacant spaces to be occupied by four solvent water molecules. In the crystals, cations and anions are connected via hydrogen-bonds of the types N–H⋯O in 1 and N–H⋯O and O–H⋯O in 2, with π–π stacking interactions between the pyridine rings stabilizing the 3-D framework. The thermal studies confirmed the anhydrous character of salt 1 and the presence of water molecules in salt 2. The magnetic susceptibility measurements in the 2–300 K temperature range revealed weak antiferromagnetic coupling in the two salts.

Anionic Nanochanneled Silver-Deficient Oxalatochromate(III) Complex with Hydroxonium as Counter Ion: Synthesis, Characterization and Crystal Structure

Reaction of Ba0.50[Ag2Cr(C2O4)3]·5H2O with Ag2SO4 in an aqueous solution of sulfuric acid (pH ≈ 3) yielded the silver(I)/chromium(III) oxalate salt H0.50[Ag2.50Cr(C2O4)3]·5H2O (1). Compound 1 can be best described as an anionic silver-deficient oxalatochromate(III) complex [Ag2.50Cr(C2O4)3]0.5- with nanochannels containing hydrogen-bonded water molecules and protons. Thermal analyses show significant weight losses corresponding to the elimination of water molecules of crystallization followed by the decomposition of the network.

Crystal structure of 4-(di­methyl­amino)­pyridinium cis-di­aqua­bis­(oxalato-κ2O,O′)ferrate(III) hemihydrate

In the title compound, the FeIII atom is bonded to four O atoms from two chelating oxalate dianions and two O atoms from two cis aqua ligands. It has a slightly distorted octahedral coordination geometry. In the crystal, N—H⋯O and O—H⋯O hydrogen bonds play an important role in the structural self-assembly.

Crystal structure of tris­[4-(di­methyl­amino)­pyridinium] tris­(oxalato-κ2O,O′)chromate(III) tetra­hydrate

In the crystal structure of the title compound, the molecular components, viz. 4-(dimethylamino)pyridinium cations, tris[oxalatochromate(III)] anions and lattice water molecules, are linked through O—H⋯O and N—H⋯O hydrogen bonds into a three-dimensional network. Additional π–π interactions between pyridinium rings stabilize this arrangement.

{[Na1(-H2O)Na2]2[(C2O4)2Cr(-OH)2Cr(C2O4)2]·H2O}n, a novel hydrated form

The unit cell of the title compound, poly[[μ-aqua-μ-hydroxido-di-μ-oxalato-chromium(III)disodium] monohydrate], {[CrNa2(C2O4)2(OH)(H2O)]·H2O}n, contains four [Na1(μ-H2O)Na2][(C2O4)2Cr(μ-OH)·H2O] formula units, each of which consists of two crystallographically independent Na+ sites (bridged by one aqua ligand), one half of a centrosymmetric di-μ-hydroxido-bis[cis-bis(oxalato)chromate(III)] dimer, [(C2O4)2Cr(μ-OH)2Cr(C2O4)2]4−, and one uncoordinated water molecule. The structure is best described as a coordination polymer in which the three-dimensional lattice framework is realized by the interconnection of the metallic atoms via the O atoms of the aqua, hydroxide and oxalate ligands. One Na atom is heptacoordinated by one water, one hydroxide and five oxalate O atoms, whilst the other is pentacoordinated by one water and four oxalate O atoms. The coordination around the Cr3+ sites is pseudo-octahedral, involving four aqua and two hydroxide O atoms. Adjacent Na atoms are separated by 3.593 (2) Å, whereas the intradimer Cr⋯Cr spacing is 2.978 (1) Å. The crystal structure is consolidated by extended relatively weak O—H⋯O hydrogen bonding with O⋯O distances ranging from 2.808 (4) to 3.276 (5) Å.

Crystal structure of catena-bis[aqua-μ-(2S,3S)-tartratocobalt(II)] trihydrate, [Co(H2O)(C4H4O6)]2 · 3H2O, a new polymorph

C8H18Co2O17, orthorhombic, P21212 (no. 18), a = 11.141(2) Å, b = 7.864(1) Å, c = 9.053(2) Å, V = 793.1 Å, Z = 2, Rgt(F) = 0.035, wRref(F) = 0.083, T = 173 K. Source of material 2 mmol (500 mg) of Co(CH3COO)2 · 4H2O crystals were dissolved in 60 ml of 333 K warm water. With stirring, 2 mmol (300 mg) of pure L(+)-tartaric acid were added in successive portions whereby a pink-red precipitate formed. After stirring over 1.5 h, the reaction mixture was cooled to room temperature, the solid filtered off, washed with 3 portions of 5 ml of water and dried in air. The mother liquor was concentrated to near complete dryness, the resulting solid was treated likewise and the combined crops yielded 400 mg (> 97 %) of material. Recrystallization from water at room temperature over several weeks produced good crystals used for X-ray diffraction. Experimental details The water H atoms were positioned geometrically as riding on their parent atoms and refined with distance restraints of d(O—H) = 0.85(3) Å and d(H···H) = 1.39(3) Å. All other H atoms were located in a difference Fourier map and then refined without distance restraints.