Samson O. Owalude

Synthesis of copper–isonicotinate metal–organic frameworks simply by mixing solid reactants and investigation of their adsorptive properties for the removal of the fluorescein dye

The formation of [Cu(INA)2] (INA = isonicotinate) metal–organic frameworks (MOFs) by a highly efficient and environmentally benign method simply by mixing and heating solid reactants without milling has been investigated. The materials were characterized using elemental analysis, FT-IR spectroscopy and powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). Comparison of PXRD patterns of the materials with patterns simulated from single crystal X-ray diffraction data allowed identification of the products. The adsorption properties of [Cu(INA)2] were studied using the fluorescein dye (FS). The adsorption data followed both Langmuir and Freundlich equations but was best suited to the Langmuir model. The adsorption data were also correlated with the Temkin and Dubinin–Radushkevich adsorption model and the results showed that the adsorption process is physical. These results indicate that the adsorption of FS on [Cu(INA)2] is partly due to electrostatic interaction between fluorescein and the adsorbent. Compared with the traditional synthetic techniques, this method for the synthesis of MOFs was found to be highly efficient, environmentally benign and useful for the large-scale production.

Synthesis of zinc-carboxylate metal-organic frameworks for the removal of emerging drug contaminant (amodiaquine) from aqueous solution

We herein report the removal of amodiaquine, an emerging drug contaminant from aqueous solution using [Zn2(fum)2(bpy)] and [Zn4O(bdc)3] (fum=fumaric acid; bpy=4,4-bipyridine; bdc=benzene-1,4-dicarboxylate) metal-organic frameworks (MOFs) as adsorbents. The adsorbents were characterized by elemental analysis, Fourier transform infrared (FT-IR) spectroscopy, and powder X-ray diffraction (PXRD). Adsorption process for both adsorbents were found to follow the pseudo-first-order kinetics, and the adsorption equilibrium data fitted best into the Freundlich isotherm with the R2 values of 0.973 and 0.993 obtained for [Zn2(fum)2(bpy)] and [Zn4O(bdc)3] respectively. The maximum adsorption capacities foramodiaquine in this study were found to be 0.478 and 47.62mg/g on the [Zn2(fum)2(bpy)] and [Zn4O(bdc)3] MOFs respectively, and were obtained at pH of 4.3 for both adsorbents. FT-IR spectroscopy analysis of the MOFs after the adsorption process showed the presence of the drug. The results of the study showed that the prepared MOFs could be used for the removal of amodiaquine from wastewater.

KINETICS OF OXIDATION OF D-ARABINOSE AND D-XYLOSE BY VANADIUM (V) IN THE PRESENCE OF MANGANESE II AS HOMOGENEOUS CATALYST

Kinetics of oxidation of D-arabinose and D-Xylose by acidic solution of Vanadium (V) ions in the presence of manganese (II) has been reported. First-order dependence of the reaction rate was observed on [sugars] and [H+] at low concentrations throughout the oxidation reaction and a zeroth-order dependence on [sugar] and [H+] was observed at high concentrations. First-order kinetics with respect to [Mn (II)] was also observed throughout the oxidation for both sugars. The effect of Cl- concentration was found to be negligible. The reaction rates increases with the ionic strength of the medium. Various activation parameters were evaluated and provide further support to the proposed mechanism. Formic acid was reported as one of the oxidation products of the sugars

Bis(acetonitrile-κN)dichlorido(η4-cyclo­octa-1,5-diene)ruthenium(II) acetonitrile monosolvate

In the title RuII complex, [RuCl2(C8H12)(C2H3N)2]·CH3CN, the metal ion is coordinated to the centers of each of the double bonds of the cyclooctadiene ligand, to two chloride ions (in cis positions) and to two N-atom donors (from MeCN molecules) that complete the coordination sphere for the neutral complex. The coordination about the RuII atom can thus be considered to be octahedral with a slightly trigonal distortion. There is also one acetonitrile solvent molecule per molecule which is outside the coordination sphere of the ruthenium atom.

Spectral studies of transition metal complexes of dihydrobis(1-pyrazoyl)borate with some Lewis bases

Abstract Co(II), Ni(II) and Cu(II) complexes of dihydrobis(1-pyrazolyl)borate and their adducts with some Lewis bases have been prepared and characterized by elemental analyses, IR and UV–vis spectroscopic techniques. The adducts were either 1:1 or 1:2 complexes depending on whether the Lewis base was bidentate or monodentate. The results indicate that adducts with 1,10-phenanthroline were the most stable due to the chelating effect of the Lewis base. The order of reactivity of the complexes was determined to be Ni(H2BPz2)2 > Cu(H2BPz2)2 > CoH2(BPz2)2 > Co(H2BPz2)2. The effects of various solvents (i.e., benzene, chloroform and DMF) on the structure were studied. The solvents appear to minimally affect the visible spectra of Co(H2BPz2)2. The Ni(H2BPz2)2 and Cu(H2BPz2)2 adducts exhibit a four-coordinate structure in non-coordinating solvents. However, in coordinating solvents, such as DMF, the adducts exhibit six-coordinate structures.

Facile synthesis and vapochromic studies of Co(II) complexes bearing NO and OO donor ligands

Abstract Two Co(II) complexes containing malonic and isonicotinic acids have been prepared by manual grinding of stoichiometric amounts of the starting materials. Elemental analysis (CHN), IR, UV-vis spectroscopic techniques, TGA-DTG investigation and X-ray powder diffraction analysis were used to characterize the two compounds. Isonicotinic acid coordinated to the metal via the pyridine ring nitrogen and one oxygen atom of the carboxylic group while malonic acid coordinated via both oxygen atoms of the carboxylate groups indicating bidentate coordination mode in the two compounds. The compounds were exposed to some volatile organic compounds (VOCs) containing nitrogen or oxygen donor atoms in the solid state and their vapochromic behaviours studied using colour changes, FT-IR and solid state UV-vis spectroscopies. Heating the samples exposed to the VOCs for a few minutes at 100 °C regenerates the original material without degradation, even after several heating cycles.

Synthesis, crystal structure and desulfurization properties of zig-zag 1D coordination polymer of copper(II) containing 4-methoxybenzoic acid ligand

ABSTRACT Combustion of fuels containing organosulfur compounds has resulted in the emission of sulfur oxides (SOx) into the atmosphere, therefore, causing serious environmental and health hazards. Herein, slightly distorted octahedral zig-zag 1D coordination polymer of copper(II) [Cu(4-mba)2(H2O)3] was synthesized by reacting copper sulfate pentahydrate with a carboxylate-containing ligand (H-4mba = 4-methoxybenzoic acid) and employed for sulfur compound uptake. The ligand coordinates to the copper(II) atom via two pairs of deprotonated ligating atoms (carboxylate oxygens) and two water molecules. Structural characterization also reveals that interplay of O–H···O, N–H···O, C-H···O and C–H···π interactions between lattice and coordinated water and ligands significantly contribute to the crystal packing leading to the formation and strengthening of three-dimensional supramolecular assembly. The complex, [Cu(4-mba)2(H2O)3], show potential for desulfurization of fuel with an observed adsorption capacity of 9.6 mg/g at 32°C for 6 h. DFT calculations further revealed a transfer of electron sulfur-containing compounds and the complex, [Cu(4-mba)2(H2O)3], thus leading to a stronger pi–pi interaction. GRAPHICAL ABSTRACT

Synthesis of new ruthenium(II) complexes derived from labile nitrile ligands: an alternative route to the preparation of trans-dichlorotetrakis(diphenylphosphine)ruthenium(II)

Abstract New ruthenium(II) complexes containing labile nitrile ligands have been prepared by treatment of either the polymer [{RuCl2(COD)}x] (COD = cycloocta-1,5-diene) (1) or its derivative [RuCl2(COD)(NCCH3)2]·NCCH3 (2) with the appropriate nitrile ligands in refluxing acetonitrile under argon. A new route to synthesis of trans-dichlorotetrakis(diphenylphosphine)ruthenium(II) (7) was also reported. A redetermination of the structure of 7 was undertaken and X-ray crystallographic data revealed that the complex crystallizes in the triclinic space group P-1 with unit cell dimensions a = 12.7016(9) Å, b = 13.0847(10) Å, c = 14.1498(10) Å, α = 101.46(3)°, V = 2080.6(3) Å3, Z = 2 and R = 0.0309. Its polymorph 7′ was also obtained. The crystal structure of 4 was also determined. This complex crystallizes in the monoclinic space group C2/c with unit cell dimensions a = 27.0510(3) Å, b = 11.0984(13) Å, c = 13.0450(16) Å, α = 90°, V = 3886.5(8) Å3, Z = 8 and R = 0.0282.

Synthesis, thermal properties, and biological study of metal(II) nicotinamide complexes containing fumarate dianion and fumaric acid: Crystal structure of [Ni(H2O)4(nia)2](fum)·(H2fum)

ABSTRACT New divalent transition metal nicotinamide (nia) complexes containing fumarate (fum) dianion and fumaric acid (H2fum), [M(H2O)4(nia)2](fum)·(H2fum) [M = Co (1), Cu (2), and Ni (3)] have been synthesized.The compounds were characterized by elemental analyses, infrared, UV-vis, XRPD, and TGA. Structural analysis of 3 using single-crystal X-ray diffraction technique revealed that the Ni(II) ion is coordinated by four aqua and two nia ligands in an octahedral geometry. The structure of 3 is completed with fumarate (fum2−) dianion acting as a counterion while fumaric acid (H2fum) is present as a molecule of solvation. The three complexes were investigated for biological activities.