Ni(II) mixed-ligand complexes of [NiLNH3] (where L= N-salicylidene-o-aminophenol (L1), N-(5-methoxysalicylidene-o-aminophenol) (L2) and N-(2-hydroxy-1-naphthalidene)-o-aminophenol) (L3) containing ONO tridentate Schiff bases and ammonia were synthesized and characterized by elemental analysis, infrared, ultraviolet-visible, proton and carbon-13 spectroscopies. Theoretical calculations were also performed on the optimized structures of the Ni(II) mixed-ligand complexes. The Infrared and ultraviolet-visible spectra of the complexes were calculated, and the results compared with the corresponding experimental spectra to augment the experimental structural identification. The elemental analysis data confirmed the formation of 1:1:1 [metal: Schiff base: ammonia] molar ratio. The NMR spectra showed that the Schiff bases coordinated to the Ni(II) ion via the two deprotonated phenolic oxygen and azomethine nitrogen atoms. The biological studies showed that the complexes exhibited higher antibacterial and antioxidant activities than the free Schiff base ligands.
Properties of raw sawdust ofParkia biglobosa, as a biosorbent for the removal of Acid Blue 161 dye in single, binary, and ternary dye systems with Rhodamine B and Methylene Blue dyes in aqueous solution, were investigated. The sawdust was characterized using Scanning Electron Microscopy, Fourier Transform Infrared spectrophotometry, X-ray diffraction, and pH point of zero charge. Batch adsorption experiments were carried out to determine the equilibrium characteristics, thermodynamics, and kinetics of the sorption processes. The data obtained were subjected to various isotherm and kinetics equations. The results showed that the adsorption processes were described by different isotherm models depending on the composition of the system; they were all spontaneous (ΔGranges from −0.72 to −5.36 kJ/mol) and endothermic (range ofΔHis 11.37–26.31 kJ/mol) and with increased randomness withΔSvalues of 55.55 and 98.78 J·mol/K for single and ternary systems, respectively. Pseudo-second-order kinetics model gave better fit for all the sorption systems studied irrespective of the differences in composition, with the initial and overall rate constants higher for the mixtures than for the single system (6.76 g·mg−1min−1). The presence of Rhodamine B and Methylene Blue had a synergetic effect on the maximum monolayer capacity of the adsorbent for Acid Blue 161 dye.
African black soap is an indigenous African organic soap formed by esterification. This was prepared by reacting palm kernel oil and the filtrate of cocoa pod ash. Chemical analyses revealed the moisture content was 26% (w/w), total fatty matter (TFM) was 44.75% (w/w), total fatty alkaline (TFA) was 0.22% (w/w), total alkaline (TA) was 11.78% (w/w) and pH was 10. The metal complexes were formed by the reaction of the synthesized black soap with some transition metal salts which included Cu(CH 3 COO) 2 Characterization of the black soap and complexes was done by spectroscopic analyses and determination of physicochemical properties. The solubility of the metal complexes was determined at room temperature in various solvents. Results showed that solubility increased as polarity decreased and it was most effective with non-polar organic solvents. Potassium ester (C 11 H 23 COO -K + ), commonly called African black soap, has acted either as a monodentate or bidentate ligand forming metal complexes by coordinating through one or two of its oxygen donor atoms and also by entirely replacing the potassium ion with the transition metal (displacement reaction). Spectra analyses corroborate an octahedral structure for the Pb(II), a distorted octahedral structure for the Cu(II) and an octahedral Fe(III) complex.
The formation constants of binary and ternary complexes of Thiobarbituric acid as primary ligand and L-tyrosine and L-histidine as secondary ligands have been examined in 40% (v/v) ethanol-water mixture at 27oC and 35oC and at ionic strength of 0.02 NaNO3 by potentiometric method. The ligands formed 1:1 binary complexes with the metal ions. The primary and secondary ligands simultaneously coordinated to the metal ions to form 1:1:1 ternary complexes. The difference in stability constants of binary and ternary complexes were determined by DlogK and RS%. Ternary complexes exhibited enhanced stability than the binary complexes. The stability of the complexes decrease with increase in temperature. The thermodynamic parameters such as Gibb’s free energy change (ΔG), entropy change (ΔS) and enthalpy change (ΔH) accompany the interactions were evaluated. The interactions were found to be spontaneous, exothermic, and entropically favoured.
The electronic structures of model methyl and methoxyl substituted benzoic acid hydrazides of Ni(II) and Cu(II) complexes have been studied both at semi empirical level (PM3). Theortho-methoxyl is relatively stable which may be due to the formation of hydrogen bonds between methoxyl oxygen and hydrogen on hydrazide (CH30---HNNH; 1.817Å for Cu(II) and 1.806∼1.839∼ for Ni(II)). The change in torsion in the complexes affectπ-electrons delocalization (complexes containingπ-electrons system) and consequently affect the band gap which is a measure of electronic properties that control the reactivity of the complexes. The curves fororthoandparamethoxyl substituted Cu(II) complexes intercept at 50°and 135°-144°, this could suggest that both complex ions can co-exist and react in very similar ways in solution under certain conditions.
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