Olayinka Oyetunji - Academia.edu (original) (raw)

Papers by Olayinka Oyetunji

Molecular Simulation, Nov 22, 2023

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Advances in Biological Chemistry, 2012

Metal(II) coordination compounds of glycine and phenylalanine were synthesized and characterized ... more Metal(II) coordination compounds of glycine and phenylalanine were synthesized and characterized using infrared and electronic spectroscopic, and magnetic susceptibility measurements. The complexes were tested for antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Methicillin Resistant Staphylococcus aureus (MRSA), Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris and Candida albicans. The stoichiometric reaction between the metal (II) ions and ligands in molar ratio M:L (1:3) [where M = Mn, Co, Ni, Cu and Cd; L= glycine; phenylalanine] resulted in the formation of five-coordinate square pyramidal dinuclear geometry for both copper complexes and six-coordinate octahedral geometry for the other complexes. The spectroscopic and magnetic moment data suggested that the ligands coordinated via both their amino and carboxylate ion moieties. The complexes demonstrated better activities against one or more of the tested microbes than acriflavine, the standard drug used.

ACS omega, Mar 15, 2022

Biodiesel is one of the emerging renewable sources of energy to replace fossil-fuel-based resourc... more Biodiesel is one of the emerging renewable sources of energy to replace fossil-fuel-based resources. It is produced by a transesterification reaction in which a triglyceride reacts with methanol in the presence of a catalyst. The reaction is slow because of the low solubility of methanol in triglycerides, which results in low concentrations of methanol available to react with triglyceride. To speed up the reaction, cosolvents are added to create a single phase which helps to improve the concentration of methanol in the triglyceride phase. In this study, molecular dynamics simulations are used to help understand the role of cosolvents in the solvation of triglyceride (triolein). Six binary mixtures of triolein/cosolvent were used to study the solvation of triolein at 298.15 K. Results of 100 ns simulations at constant temperature and pressure to simulate mixing experiments show that in the first 10 ns all the binary mixtures remain largely unmixed. However, for the cosolvents that are fully miscible with triolein, the partial densities across the simulation boxes show that the systems are fully mixed in the final 10 ns. Some solvents were found to interact strongly with the polar part of triolein, while others interacted with the aliphatic part. The radial distribution functions and clustering of the solvents around triolein were also used as indicators for solvation. The presence of cosolvents also influenced the conformation of triolein molecules. In the presence of solvents that solubilize it, triolein preferred a propeller conformation but took up a trident conformation when there is less or no solubilization. The results show that tetrahydrofuran is the best solvent at solubilizing triolein, followed by cyclopentyl methyl ether, diethyl ether, and hexane. With 1,4-dioxane, the solubility improves with an increase in temperature. The miscibility of a solvent in triolein is aided by its ability to interact with both the polar and nonpolar parts of triolein.

Transition Metal Chemistry, Oct 1, 2006

The interaction of pyridine with four tetrakis(arylisocyanide)cobalt(II) complexes, [Co(CNR) 4 (C... more The interaction of pyridine with four tetrakis(arylisocyanide)cobalt(II) complexes, [Co(CNR) 4 (ClO 4) 2 ] R = 2,6-Me 2 C 6 H 3 (A), 2,4,6-Me 3 C 6 H 2 (B), 2,6-Et 2 C 6 H 3 (C) and 2,6-iPr 2 C 6 H 3 (D), have been studied in 2,2,2-trifluoroethanol medium. The kinetics of the reactions were investigated over the 293-318 K temperature range. The reaction profile exhibited two distinct processes, proposed to be an initial fast substitution followed by a slow reduction, for each of the reactions. The pseudo first-order rate constants for both processes increased with increasing concentration of pyridine with the reduction processes exhibiting saturation kinetics at high pyridine concentrations. Steric hindrance plays a significant role in the rates of the reactions, as the rates decrease in the order k(A) > k(B) > k(C) > k(D). The activation enthalpies, DH à , increase from A to D while the activation entropies, DS à , are relatively similar for the four reactions, indicating similar transition states and hence similar mechanisms. Complex B was first synthesized and characterized in this study.

Transition Metal Chemistry, Apr 1, 1996

The reduction of chloro-, bromo-and iodopentacyanocobaltate(III) anions by aquatitanium(III) has ... more The reduction of chloro-, bromo-and iodopentacyanocobaltate(III) anions by aquatitanium(III) has been studied in aqueous solution with ionic strength, I = 1.0moldm-3 (LiC1, KBr or KI) at T= 25 ~ The dependence of the observed second-order rate constant, /Cobs, on IN +] has been investigated over the acid range 0.005-0.100 mol dm 3 and is of the general limiting form: kobs ~ ko + k[H +] 1, where k o is appreciable in all cases and k is a composite rate constant. Using values of K a (associated with the Ti m hydrolytic equilibrium constant), obtained from the kinetic data for the TiI"/Co nl redox reactions, and comparison of the rate constants obtained with those for the corresponding V II reductions of the same Co In complexes, it is concluded that the Ti m reductions of these halopentacyanocobaltate(III) complexes proceed via an outer-sphere mechanism.

Journal of Coordination Chemistry, Jun 25, 2013

ABSTRACT The reactions of freshly prepared solutions of [Co(CNC8H17-t)5](ClO4)2 with three triary... more ABSTRACT The reactions of freshly prepared solutions of [Co(CNC8H17-t)5](ClO4)2 with three triarylphosphines, PR3 (R = Ph, C6H4Me-p, C6H4OMe-p), were investigated in dichloromethane under pseudo-first-order conditions and with temperatures maintained at ± 0.1 °C. Addition of each of the phosphines to the Co(II) complex solutions results in a shift in the λ max of the electronic spectra accompanied by a change in color of the solution. The shift is attributed to ligand substitution. Analyses of the kinetic data suggest a general rate law given by: Rate = . Overall, the reactions of the cobalt(II) complex [Co(CNC8H17-0t)5]2+ with the triarylphosphines are proposed to proceed via substitution/reduction mechanisms with final formation of disubstituted Co(I) complexes. The order of reactivity of the complex with the triarylphosphines was P(C6H4OMe-p)3 > P(C6H4Me-p)3 > PPh3. This order is explained in terms of the electron donating/π-acceptor properties of the phosphines.

Bulletin of the Chemical Society of Japan, Feb 1, 1990

Journal of The Chemical Society-dalton Transactions, 1987

Substitution Reactions between Penta-ammineaquaruthenium(ii) and Thiocyanato, Protonated Acetato,... more Substitution Reactions between Penta-ammineaquaruthenium(ii) and Thiocyanato, Protonated Acetato, Cyano, and Oxalato Ligands in Aqueous Acidic Solutions ... J. Folorunso Ojo, Olusegun OlUbUyide," and Olayinka Oyetunji Department of Chemistry, University of lfe, fle-ffe, ...

DOAJ (DOAJ: Directory of Open Access Journals), 1994

Bull. Chem. Soc. Ethiop. 1994, 8(2), 61-67

South African journal of chemistry, 2021

We have prepared several pyrazolyl palladium and nickel complexes ([(L1)PdCl 2 ] (1), [(L2) PdCl ... more We have prepared several pyrazolyl palladium and nickel complexes ([(L1)PdCl 2 ] (1), [(L2) PdCl 2 ] (2), [(L3) PdCl 2 ] (3), [(L1) NiBr 2 ] (4), [(L2) NiBr 2 ] (5) and [(L3) NiBr 2 ] (6)) by reacting 3,5-dimethyl-1H-pyrazole (L1), 3,5-di-tert-butyl-1H-pyrazole (L2) and 5-ferrocenyl-1H-pyrazole(L3) with [PdCl 2 (NCMe) 2 ] or [NiBr 2 (DME)] to afford mononuclear palladium and nickel complexes, respectively. These complexes were then investigated as pre-catalysts in the hydrogenation of 2,4-hexadienoic acid (sorbic acid). The active catalysts from these complexes demonstrate significant activities under mild experimental conditions. Additionally, the active catalysts show that the hydrogenation of sorbic acid proceeds in a sequential manner, where the less hindered C=C bond (4-hexenoic acid) is preferentially reduced over the more hindered C=C bond (2-hexenoic acid).

InTech eBooks, Dec 6, 2017

The reactions of four tetrakis(arylisocyanide)cobalt(II) complexes, [Co(CNR) 4 (ClO 4) 2 ] {R = 2... more The reactions of four tetrakis(arylisocyanide)cobalt(II) complexes, [Co(CNR) 4 (ClO 4) 2 ] {R = 2,6-Me 2 C 6 H 3 (A), 2,4,6-Me 3 C 6 H 2 (B), 2,6-Et 2 C 6 H 3 (C), and 2,6-iPr 2 C 6 H 3 (D)}, with two pyridines, 4-CNpy and 4-Mepy, have been kinetically studied in trifluoroethanol medium. Each of the reactions, which was monitored over a temperature range of 293 to 318 K, exhibited two distinct processes proposed to be an initial fast substitution process followed by a slow reduction process. For each pyridine, steric hindrance was observed to play a significant role in the rates of the reactions, which decrease with increasing size of the arylisocyanide ligand in the order k(A)>k (B)>k (C)>k (D). Addition of each of three triarylphosphines, PR 3 (R = Ph, C 6 H 4 Me-p, C 6 H 4 OMe-p), to solutions of pentakis (t-octylisocyanide)cobalt(II), [Co(CNC 8 H 17-t) 5 ](ClO 4) 2 , resulted in a shift in the λ max of the electronic spectrum accompanied by a change in color of the solutions. The shift is attributed to ligand substitution. The reactions of the cobalt(II) complex [Co(CNC 8 H 17-t) 5 ] 2+ with the triarylphosphines are proposed to proceed via a combination of substitution, reduction, and disproportionation mechanisms with final formation of disubstituted Co (I) complexes. The order of reactivity of the complex with the triarylphosphines was found to be P(C 6 H 4 OMe-p) 3 >P (C 6 H 4 Me-p) 3 >P P h 3. This order is explained in terms of the electron donating/π-acceptor properties of the phosphines.

Inorganica Chimica Acta, Sep 1, 1986

The hydroxo ligand (OH) has been shown to be a more effective bridging ligand than the aqua ligan... more The hydroxo ligand (OH) has been shown to be a more effective bridging ligand than the aqua ligand (H,O), to the extent that the rate ratios kon:kn,o have been used [l-4] to diagnose the mechanisms of some electron-transfer reactions. When substitutionlabile reductants such as U3+, Cr3+, Eu*+, Cu+, V*+ [l-4] reduce hydroxo and aqua complexes, very high rate ratios koH:kr.r,o are obtained and innersphere mechanism is proposed; but when substitution-inert reductants such as Ru(NH~)~*+ [S] and Cr(bipy),*+ [2] are employed, low rate ratios are obtained and outer-sphere mechanism is proposed. Here we report the reductions of Co(NH3)sXn+ (X = H20, OH, n = 2 or 3) and the pentacyanoanalogues Co(CN)sX"-by the mild and moderately substitution-labile reductant Ru(NH3)sH202+. This reductant is much less substitution-labile than U3+, Cr*+ Eu*+ etc., but more substitution-labile than Ru(NH3)e2+ [6]. The inclusion of the pentacyano analogues of the oxidants (Co(CN)sXT is aimed at investigating the effect which the replacement of the five u-bonded ammonia ligands in Co(NH3)s-Xn' by five n-bonded cyano ligands (Co(CN)sX") could have on the redox reactivity of cobalt(II1) ion centre. Moreover, these two types of cobalt(II1) complexes are oppositely charged and their interactions with Ru(NH3)sH202+ could lead to different redox behaviours. Experimental Materials CO(NH~)~H~O~+ was synthesised and characterised as described in literature [7]. Co(CN)sH202-was prepared in situ from COINER-[8,9] as described in literature and it was kept in vessels wrapped with aluminium foil because of its light-sensitivity [9]. It was certified pure by its IR and UV-Vis absorption spectra [lo]. Co(NH,),O~' and *Author to whom correspondence should be addressed. Co(CN)sOH3-were generated in situ from the aqua analogues at alkaline pH using NH3/NH4C1 buffer

Asian Journal of Chemistry

Hexadentate ligand of the type N,N,N′,N′-tetrakis(2-pyridylmethyl)alkanediamine (where alkane is ... more Hexadentate ligand of the type N,N,N′,N′-tetrakis(2-pyridylmethyl)alkanediamine (where alkane is butane (L1), hexane (L2) and octane (L3) reacted with Ni(ClO4)2·6H2O (stoichiometry 1:1) in alcoholic solutions yielding mononuclear complexes of the type [Ni(L)](ClO4)2·xH2O. The ligand L1 reacted with Ni(ClO4)2·6H2O in ethanol medium to give a violet powder of [Ni(L1)](ClO4)2·3H2O. The other mononuclear nickel(II) complexes using L2 and L3 were synthesized in methanol solution to give violet powders of [Ni(L2)](ClO4)2·2H2O and [Ni(L3)](ClO4)2·2H2O, respectively. All the three complexes were characterized by IR and elemental analysis. The X-ray crystallographic results for the purple crystals of [Ni(L1)](ClO4)2·3H2O shows the octahedral geometry on the Ni(II) ions together with the tetrahedral perchlorate anions separated from the [Ni(L1)]2+ cation. The crystal structure data show monoclinic space group P 21/c; a = 17.1748(10), b = 9.8273(6), c = 17.8146(10) Å; α = 90º, β = 95.0200(10)º...

Inorganics, 2021

Metal-organic frameworks have attracted a great deal of attention for future applications in nume... more Metal-organic frameworks have attracted a great deal of attention for future applications in numerous areas, including gas adsorption. However, in order for them to reach their full potential a substrate to provide an anchor may be needed. Ideally, this substrate should be environmentally friendly and renewable. Cellulose nanofibrils show potential in this area. Here we present a hybrid material created from the self-assembly of zeolitic imidazolate framework (ZIF-8) nanocrystals on cellulose nanofibrils (CNF) in aqueous medium. The CNF/ZIF-8 was freeze dried and formed free standing materials suitable for gas adsorption. A BET area of 1014 m2 g−1 was achieved for the CNF/ZIF-8 hybrid materials ZIF-8@cellulose which is comparable with reported values for free standing ZIF-8 materials, 1600 m2 g−1, considering the dilution with cellulose, and a considerable enhancement compared to CNF on its own, 32 m2 g−1.