Research articles (Dept of Chemistry)

Search within this collection:

Browse by

By Issue Date
Authors
Titles
Subjects

Recent Submissions

A study of the removal of heavy metals from aqueous solutions by Moringa oleifera seeds and amine-based ligand 1,4-bis[N,N-bis(2-picoyl)amino]butane

Obuseng, V.; Nareetsile, F.; Kwaambwa, H.M. (Elsevier Science Ltd, www.elsevier.com/locate/aca, NaN, 2012)

[more]

[less]

Abstract:

Uptake for lead, copper, cadmium, nickel and manganese from aqueous solution using the Moringa oleifera seeds biomass (MOSB) and amine-based ligand (ABL) was investigated. Experiments on two synthetic multi-solute systems revealed that MOSB performed well in the biosorption and followed the decreasing orders Pb(II)>Cu(II)>Cd(II)>Ni(II)>Mn(II) and Zn(II)>Cu(II)>Ni(II). The general trend of the heavy metal ions uptake by the amine-based ligand followed decreased in the order Mn>Cd >Cu> Ni>Pb, which is the reverse trend for what was observed for MOSB. Comparing the single- and multi-metal solutions, there was no clear effect in the biosorption capacity of MOSB suggesting the presence of sufficient active binding sites for all metal ions studied. The MOSB performance is also not affected by pH in the range 3.5–8.

URI:

http://hdl.handle.net/10311/1039

Files in this item: 1

Obuseng_ACA_2012.pdf (886.0Kb)

Intermediate and ion-pair formation in the outer-sphere reactions between azido-pentacyanocobaltate(III) and iron(II) polypyridyl complexes in aqueous medium

Ogunlusi, G.O.; Ige, J.; Oyetunji, O.A.; Ojo, J.F. (Springer Science+Business Media B.V., http://www.springer.com/chemistry/journal/11243, NaN, 2009)

[more]

[less]

Abstract:	The kinetics of the reactions between azidopentacyanocobaltate(III), Co(CN)5N3 3-, and iron(II) polypyridyl complexes, Fe(LL)3 2? (LL = bipy, phen), have been studied in both neutral and acidic aqueous solutions at I = 0.1 mol dm-3 NaCl. The reactions were carried out under pseudo-first-order conditions in which the concentration of Fe(LL)32+ was kept constant, and the second-order rate constants obtained for the reactions at 35 C were within the range of 0.156–0.219 dm3 mol-1 s-1 for LL = bipy and 0.090–0.118 dm3 mol-1 s-1 for LL = phen. Activation parameters were measured for these systems. The dependence of reaction rates on acid was studied in the range [H+] = 0.001–0.008 mol dm-3. The reaction in acid medium shows interesting kinetics. Two reactive species were identified in acid medium, namely, the protonated cobalt complex and the azido-bridged binuclear complex. The electron-transfer process is proposed to go by mixed outerand inner-sphere mechanisms in acid medium, in which electron transfer through the bridged inner-sphere complex (k5) is slower than through the outer-sphere path (k4).
Description:	Symbols may not appear as they are in the original abstracts.
URI:	http://hdl.handle.net/10311/1035

Files in this item: 1

Ogunlusi_TMC_2009.pdf (948.9Kb)

Cyclic voltammetric studies of tris(alkylisocyanide)-bis(triarylphosphine)cobalt(II) and tris-(alkylisocyanide)bis(triarylphosphine)cobalt(I) complexes exhibiting synthetic interconvertability

Ahmad, J.; Bothata-Nareetsile, F.; Becker, C.A.L. (NRC Research Press, http://www.nrcresearchpress.com/loi/cjc, NaN, 2003)

[more]

[less]

Abstract:	Nine pairs of corresponding [CoI(CNR)3(PR3 ′ )2]X, [CoII(CNR)3(PR3 ′ )2]X2 complexes — where X = ClO4, BF4; CNR = CNCMe3, CNCHMe2, CNC6H11, CNCH2Ph; PR3′ = PPh3, P(C6H4Me-p)3, P(C6H4OMe-p)3 — have been studied using cyclic voltammetry in CH3CN solutions. All cycles are reversible, and E1/2 for the Co(I) complexes, initially oxidized, are within experimental error identical to E1/2 values for the corresponding Co(II) complexes, initially reduced. E1/2 values are strongly dependent on the triarylphosphine ligand, decreasing in the order PPh3 > > P(C6H4Me-p)3 > P(C6H4OMe-p)3, and weakly dependent on the alkylisocyanide ligand, decreasing in the order CNCH2Ph > CNCMe3 > CNC6H11 ≥ CNCHMe2. Solution ν(-N C) IR patterns reveal that the [CoI(CNR)3(PR3′)2]X complexes do not have regular trigonal bipyramidal coordination, their structure being determined by the particular CNR ligand, while the [CoII(CNR)3(PR3′)2]X2 complexes, specifically in CF3CH2OH, appear to have regular trigonal bipyramidal coordination.
Description:	Signs on the abstract may be different to the original document
URI:	http://hdl.handle.net/10311/1034

Files in this item: 1

Ahmad_CJC_2003.pdf (782.1Kb)

Kinetic studies on the reactions of some tetrakis(arylisocyanide)cobalt(II) complexes with pyridine in 2,2,2-trifluoroethanol

Oyetunji, O.A.; Paphane, B.D.; Becker, C.A.L. (Springer, http://www.springer.com/chemistry/journal/11243, NaN, 2006)

[more]

[less]

Abstract:

The interaction of pyridine with four tetraki(arylisocyanide)cobalt(II) complexes, [Co(CNR)4(ClO4)2] R = 2,6- Me2C6H3 (A), 2,4,6-Me3C6H2 (B), 2,6-Et2C6H3 (C) and 2,6-iPr2C6H3 (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 , increase from A to D while the activation entropies, DS , 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.

URI:

http://hdl.handle.net/10311/1033

Files in this item: 1

Oyetunji_TMC_2006.pdf (911.4Kb)

Bis(pyrazolyl) palladium(II), platinum(II) and gold(III) complexes: Syntheses, molecular structures and substitution reactions with L-cysteine

Keter, F.K.; Ojwach, S.O.; Oyetunji, O.A.; Guzei, I.A.; Darkwa, J. (Elsevier Science Ltd, www.elsevier.com/locate/ica, NaN, 2009)

[more]

[less]

Abstract:

A series of pyrazolyl palladium(II), platinum(II) and gold(III) complexes, [PdCl2(3,5-R2bpza)] {R = H (1), R = Me (2), bpza = bis-pyrazolyl acetic acid}, [PtCl2(3,5-R2bpza)] {R = H (3a), R = Me (4)}, [AuCl2(3,5- R2bpza)]Cl {R = H (5a), R = Me (6a)} and [PdCl2(3,5-R2bpzate)] {R = Me (7)} have been synthesised and structurally characterised. Single crystal X-ray crystallography showed that the pyrazolyl ligands exhibit N^N-coordination with the metals. Anticancer activities of six complexes 1–6a were investigated against CHO cells and were found to have low activities. Substitution reactions of selected complexes 1, 2, 3a and 5a with L-cysteine show that the low anticancer activities compounds and that the rate of substitution with sulfur-containing compounds is not the cause of the low anticancer activities.

URI:

http://hdl.handle.net/10311/1032

Files in this item: 1

Keter_ICA_2009.pdf (1.240Mb)

Research articles (Dept of Chemistry)

Research articles (Dept of Chemistry)

Browse by

Recent Submissions

Search DSpace

Browse

All of DSpace

This Collection

My Account