The coordination and extractive chemistry of the later 3d transition metal ions with N, N'-donor imidazole-based ligands
- Authors: Moleko, Pulleng
- Date: 2014
- Subjects: Solvent extraction , Coordination compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/8382 , vital:26352
- Description: The application of bidentate N,N'-donor ligands, such as 2,2'-biimidazole (BIIMH2) and 2,2'-pyridylimidazole (PIMH) and (1H-benzimidazol-2yl)-N-methylmethanamine (BIMAH), in the solvent extraction of base metal ions from an acidic sulfate/sulfonate medium was investigated. PIMH and BIMAH showed selectivity for Ni(II) with the only interfering ion being Cu(II) in the pH range 1.2-1.8 but BIIMH2 lacked selectivity. The extraction patterns observed were influenced by stereochemical aspects, and this agreed well with the envisaged design of nickel(II)-specific extractants through stereochemical “tailor-making” which is proposed in this study. The extraction patterns were explained from a coordination chemistry point of view using spectroscopic analysis and single crystal X-ray analysis to diagnose the geometry of the complexes formed from the interaction of the base metal ions with the ligands. The formation of the trigonal bipyrimidal [Cu(PIM)2(H2O)](SO4) complex, with a water molecule coordinated, while nickel(II) forms a square planar bisPIMH was put forward as the reason for extraction pattern observed with this ligand. Cobalt(II) also forms a bisPIMH complex but has two water molecules coordinated in the formation of a distorted octahedral complex, and this results in less extractable species. A similar observation as for PIMH was noticed in BIMAH complexation reactions. The BIIMH2 complexes were found to be distorted octahedral, through the bis-coordination of BIIMH2 and two sulfonate ions, resulting in lack of pH-metric separation of the later 3d metal ions. The stability constants data was in agreement with what was observed in the solvent extraction and coordination chemistry studies for the three ligand systems.
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- Date Issued: 2014
Advances in platinum-amine chemotherapeutic agents : their chemistry and applicationc
- Authors: Jaganath, Yatish
- Date: 2009
- Subjects: Coordination compounds , Antineoplastic antibiotics , Cancer -- Chemotherapy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10446 , http://hdl.handle.net/10948/d1021222
- Description: The research conducted in this study focussed on advancing the knowledge database of diamineplatinum complexes on two frontiers: 1) the development of novel anticancer complexes, and 2) improvements in their synthetic chemistry. Novel square-planar dichloro and oxalato platinum(II) complexes were synthesized as potential anticancer agents in accordance with a comprehensive set of factors identified as being significant in optimizing such action. The nonleaving ligands consisted of asymmetric chelating chiral diamines of the form 1- (1-R-imidazol-2yl)(R')methanamine (R representing methyl, butyl and R' methyl, phenyl). The complexes were characterized by a host of spectral, thermal and crystallographic techniques. In addition, the stabilities of the complexes were monitored in aqueous and saline solutions. Cytotoxicity screening on three cultured cancer cell lines (MCF-7, HeLa and HT29) indicated the compounds, present as their respective racemates, to have rather modest activities relative to cisplatin; with complexes having the smallest substituents, R,R' = methyl, being most active. In recognition of the limitations of traditional silver-based syntheses of oxalatoplatinum(II) complexes, innovative non-silver methods were developed using the well known cancer drug, oxaliplatin, (trans-R,R-1,2- diaminocyclohexane)oxalatoplatinum(II), as a prototype. These involved direct ligand exchange reactions of the dichloro precursor, (trans-R,R-1,2- diaminocyclohexane)dichloroplatinum(II), with tetrabutylammonium oxalate in essentially non-aqueous solvents. A 90:10 mixture of isoamyl alcohol (3-methyl- 1-butanol):water, proved to be a promising solvent, enabling the recovery of pure oxaliplatin (~98 percent) after 9 hours at 88 °C in yields of up to 86 percent. In light of the perceived unique mode of anticancer action available to mononitroplatinum(IV) complexes (i.e. their STAT3-binding potential), octahedral diamineoxalatoplatinum(IV) complexes containing axially-coordinated nitro and halo co-ligands were synthesized and extensively characterized. Electrochemical studies revealed trends in reduction potential which could be correlated to structural / chemical traits of the coordinated diamine and axial ligands. The similarities of the determined cytotoxicities of the platinum(IV) compounds and their respective platinum(II) analogues, implicated reduction as a means of activation of the platinum(IV) complexes.
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- Date Issued: 2009
Solvent-free synthesis of bisferrocenylimines and their coordination to rhodium (I)
- Authors: Kleyi, Phumelele Eldridge
- Date: 2009
- Subjects: Organic compounds -- Synthesis , Organic solvents , Solution (Chemistry) , Chemistry, Organic , Coordination compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10393 , http://hdl.handle.net/10948/1053 , Organic compounds -- Synthesis , Organic solvents , Solution (Chemistry) , Chemistry, Organic , Coordination compounds
- Description: Solvent-free reactions possess advantages compared to the solvent route, such as shorter reaction times, less use of energy, better yields, etc. Herein, the synthesis and characterization of bisferrocenylimines and arylbisamines are described. Reduction of the above compounds with LAH resulted in the formation of bisferrocenylamines and arylbisamines, respectively. The coordination chemistry of all the above compounds to rhodium(I) is also discussed in the prepared complexes [Rh(COD)(NN)]ClO4, where NN = bisferrocenylimines, and [Rh(COD)(NN)]BF4, where NN = bisferrocenylamines and arylbisamines. X-ray crystal structures of the complexes [Rh(COD)(NN)]ClO4 ([3.2] and [3.3]) have been obtained. Complexes of the type [Rh(COD)(NN)]BF4 were characterized with IR and UV-vis spectroscopy, cyclic voltammetry and conductometry. The catalytic activity of the complexes was also investigated: [Rh(COD)(NN)]ClO4 for the polymerization of phenylacetylene and [Rh(COD)(NN)]BF4 for the hydroformylation of styrene.
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- Date Issued: 2009
Novel aspects of platinum-amine coordination compounds: their chemistry and anticancer application
- Authors: Bouwer, Yolanda
- Date: 2008
- Subjects: Coordination compounds , Platinum compounds , Antineoplastic agents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10444 , http://hdl.handle.net/10948/d1021052
- Description: The aim in this thesis, was to synthesize novel platinum coordination compounds, in order to develop compounds with improved anticancer action which could lead to an improved understanding of the mechanism by which they operate and at the same time, improve synthetic methods for their products. The initial work included the development of a novel synthetic method for 1R,2R-diaminocyclohexaneoxalato-platinum(II) (oxaliplatin), by using an essentially non-aqueous solvent medium and direct ligand exchange at elevated temperatures. This was done by a study of the kinetics of the reaction in a variety of conditions; such as relative reagent concentrations and ratios as well as solvent mixtures. An effective method was developed which could be applied industrially. An international patent was taken out on this method. Various amine complexes of platinum(II) were synthesized using chloro, bromo and oxalato groups as leaving groups. The non-leaving groups were selected having certain specific characteristics in mind. Novel mononitroplatinum(IV) complexes were synthesized, mostly with oxalato leaving groups. One of these in particular, had excellent anticancer behaviour. Another trichloromononitro complex was also synthesized with very good anticancer properties. Two international patents were filed for the latter two compounds. As far as possible, all compounds were studied by spectrometric, chromatographic and thermal methods. They were also tested against 3 cancer cell lines namely cervical (Hela), Colon (HT29) and Breast (MCF7) cancer cells.
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- Date Issued: 2008
Exploratory studies of novel ligand systems
- Authors: Taylor, Steven John
- Date: 1992
- Subjects: Ligands , Coordination compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4315 , http://hdl.handle.net/10962/d1004973 , Ligands , Coordination compounds
- Description: A range of novel ligand systems have been developed in three distinct phases and preliminary studies have been initiated to evaluate their complexation potential. Phase I incorporated the synthesis of single strand ligand systems, which were mainly based on amino acid residues. Techniques have been developed for the attachment of these ligand systems onto, firstly, a styrene monomer, and then later onto a pseudo-styrene linking group, viz. the p-toluoyl group. The linking reactions were based on the formation of amides or esters by the reaction of an acid chloride system with an amine or alcohol. Phase II involved the synthesis of bis-chain ligand systems and their attachment onto the p-toluoyl linking group. A further linking group was also developed at this stage, viz. the xylyl group. In the preparation of phase II ligand systems, use was made of malonic ester and iminodiacetic acid derivatives. Phase III has involved the synthesis of cyclic ligand systems, with skeletons based upon the structures used in phase I and phase II and two crown ether type systems have been prepared.
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- Date Issued: 1992