My research interests are in the areas of synthetic inorganic chemistry and chemistry of materials. My main interest is to design and develop ligands that have the potential of forming metal complexes that exhibit interesting structural, magnetic, optical and electrochemical properties. Ligands are to be engineered in such a way as to endow them with characteristics that predispose them to forming complexes of desired properties.

Some of the on-going research activities are as follows:

1. Study of coordination properties of beta-hydroxyethenedithiocarboxylates and Derivatives. Currently, we are mainly engaged in the study of coordination and other properties of the ligands FcC(-OH)=CHCSS- , which is abbreviated FSS-, and Fcbis[C(-OH)=CHCSS- ], a bbreviated FBSS-, where Fc is the ferrocenyl group. Note that when protonated, FSS- becomes FSSH and FBSS- becomes FBSSH.

In the case of FSSH, one starts with the reaction of acetylferrocene, FcCOCH3, with carbon disulfide, CS2, in the presence of potassium t-butoxide to form the product, whose formula and structure are given below. Both FSS- and FBSS- can function as either S,S or O,S donors towards metal species, depending on how hard or soft the metal ion is. Ligating properties of these ligands towards hard and soft Lewis acids, are currently being investigated by us.



Part of the objective of this project is to transform FSSH and FBSSH into various optically active ligands. Schematic structures of some of the possible ligands are given below.



The syntheses and characterization of the chirogenic camphoryl dithiocarboxylic acid (CACSSH) and its derivative (CAKSSAC), whose schematic structures are shown below, are in progress.



The ultimate objective is to synthesize the ligands and then study their chiroptical and other properties when complexed to various metal ions as well as in the presence of various chiral cationic metal complexes such as [M(en)3]3+, for M=Co, Cr, Ni. Also the project is directed at investigating the ability of the ligands and their metal complexes to discriminate, through chemical or physical modes of interaction, chemical substances based on chirality. Furthermore, an effort is being made to use these ligands or their complexes as catalysts for asymmetric synthesis. 2. Another research area is concerned with the synthesis and study of complexes between metal species and ligands derived from curcuminoid molecules. Curcumin and related molecules bear phenolic groups that are capable of undergoing condensation reactions with formaldehyde to give polymers or oligomers similar to phenol-formaldehyde polymers. Taking advantage of the fact that curcumoids, through their beta-diketonate moities, form fairly stable complexes with metal ions, the objective of this project is to use various metal ions as templates for the reaction of curcuminoid ligands with formaldehyde with the hope of making metal-ion imprinted curcuminoid-formaldehyde materials. Such materials may higher affinity and selectivity for metal ions used as a template for a particular batch. Applications of metal ion-imprinted polymers, MIIPs, include solid phase extraction, metal ion sensors and membranes design and development of sensors for inorganics for formulating appropriate pollution control. Highly selective transport of one particular metal ion in the presence of other coexisting inorganics via MIIP membranes may find application for treating large volumes of industrial effluents.



Characterization of Reaction Products Using Single Crystal X-ray Crystallography and Other Techniques

In order to identify and characterize reaction products, a combination of a number of techniques is used. They include ORD, CD, nuclear magnetic resonance, mass, infrared and UV-visible spectroscopic methods as well as elemental analysis.

Experimental data obtained from the techniques listed above may yield important information concerning the composition and structure of chemical materials. However, such information is always incomplete, fragmentary and ambiguous. In fact there are many compounds of industrial and academic importance for which an unambiguous structure cannot be deduced based on data from all the above techniques combined. It turns out that single crystal x-ray crystallography is uniquely capable of unambiguously revealing complete three-dimensional structures including bond distances, bond angles, hydrogen bonding and, if the chemical substance has chirality, the absolute stereochemical configuration. So far, x-ray diffraction, especially single crystal, is the most powerful method known for obtaining atomic arrangement in the solid state. In light of the above, efforts are being invested in growing crystals suitable for x-ray crystallography.

Powder x-ray diffraction can also be used to determine crystal structures. However, the information content is significantly reduced in comparison with single crystal x-ray diffraction and data problems can make solving a crystal structure difficult.

Recent Publications:

1. J. K. Kiptoo, J. C. Ngila, N D. Silavwe, Solid-Phase Extraction of Zn(II), Cu(II), Ni(II) and Pb(II) on Poly(vinyl chloride) Modified with 3-Ferrocenyl-3-hydroxydithioacrylic acid and Their Subsequent Determination by Electrothermal Atomic Absorption Spectrometry, Microchimica Acta, Ref.: Manuscript. No. MCA-D-07-00059R1 (2007), Accepted for publication

2. J. Catherine Ngila, Ned D. Silavwe, Jackson K. Kiptoo and Jonathan E.R. Thabano.Voltammetric investigation of the distribution of hydroxo-, chloro-, EDTA and carbohydrate complexes of Pb, Cr, Zn, Cd & Cu: potential application to metal speciation studies in brewery wastewater, Bullettin of the Chemical Society Ethiopia 19(1) (2005) 111-124.

3. J. Ahmad and N. D. Silavwe “Behaviour of 1-Octadecanethiol Film Spread Over Silver Nitrate Solution” Asian Journal of Chemistry 2002, 14(3), 1282-86.