Staff-Academic Profile- MSW

MSW Research Group Group Leader – Dr. Marvadeen Singh-Wilmot

Current Students: Zeyar Min

Saddi Gilbert Shalik Walker (undergraduate)

Past Student: Rochette Sinclair.

Dr. Singh-Wilmot at the World Economic Forum, Tianjin China.

Dr. Marvadeen Singh-Wilmot is a lecturer in Inorganic Chemistry and Crystallographer at UWI, Mona. Her research group currently consists of two graduate students and an undergraduate researcher and aims to make new molecules from a group of metals called rare earths (or lanthanides). The rare earths are metals with exciting and unique light emitting and magnetic properties. They have applications in phosphors (substances which give off visible light when exposed to radiation, for example those substances that make your television glow with various colours), light-emitting diodes (responsible for the displays on various electronic devices and the light in traffic signals etc), sensors and MRI contrast

enhancement agents (enchances a MRI image) , to name a few. While Singh-Wilmot has published on a variety of new lanthanide containing molecules and still continues work on rare earth nanoclusters (multiple lanthanides in a cluster whose dimensions are in the nanometer range), most of her attention is currently focused on using lanthanides to assemble Metal Organic Framework Materials (MOFs). Singh-Wilmot has a passion for science and is committed to the promotion of science as a tool for development. She served as co-chair of the Young Scientist Ambassador Program (YSAP) which is an initiative of The Young Scientists from the 2010 Annual Meeting of the New Champions (AMNC), Summer Davos. This program involves Young Scientists from 55 different countries representing every section on the Globe and will promote the efforts of AMNC Young Scientists to bridge the international scientific gap by facilitating cultural, scientific, intellectual, or educational interactions. Singh-Wilmot is a mentor and a motivator. She has been recognized various times for her contribution to teaching at UWI as determined by excellent scores in teaching assessment done by students. She spends at least one hour per week working with children from various Primary and Prep Schools in St. Andrew, getting them excited about science and its opportunities. In October 2010 she was inducted as a Young Affiliate Fellow of the Academy of Sciences for the Developing World (TWAS) in Hyderabad India. She is the first Young Affiliate to be selected from the Caribbean Region.

Singh-Wilmot and her students have discussions with collaborator, Christopher Cahill from George Washington University.

(Clockwise direction - Saddi Gilbert (red shirt), Rochette Sinclair, Chris Cahill, Marvadeen Singh-Wilmot and Zeyar Min)

Rare-Earth Metal Organic Framework Materials for Hydrogen Storage. As the world grapples with the rising cost and diminishing reserves of fossil based fuels, there is an urgent need to resolve the issues surrounding the use of hydrogen as a fuel. Storage is one of the issues which limit full exploitation of hydrogen in this regard. While it can be stored in pressurized cylinders as a gas and as a liquid under cryogenic conditions, the volume restrictions associated with on-vehicle use requires that hydrogen be stored at densities higher that its liquid density. To this end various chemical storage methods are being explored. The high porosity and large surface area inside the open framework structures of metal-organic framework materials (MOFs) (Figure 1) make them suitable as molecular containers for trapping and storing small guest molecules such as hydrogen. MOFs which are based on rare-earth metals offer advantages such as the ability to trap and simultaneously detect the type of guest that is present in the pores by producing a light signal which is specific to the guest.

Figure 1: Diagrammatic representation of a Metal-Organic Framework Material. Note the open spaces in the MOF which can be used to trap and store H2.

We have used hydrothermal synthesis to prepare rare-earth containing MOFs whose structures display the potential for hydrogen storage.

H2(g)

Figure 2: Example of a rare-earth containing Metal Organic Framework Material made in Singh-Wilmot’s Group. The rare-earth metals are in pink. Note the pores (spaces) on the inside of the frame-like structure which can now be exploited for chemical storage.

Figure 3: Another MOF made in Singh-Wilmot’s group. Rare-Earths are shown in yellow and organic linkers in grey. The red balls in the spaces represent water molecules which were removed by heating and thereafter the frameworks remains stable up to 600 ⁰C.

Rare-earth Nanoclusters

In recent years investigations into the chemistry of rare earths and the synthesis of novel

complexes from them have boomed significantly. This is because scientists all over the world

have come to appreciate the unique intrinsic properties of these elements as well as realized

their true potential in various applications. Thus far rare earths have been employed in

organic synthesis, as luminescence sensors, catalysis and magnetic functional materials.

Although it is possible to reap many benefits of lanthanides from mononuclear complexes, it

has been shown that the unique properties of these ions are in fact enhanced when presented

in polynuclear clusters whose dimensions are in the nanometer range. Having polynuclear

lanthanide nanoclusters enhances the unique properties of the rare earth ions through intra or

intercluster metal-metal interactions and allows researchers to manipulate or tune the

behaviour of the clusters by varying the metal composition.

In addition, as a consequence of their small size, nanoclusters have the potential to give new

behaviour, with improved features which can lead to the development of new materials with

unique and exciting applications. For this reason there is a much activity in the synthesis and

characterization of Ln(III) polynuclear nanoclusters such as the one shown in figure 1 below

which consists of twenty-six dysprosium(III) ions. The literature has shown many other

reports on nanoclusters containing even more metal ions. However scientists are yet to develop

a rational synthetic route for producing these clusters and further, there is little data

available on the luminescent properties and metal-metal interactions in rare earth

nanoclusters. Such information in critical if we are to take advantage of the promised

exciting properties of these nanoclusters.

Example of a polynuclear rare earth complex.

Xiaojun Gu and Dongfeng Xue Inorg. Chem., 2007, 46 (8), pp 3212–3216

Our research goal is to study the dynamics of cluster formation by synthesizing and

characterizing novel rare earth nanoclusters. We also investigate the photophysical properties

including luminescence and decay dynamics in an effort to understand the behavior of

nanoclusters and to explore their potential applications as functional materials including as

precursors to the formation of MOFs.

Some examples of recently synthesised nanoclusters are given below.

Synthetic Scheme

OH

CH3

CH3

OEr-oxo/hydroxo

Er(ClO4)4 , C2H4(NH2)2pH 7.2

tetranuclear cluster nonanuclear cluster

 

 

 

 

 

 

 

Tetranuclear cluster

Nonanuclear cluster  

gen, hydrogen omittednn for clarity)  

 green‐erbium, black‐carbon, red‐oxygen, blue‐nitrogen. 

M.A. Singh-Wilmot et al., Polyhedron (2013), http://dx.doi.org/10.1016/j.poly.2013.01.028

Publications: Books: Holder, A.A.; Lewis-Alleyne, L.C.; Derveer, D.V.; Singh-Wilmot, M.A. Dipicolinic Acid, its Analogues and Derivatives: Aspects of their Coordination Chemistry,Nova Science Publishers, 2011. Refereed, research based publications: 1. Singh-Wilmot, M.A.; Sinclair, R. et al., Polyhedron, 2013, http://dx.doi.org/10.1016/j.poly.2013.01.028 2. Min, Z.; Singh-Wilmot, M.A.; Cahill, C.; Andrews, M.; Taylor, R. Isoreticular Ln-MOFs: Synthesis, Structures and Photoluminescence of a Family of 3-D Phenylcarboxylates, Eur. J. Inorg. Chem., 2012, 4419-4426.

3. Russell, F.A.; Mulabagal,V.; Thompson, D.R.; Singh-Wilmot, M.A.; Reynolds, W.F.; Nair, M.G.; Langer, V.; Reese, P.B. Novel Stemodin-Derived Analogues with Lipid Peroxidation, Cyclooxygenase Enzymes and Human Tumour Cell Proliferation Inhibitory Activities. Phytochemistry, 2011, 72, 2361-2368. 4. Bakir, M.; Green, O.; Singh-Wilmot, M.A. Synthesis, Spectroscopic and X-ray Crystallographic Analysis of Manganese Compounds of Di-2-pyridyl ketone thiophene-2-carboxylic acid hydrazone (dpktch): The Reaction of Mn(CO)5Br with dpktch. Journal of Molecular Structure, 2010, 967, 174-182. 5. Singh-Wilmot, M.A.; Kahwa, I.A.; White, A.J.P.; Williams, D.J.; Lough, A.J. Tunable Electronic Interactions in Small Lanthanide(III) Clusters: The Comparative Effects of OH- and O2- Supramolecular Glues on Europium(III)-to-Dysprosium(III) Energy Transfer. Polyhedron, 2010, 29, 270-279. 6. Singh-Wilmot, M.A.; Lough, A.J. Private Communication, Cambridge Structural Database (structure deposition), 1078. 7. Jarrett, S.; Brown, A.; Singh-Wilmot, M. The Synthesis, Structure and Reactivity of 1-Thioxotetrahydropyridazino[1,2-a][1,2,4]triazin-4(1H)-one. Heterocycles, 2009, 78, 11, 2755-2768. 8. Singh-Wilmot, M.A.; Richards-Johnson, R.U.; Dawkins, T.N.; Lough, A.J. Lanthanide(III) Coordination Polymers From the Exo-coordination of Na+: Syntheses, Structures, Luminescence and Decay Dynamics. Inorganica Chimica Acta, 2007, 360, 12, 3727-3733. 9. Bakir, M.; Lawerence, M.A.W.; Singh-Wilmot, M.A. Synthesis and Characterization of a of N,N,O-di-2-pyridyl ketone thiophene-2-carboxylic acid hydrazone (Cadmium-dichloro Compound η3-dpktch). The Structure of [CdCl2(η3-dpktch)]. Journal of Coordination Chemistry, 2007, 60, 22, 2385-2399. 10. Singh-Wilmot, M.A.; Kahwa, I.A.; Lough, A.J. Tetrakis( 2-2,6-diformyl-4-methylphenolato)tetra- 3-hydroxo-tetrakis[diaquaneodymium(III)] tetrakis(perchlorate) ethanol disolvate. Acta Crystallographica, 2006, E62, m113-m115.

11. Singh-Wilmot, M.A.; Kahwa, I.A.; Lough, A.J. Octaaquatetrakis( 2-2,6-diformyl-4-methylphenolato)tetra- 3-hydroxo-tetraneodymium(III) trifluoromethanesulfonate butanol disolvate tetrahydrate. Acta Crystallographica, 2005, E61, m970-m972.

12. Singh-Wilmot, M.A.; Kahwa, I.A.; Lough, A.J. Bis( -2,6-diformyl-4-methylphenolato)bis[bis(2,6-diformyl-4-methylphenolato)neodymium(III)]. Acta Crystallographica, 2005, E61, m1009-m1011.

13. Bakir, M.; Harewood, G.R.; Holder, A.; Hassan, I.; Dasgupta, T.P.; Maragh, P.; Singh-Wilmot, M. 5-[(4-Methylphenyl)diazenyl]salicylaldehyde. Acta Crystallographica, 2005, E61, o1611-o1613.

14. Bakir, M.; Clarke, S.A.; Hassan, I.; Lancashire, R.J.; Singh-Wilmot, M. trans-Bis(glycinato- 2N,O)copper(II) 4-bromophenol solvate. Acta Crystallographica, 2004, E60, m868-m870.