Our general interests lie in the area of coordination chemistry, especially of the transition metal complexes in high oxidation states; the preparation of new complexes and their characterisation both in the solid state and in solution; and their application as oxidation catalysts for useful organic oxidations.
More specific interests and aims are:
1. Metal oxo complexes
2. Metal peroxo complexes
3. New catalysts for bleaching
4.Studies in Raman spectroscopy and in mineral chemistry
The synthesis of new transition metal oxo (O2-) complexes, particularly of those metals which show versatility in their oxidation states, e. g. ruthenium, osmium, rhenium, chromium and manganese. We make these, characterise them in the solid state (where appropriate) by single crystal X-ray studies, Raman, infrared, ESR and solid state NMR spectroscopy. We then use Raman and multinuclear NMR, when possible, to study the structures in solution, in which environment they normally operate as oxidation catalysts.
(NMO is N -methylmorphholine-N -oxide)
Such complexes are then assessed for their oxidation capabilities as metal-mediated oxidants, using in the first instance simple organic substrates such as benzyl alcohol, cyclohexanol or cyclo-octene. These oxidations are carried out both stoichiometrically (i. e. on their own) and catalytically with an appropriate and preferably environmentally acceptable co oxidant, e. g. dioxygen, ozone, hydrogen peroxide, tert-butylhydroperoxide, persulfate etc.
(NMM is N- methylmorpholine)
The synthesis of new peroxo (O22-) complexes, mainly of metals in their highest oxidation states (e. g. molybdenum(VI), tungsten(VI), vanadium(V)). These are often effective ligand-mediated oxidation catalysts with hydrogen peroxide or tert-butylhydroperoxide as co oxidants. The structures of the solid complexes and their solutions are studied in the same way as for oxo complexes above.
The development of new, environmentally acceptable catalysts for bleaching of fabrics under normal domestic laundry conditions by hydrogen peroxide or inorganic peroxy-salts is important because, if hydrogen peroxide can be activated by such a catalyst to work at a lower temperature than that normal used in normal bleaching, much energy could be saved. We are actively concerned, with the collaboration of Professor Michael Spiro, in such development, and also with a study of the mechanisms whereby the oxidative bleaching of dyes modelling those normally found in fabric stains (e. g. alizarin, phenolphthalein, crocetin, malvidin, methyl orange) by hydrogen peroxide occurs both without and with catalysts.
Raman spectroscopy is a technique too infrequently used by chemists, in our biased view. Because water (and glass) have weak Raman spectra, it is easy to study the Raman spectra of species in aqueous solutions in simple glass cells, procedures difficult for infrared work. We gain information as to the structures of our catalysts in aqueous solution, in which media they normally effect their catalysis. We are also involved in SERS (surface-enhanced Raman spectroscopy).
A long-standing interest has been in minerals - nature's chemistry - and recently, in collaboration with Mike Mingos, we have synthesised minerals using microwave techniques and deuterated them, where they contain protons; such deuteration helps in assigning their vibrational modes.