Much of the research in our group is inspired by biology. We are currently designing some novel biomimetic oxidation catalysts based on high valent iron(IV)-oxo or iron(III)-peroxo moieties which incorporate a hydrophobic channel. The aim is to catalyse the 1-oxygenation of n-alkanes within a restricted hydrophobic environment. Our design strategy is based on creation of a binding/activating site for a metal ion, a binding site for the oxygen transfer agent (oxide/hydroperoxide) (urea or amide motif) and a hydrophobic region/channel (attachment of long chain alkyl or perfluorous tail) for the n-alkane.

We are currently focussing our research on iron(III)-OOH complexes of 6-substituted derivatives of TPA (tris(2-pyridylmethyl)amine) (see example below).

We are also interested in the mechanisms of ligand replacement reactions at low symmetry/non-standard metal coordination geometries including those created within metal clusters. In a recent kinetic study of water exchange at 9-coordinated Mo and W in triangular acetate-bridged clusters a novel and unexpected mechanistic changeover from strongly dissociative (Mo) to associative (W) was found between two structurally identical cluster derivatives (ref. 2 below).

SELECTED RECENT PUBLICATIONS

1. Kinetics of the reaction of mer-tris(picolinato) iron(III) with hydrogen peroxide in pyridine: role of hydroxyl radicals in subsequent catalytic oxygenation of cyclohexane to the ketone. D.T. Richens, S.L. Jain, A.C. Gale. Inorg. React. Mech. 2006, 6, in print.
2. Distinct water-exchange mechanisms for trinuclear transition-metal clusters. J.R. Houston, D.T. Richens, W.H. Casey. Inorg. Chem. 2006, 45, 7962-7967.
3. Redox Chemistry of the d⁶ Acetato-bridged Clusters [M^IV₃(µ₃-O)_n(O₂CCH₃)₆(H₂O)₃]²⁺ (M = Mo, W, n = 1, 2): Reversible Redox Between Mono-µ₃-oxo d⁸ M^III,III,IV and d⁹ M^III₃ Forms. G. Powell, D.T. Richens. Dalton Trans. 2006, 2959-2963.
4. Structure-Property Relationships in Polynuclear µ-O Bridged Aqua Clusters; Effect of M-µO bond Covalency. D.T. Richens. Comm. Inorg. Chem. 2005, 26, 217-232.
5. Ligand Substitution Reactions at Inorganic Centers. D. T. Richens. Chemical Reviews 2005, 105, 1961-2002.
6. Metal Aqua Ions. S.F. Lincoln, D.T. Richens, A.G. Sykes. in Comprehensive Co-ordination Chemistry II, eds. J.A. McCleverty, T.J. Meyer. Elsevier: Amsterdam, 2004, 1.25, 515-555.
7. Syntheses and Characterization of Two Dioxygen Reactive Dinuclear Macrocyclic Schiff-base Copper(I) Complexes. D. Utz, F.W. Heinemann, F. Hampel, D.T. Richens, S. Schindler. Inorg. Chem. 2003, 42, 1430–1436.