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Professor Vickie McKee |
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Our interests are primarily focused on synthetic and structural aspects of coordination chemistry, with particular emphasis on the use of geometric factors to control metal-metal interactions and other properties in bi- or polymetallic systems. These find potential applications in fields ranging from bioinorganic chemistry to surface and solid state chemistry. Some recent work in the areas of transition metal macrocyclic chemistry, manganese bioinorganic chemistry, azacryptands and X-ray crystallography is briefly outlined below, followed by some recent publications and links to some interesting bits of information. There is also almost a portrait and an actual photo.
 A
tetracopper(II) complex with a central m4-hydroxo
group. |
We have developed synthetic routes
to tetranucleating complexes in which the bridged metal ions are held at
ca. 3Å apart and have characterised a number of tetranuclear complexes
of copper, nickel, cobalt and manganese. Octacopper complexes have also
been synthesised and some aspects of the Cu8 complexes suggest
the onset of some bulk electronic structure.
Current work is directed towards:
Ligands with different donors and/or geometry at some of the metal-binding sites, which should promote the synthesis of mixed valence complexes with very different redox activity at the different sites. Larger and more flexible arrays.
A tetranickel thiophenolate complex [Ni4(LS)(OH)(OAC)3(HOAc)] An octanuclear copper complex, {[Cu4(L)O]2}4+ A heteronuclear complex , {[Cu2Ni2(L)O(OAc][Ni2(dfmp)(OAc)(OH)3]} - shown in Jmol |
 
Geometrically-controlled redox states in manganese complexes |
We have designed, synthesised and
characterised a series of tetramanganese complexes as early models for
the oxygen evolving centre of Photosystem II, including the first example
of a Mn4O4 cubane. Macrocyclic or polydentate ligands
have enabled us to maintain the control over nuclearity which is often
missing in other systems, however, the accessible oxidation levels of the
clusters are low (from MnII4 to MnIII4).
Current objectives include the development of higher oxidation level and
electroactive complexes.
Control of redox potential is an essential feature of manganese metalloproteins. Much of the fine tuning of redox properties appears to be achieved by the ability of the protein to impose particular geometric constraints on the metal centres. Recently we have been investigating the subtle relationship between coordination geometry and redox level in complexes of manganese and other transition metals. The cations shown opposite illustrate the correlations emerging from this study. Each of the ligands supplies a six-coordinate, fac (imine)3(phenolate)3 site but the "aerobic" oxidation level adopted by the manganese complexes depends on the detailed geometry imposed on the metal ion (+II for the top complex, +III for the middle and +IV for the lower one). Data such as these will enable us to synthesise high-valent and mixed-valence complexes where the redox potential of each site is controlled by "designer distortions". CHIME version of a tetranuclear MnII2MnIII2 complex. In related work, in collaboration with Dr M. McCann we have investigated the structures and possible catalase activity of a wide range of manganese complexes. Our laboratory is part of the COST D21 working group "Synthesis and Reactivity Studies of Biomimetic Model Complexes for Active Sites of Manganese-containing Enzymes". |
 An
SiF62- anion encapsulated within a cryptand ligand. |
A series of average valence Cu(1.5)2 cryptates has been characterised and these serve as spectroscopic models for aspects of the recently described binuclear average-valence Cu2 site in Cytochrome c Oxidase and some other copper proteins. Crystallographic work has defined a Cu-Cu bond of about 2.4 Å in the average valence complexes and demonstrated that this is significantly shorter than in the analogous dicopper(I) complexes. The unusual redox properties of this arrangement are controlled principally by geometric constraints within the cryptand ligand. Other work in this area includes characterisation of cryptate hosts for anions (an area of current environmental concern) and the development of hosts for MRI contrast agents. Click on the links below for CHIME versions of:
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Single crystal X-ray crystallographic studies underpin each of the areas outlined above. In addition to work using the low temperature Bruker SMART system in our X-ray laboratory, we make occasional use of the synchrotron line 9.8 at the Daresbury Synchrotron Radiation Source SRS.The facilities for X-ray diffraction and the status of the diffractometers are described on the X-ray diffraction webpage.
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Dinuclear Complexes of a Pseudocalixarene Macrocycle: Structural Consequences of Intramolecular Hydrogen Bonding.
J. Barreira Fontecha, S. Goetz and V. McKee. Dalton Trans., 2005, 923-929.
V. McKee, J. Nelson and R.M. Town. Chem. Soc. Rev., 32, 2003, 309-325.
Di-
Tri and Tetracopper(II) Complexes of a Pseudocalixarene Macrocycle.
J. Barreira Fontecha, S. Goetz and V. McKee,
Angew. Chemie, Int. Ed. Engl., 2002, 41, 4554-4556.
Site-selectivity
in a Heterotetranuclear Macrocyclic Complex.
S. Cromie, F. Launay and V. McKee, Chem. Commun.,
2001, 1918-1919.
Protonated
azacryptate hosts for nitrate and perchlorate.
M.J. Hynes, B. Maubert, V. McKee, R.M. Town and
J. Nelson, J. Chem. Soc., Dalton Trans., 2000, 2853 - 2859.
Geometric
Control of Redox Level in Tetranuclear Manganese and Cobalt Systems.
J. McCrea, V. McKee, T. Metcalfe, S. S. Tandon
and J. Wikaira, Inorg. Chim. Acta, (Special Volume in Honour of Prof. S.
J. Lippard), 297, 2000, 220-230.
Some useful links to:
Nick Kim's Cartoon site
Very pretty designer snowflakes
The Royal Society of Chemistry (RSC)
The British Crystallographic Association (BCA)
The International Union of Crystallography (IUCr)
RSC Macrocycles and Supramolecular Chemistry Group
RSC Coordination Chemistry Group
ChemJobs.net
ChemWeb
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Last Updated 15 January 2007 v.mckee@lboro.ac.uk |
