Professor David L. Davies

Professor in Inorganic Chemistry
Dr David L. Davies

 

 

 

 

Tel: +44 (0)116 252 2092
Email: dld3@le.ac.uk

Personal details

There is an need to increase efficiency and reduce the waste and environmental impact of chemical synthesis. My research is focused on designing new synthetic methods to convert CH bonds into C-C C-N and C-O bonds.

Our approach is through mechanistic understanding. In addition, we study the preparation of new luminescent compounds for several different applications.

Awards received

  • University Teaching Fellowship, June 2009
  • Leverhulme Trust Study Abroad Fellowship, August 2011 to January 2012

Collaborators

Publications

C-H activation

Room-temperature cyclometallation of amines, imines and oxazolines with [MCl2Cp* ]2 (M = Rh, Ir) and [RuCl2(p- cymene)]2 D.L. Davies, O. Al-Duaij, J. Fawcett, M. Giardiello, S.T. Hilton, and D.R. Russell, Dalton Trans., 2003, 4132-4138.

Computational Study of the Mechanism of Cyclometallation by Palladium Acetate D.L. Davies, S.M.A. Donald, and S.A. Macgregor, J. Amer. Chem. Soc., 2005, 127, 13754-55.

Electrophilic C-H Activation at {Cp*Ir}: Ancillary-Ligand Control of the Mechanism of C-H Activation  D.L. Davies, S.M.A. Donald, O. Al-Duaij, S.A. Macgregor, and M. Polleth, J. Am. Chem. Soc., 2006, 128, 4210-4211.

Mechanisms of C-H bond activation: rich synergy between computation and experiment: Y. Boutadla, D. L. Davies, S. A. Macgregor and A. I. Poblador-Bahamonde, Dalton Trans, 2009, 5820-5831.

Mechanistic Study of Acetate-Assisted C-H Activation of 2-Substituted Pyridines with [MCl2CP*](2) (M = Rh, Ir) and [RuCl2(p-cymene)](2). Y. Boutadla, O. Al-Duaij, D.L. Davies, G.A. Griffith, and K. Singh, Organometallics, 2009, 28, 433-440.

The Scope of Ambiphilic Acetate-Assisted Cyclometallation with Half-Sandwich Complexes of Iridium, Rhodium and Ruthenium: Y. Boutadla, D. L. Davies, R. C. Jones and K. Singh, Chem. Eur. J., 2011, 17, 3438-3448.

Alkyne insertion into cyclometallated pyrazole and imine complexes of iridium, rhodium and ruthenium; relevance to catalytic formation of carbo- and heterocycles: Y. Boutadla, D. L. Davies, O. Al-Duaij, J. Fawcett, R. C. Jones and K. Singh, Dalton Trans, 2010, 39, 10447-10457.

Reactions of Cyclometalated Oxazoline Half-Sandwich Complexes of Iridium and Ruthenium with Alkynes and CO: D. L. Davies, O. Al-Duaij, J. Fawcett and K. Singh, Organometallics, 2010 29, 1413-1420.

Luminescent complexes

Tuning emission wavelength and redox properties through position of the substituent in iridium(III) cyclometallated complexes: D. L. Davies, M. P. Lowe, K. S. Ryder, K. Singh and S. Singh, Dalton Trans, 2011 40, 1028-1030.

Luminescent iridium complexes for detection of molybdate: C. E. Castillo, D. L. Davies, A.-K. D. Klair, K. Singh and S. Singh, Dalton Trans, 2012, 41, 628-635.

Research

C-H activation

Metal catalysed C-H activation followed by C-C bond formation is potentially extremely efficient in terms of atom economy and chemoselectivity and is thus a very desirable transformation from a Green Chemistry point of view. Currently the most successful strategy involves cyclometallation reactions. A few years ago, we discovered an acetate-assisted C-H activation which provides a very mild (room temperature) route to cyclometallated half-sandwich complexes.

In collaboration with a computational chemistry group (Prof S. A. Macgregor, Heriot Watt University), we examined the mechanism. Our initial results on cyclometallation with palladium acetate showed that the reaction goes by an electrophilic like activation, however, this occurs via an agostic intermediate rather than the traditionally assumed Wheland intermediate, with considerable intramolecular hydrogen bonding to a coordinated acetate involving a 6-membered transition state. We have subsequently shown that a similar mechanism operates for formation of Cp*Ir cyclometallated complexes (see fig. below for calculated transition states).

Asymmetric Catalysis

This is the first electrophilic C-H activation for iridium and the first which doesn’t proceed via oxidative addition for a Cp*iridium species. These cyclometallations are examples of a new mechanism for C-H activation involving simultaneous activation by a Lewis acidic metal (agostic interaction) and a basic ligand (hydrogen bond) which operate in a synergistic manner to provide a low energy pathway to C-H activation. We have termed this Ambiphilic Metal Ligand Activation. We have now shown that this process can also be used to achieve sp3 CH activation. We have also surveyed the types of directing groups that can be used.

AMLA CHactivation can be incorporated into a catalytic cycle to achieve catalytic CH functionalisation. We have studied the mechanisms of these processes and have identified intermediates from CH activation followed by alkyne insertion.

    Luminescent complexes

    X-rayCyclometallated iridium complexes [Ir(C~N)2(XY)]n+ (C~N = cyclometallated ligand, XY = bidentate ligand, n = 0,1] have attracted a lot of attention due to their interesting luminescent properties. The fluorescent properties of the complexes, high efficiency, due to spin orbit coupling, relatively long–lived emission and large Stokes shift and the tuneability of these properties by ligand modification make them attractive for a variety of appllications e.g. in OLEDs, solar cells, sensors, and biological imaging.

    The main goal of our work is to explore the use of new ligands and different substituents to control the physical properties (solubility etc) and luminescent properties (emission wavelength, lifetime and quantum yield) of the complexes. We have recently shown that the emission wavelength can be tuned by changing the position of substituents on the cyclometallated phenyl.We have also demonstrated the use of these types of complex in sensing molybdate.

    This work is done in collaboration with Dr A. Duhme Klair, York, Prof Mike Wolf UBC, Vancouver and Dr F Lelj, Potenza.

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    Contact Details

    Department of Chemistry
    University of Leicester
    Leicester, LE1 7RH, UK

    Email: chemistry@le.ac.uk

    Tel: [+44] (0)116 252 2100

    Fax: [+44] (0)116 252 3789

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