Professor Duncan Bruce

01904 324085
Email: duncan.bruce@york.ac.uk

Liquid Crystals and Materials Chemistry

Career Summary

Duncan is a Cumbrian who graduated from the University of Liverpool in 1981 and remained there for his PhD under the supervision of David Cole-Hamilton. His thesis concerned phosphine complexes of PtII and RhI as potential photocatalysts for the decomposition of water. In 1984, he took up a Temporary Lectureship in Inorganic Chemistry at the University of Sheffield and in 1986 was awarded a Royal Society Warren Research Fellowship, which he held there until 1991. He was then appointed Lecturer in Chemistry and was promoted Senior Lecturer in 1994, in which year he became co-director of the Sheffield Centre for Molecular Materials. In 1995, he was appointed Professor of Inorganic Chemistry at the University of Exeter. Following Exeter's disastrous closure of Chemistry in 2005, Duncan took up his present position as Professor of Materials Chemistry in York. He is immediate Past President of the Royal Society of Chemistry Materials Chemistry Division and Chair of the British Liquid Crystal Society.

His work has been recognised by various awards including: RSC's Tilden Prize (2010), Corday-Morgan Medal and Prize (1996) and Sir Edward Frankland Fellowship (1994/95), and the British Liquid Crystal Society's first Young Scientist prize (1990). He has held visiting positions in Australia, France, Italy, Japan and Taiwan.

Duncan has recently been editor on a new series of books with co-editors Dermot O'Hare and Richard Walton. The Inorganic Materials series consists of five volumes, each focusing on the physical properties a particular material.

Research Interests

The group has a range of interests, a common factor of all being liquid crystals. Full details of these can be found on the Group's website. Examples of current projects include:

Luminescent Liquid Crystals for OLED Applications: orthometallated 2-phenylpyridine derivatives of platinum(II) and iridium(III) have desirable photophysical properties as the triplet excited states lead to useful emission owing to spin-orbit coupling between the third-row transition metal and the ligand excited state. Therefore, complexes of this general type are of interest as the emissive component of OLED fabrications as both singlet and triplet states can be harvested.

However, if such complexes can also show liquid crystal properties then additional effects may be realised, for example enhanced carrier mobilities or polarised emission.
We have prepared two families of materials which show both triplet emission and liquid crystal properties, both based on platinum(II).

Two families of materials showing triplet emission - 

 
The complexes of the terdentate ligand are of particular note as the nature of the emissive state can be controlled as a consequence of the liquid crystal nature of the material. Thus, emission from the monomer state can be obtained and reversible interchanged with emission from the excimer.

V. N. Kozhevnikov, B. Donnio and D. W. Bruce, Angew. Chem. Int. Ed., 2008, 47, 6286-9.

A. Santoro, A. C. Whitwood, J. A. G. Williams, V. N. Kozhevnikov and D. W. Bruce Chem. Mater., 2009, 21, 3871-82.

Halogen-bonded Liquid Crystals: non-mesomorphic precursors bind to one another via a halogen bond between an electron-poor iodide and an electron-rich nitrogen. The resulting complexes are found to have liquid crystal properties.

The original work complexed iodopentafluorobenzene to an alkoxystilbazole, but later work addressed 2 : 1 complexes of stilbazoles with diiodotetrafluorobenzenes and diiodoperfluoroalkanes. Interestingly, such 2 : 1 complexes using 1,3-diiodotetrafluorobenzene showed a spontaneously chiral nematic phase even though there was no chirality in the complex.

 LC texture -
 

 Structural Diagram of halogen-bonded liquid crystal - Stilbazole Pentafluoroiodobenzene complex


X-ray structure of halogen-bonded liquid crystal -

We then addressed the strength of the halogen bond as a function of the acceptor strength of the iodide by preparing a series of complexes between fluoroiodobenzenes and DMAP, finding a linear correlation between the N...I separation and the number of fluorines, x.


graph - 

 Structural diagram of DMAP - Fluorinated Iodobenzene complex

Reproduced by kind permission of the ACS.

H. L. Nguyen, P. N. Horton, M. B. Hursthouse, A. C. Legon and D. W. Bruce, J. Am. Chem. Soc., 2004, 126, 16.

P. Metrangolo, C. Präsang, G. Resnati, R. Liantonio, A. C. Whitwood and D. W. Bruce, Chem. Commun. 2006, 3290.

D. W. Bruce, P. Metrangolo, F. Meyer, C. Präsang, G. Resnati and A. C. Whitwood New. J. Chem., 2008, 32, 477-82.

C. Präsang, A. C. Whitwood and D. W. Bruce, Chem. Commun., 2008, 2137-9.

C. Präsang, H. L. Nguyen, P. N. Horton, A. C. Whitwood and D. W. Bruce, Chem. Commun., 2008, 6164-6.

C. Präsang, A. C. Whitwood and D. W. Bruce, Cryst. Growth Des., 2009, 9, 5319-26.


Heterocyclic Liquid Crystals: using chemistry similar to that employed to prepare the 2-phenylpyridine ligands above, we have prepared a series of simple pyridine- and triazine-containing liquid crystals and, more interestingly, liquid-crystalline terpyridines. terpyridines without the fused cyclopentene rings show a chiral variant of the so-called B2 phase, while with the cyclopentene rings, nematic and smectic C phases are seen.

 Structural Diagram of Heterocyclic Liquid Crystals

V. N. Kozhevnikov, A. C. Whitwood and D. W. Bruce, Chem. Commun. 2007, 3826-8.

V. N. Kozhevnikov, S. J. Cowling, P. B. Karadakov and D. W. Bruce, J. Mater. Chem., 2008, 18, 1703-10.

Nanoparticle-doped, Nanostructured, Mesoporous Silicates: can be prepared by templating silicate formation around the liquid crystal phase of a metallosurfactant using a sol-gel methodology. We have shown that surfactant ruthenium bipyridine complexes can do this and that the RuO2-doped materials formed are good oxidation catalysts and very good hydrogenation catalysts when the particles are reduced to Ru0. However, the Ru surfactants appear to be fairly unique as many other metallosurfactants that we synthesised proved to be ineffective templating agents. Therefore we sought an alternative approach.

What we did was to use the mesophase of neutral, ethylene oxide surfactants (e.g. C12EO8) who hexagonal phase was prepared with an aqueous solution of the Group 1 metal salt of an inert metallate anion (e.g. K2[PtCl4] or the Group 1 salt of an EDTA complex (e.g. Na[Fe(EDTA)]). Sol-gel condensation of Si(OMe)4 followed by calcination led to silicates containing a dispersion of metal nanoparticles. Porous silicates containing bimetallic nanoparticles were also made in this way.

Structure and electron-microsope image of Nanoparticle-doped, Nanostructured, Mesoporous Silicates
Ir-containing silicates prepared by the new methodology. Reproduced by kind permission of the Royal Society of Chemistry.

M. J. Danks, H. B. Jervis, M. Nowotny, W. Zhou, T. A. Maschmeyer and D. W. Bruce, Catal. Lett., 2002, 82, 95.

N. C. King, C. Dickson, W. Zhou and D. W. Bruce, Dalton Trans., 2005, 1047.

N. C. King, R. A. Blackley, W. Zhou and D. W. Bruce, Chem. Commun., 2006, 3411.

N. C. King, R. A. Blackley, M. L. Wears, D. M. Newman, W. Zhou and D. W. Bruce, Chem. Commun., 2006, 3414.