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 to 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 served as President of the Royal Society of Chemistry Materials Division from 2006-2009, Chair of the British Liquid Crystal Society from 2009-2011 and is currently an elected member of RSC Council and Chair of its Audit Committee.

His work has been recognised by various awards including British Liquid Crystal Society's first Young Scientist prize (1990) and the RSC's Peter Day Award (2014), Tilden Prize (2010), Corday-Morgan Medal and Prize (1996) and Sir Edward Frankland Fellowship (1994/95). He has held visiting positions in Argentina, Australia, Chile, France, Japan, Italy and Taiwan.

 

Research Interests

The group has a range of interests, a common factor of all being liquid crystals. Examples of current projects include:

Halogen-bonded Liquid Crystals and Co-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.

  Reproduced by kind permission of the ACS

liquid crystals         Structures of halogen bonded liquid crystals

 

A full and systematic study of some 90 halogen-bonded liquid crystals was published in collaboration with the Milan group, while more recently we have described liquid crystals arising from the complexation of molecular iodine to alkoxystilbazoles.

stilbazole iodostilbene complex

 

stilbazole iodine complex 1

 

stilbazole iodine complex 2

 

Led by Peter Karadakov, we have undertaken theoretical studies of some aspects of halogen bonding, including a study of the weak attractive interactions between halogen bond donors and rare gases.

 

halogen bonding orbital diagram

 Reproduced by kind permission of the ACS

In a detailed study of co-crystals of 4-halotetrafluorophenol with secondary and tertiary amines, it was found that the phenate anion in the crystal had a delocalised structure meaning that the phenolic oxygen formed a double bond to the ring carbon (borne out by calculation at the MP2 level of theory). The two sp2 orbitals then formed either two hydrogen bonds or one halogen and one hydrogen bond, depending on the number of acidic hydrogen atoms available. Further, in some cases where there were two, in-plane hydrogen bonds to the sp2 orbitals on oxygen, there was, in addition, a halogen bond from a neighbouring iodine to oxygen through the C=O ∏-bond. This study has significance in describing synthetic models for halogen bonding in biological systems.

 phenate amine complex 

oxygen iodine halogen bond phenate amide complex

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 families of materials which show both triplet emission and liquid crystal properties, based on platinum(II) and iridium (III) and with substantial solution quantum yields. The complexes of the terdentate ligand are of 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.‌

phenyl pyridine Pt complex 1phenyl pyridine Pt complex 2 phenyl pyridine Ir complex

 

 Ionic Liquids:  With John Slattery, we are currently undertaking two main projects:

(i) Reactivity in Liquid-crystalline Ionic Liquids (LC-ILs): Here we are synthesising new and established LC-ILs with a range of mesophase structures with a view to using them as solvents to influence the outcome of chemical reactions. The work combines my expertise in liquid crystal synthesis (not least of ionic species) with John Slattery's knowledge of ionic liquids. The research is predicated on the understanding of the bulk anisotropic environment of liquids and the fact that this can exert an influence on the transition states formed during a reaction, hence influencing the reaction outcome. Examples of solvents we have used are given below: some are well known or have been reported previously, while others are new (Y. Gao, J. M. Slattery and D. W. Bruce, New J. Chem., 2011, 35, 2910-2918).

 Ionic liquid structures

We have studied different pericyclic reactions (Diels-Alder reactions, Claisen and aza-Claisen rearrangements) in these solvents and have very good evidence for liquid crystal effects on the rate and/or stereochemical outcomes of reactions. Our understanding of these effects is complemented by a collaboration with Zé Nuno Canongia Lopes and Katrina Shimizu in Lisbon, Portugal who undertake atomistic molecular-dynamics simulations, in particular on ionic liquid systems. Publications are currently being prepared.

Liquid crystal texture

 

  (ii) The Surface Structure of Ionic Liquids: This work is funded currently by an EPSRC-NSF award to the York group, Professor Ken McKendrick and Dr Matthew Costen at Heriot Watt University, and Professor Tim Minton at Montana State University, USA, with additional collaboration involving Professor George Schatz from Northwestern University, also in the USA. The project involves the dynamic scattering of gases from the surface of the ionic liquids in order to probe their composition. O(3P) atoms are used as reactive probes of the surface structure and dynamics. The experiments at Heriot Watt and Montana utilise very different O(3P) atom energies, allowing for different chemical groupings to be sampled. Initial studies1 have pointed to the concentration of alkyl chains at the surfaces in pure materials and the work is now extending to a study of mixtures and also liquid-crystalline systems using a very wide range of physico-chemical techniques.

Probe abstract

‌1 M. A. Tesa-Serrate, B. C. Marshall, E. J. Smoll, Jr., S. M. Purcell, M. L. Costen, J. M. Slattery, T. K. Minton and K. G. McKendrick, J. Phys. Chem. C, 2015, 119 , 5491–5505; C. Waring, P. A. J. Bagot, J. M. Slattery, M. L. Costen and K. G. McKendrick, J Phys Chem A, 2010, 114, 4896-4904; C. Waring, P. A. J. Bagot, J. M. Slattery, M. L. Costen and K. G. McKendrick, J Phys Chem Lett, 2010, 1, 429-433; B. H. Wu, J. M. Zhang, T. K. Minton, K. G. McKendrick, J. M. Slattery, S. Yockel and G. C. Schatz, J Phys Chem C, 2010, 114, 4015-4027.

Recent References

Halogen Bonding:

A. Takemura, L. J. McAllister, S. Hart, N. E. Pridmore, P. B. Karadakov, A. C. Whitwood and D. W. Bruce, Chem. Eur. J., 2014. DOI: 10.1002/chem.201402128.

L. J. McAllister, C. Präsang, J. P.-W. Wong, R. J. Thatcher, A. C. Whitwood, B. Donnio, P. O'Brien, P. B. Karadakov and D. W. Bruce, Chem. Commun., 2013, 49, 3946.

L. J. McAllister, D. W. Bruce and P. B. Karadakov, J. Phys. Chem A, 2012, 116, 10621.

D. W. Bruce,P. Metrangolo, F. Meyer, T. Pilati, C. Präsang, G. Resnati, G. Terraneo, S. G. Wainwright and A. C. Whitwood, Chem. Eur. J., 2010, 16, 9511.

Luminescent Liquid Crystals:

M. Spencer, A. Santoro, A. Díez, P. R. Murray, G. R. Freeman, J. Torroba, A. C. Whitwood, L. J. Yellowlees, J. A. G. Williams and D. W. Bruce, Dalton Trans., 2012, 41, 14244.

A. M. Prokhorov, A. Santoro, J. A. G. Williams and D. W. Bruce, Angew. Chem. Int. Ed., 2012, 51, 95.

A. Santoro, A. M. Prokhorov, V. N. Kozhevnikov, A. C. Whitwood, B. Donnio, J. A. G. Williams and D. W. Bruce, J. Am. Chem. Soc., 2011, 133, 5248.