School of Physical Sciences

About

I graduated from the University of Bath in 2006 with an undergraduate masters degree in chemistry (Mchem, 1st class honours), before moving to Durham University to study for a PhD in the Department of Chemistry under the supervision of Dr. Andrés E. Goeta and Prof. Judith A. K. Howard (CBE, FRS).  My thesis described detailed structure-property correlations in switchable molecular materials using in-situ light irradiation, high-pressure and variable-temperature crystallographic investigations.  In 2010 I moved to the Laboratoire de Chimie de Coordination in Toulouse (LCC-CNRS) for a two year post-doctoral appointment under the supervision of Dr. Gábor Molnár and Dr. Azzedine Bousseksou in the Switchable Molecular Materials group.  During that time I investigated the physics of the spin crossover phenomenon under pressure (in collaboration with Prof. Philippe Guionneau at the Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB-CNRS)), and initiated a project concerned with novel applications for molecular materials as actuator devices.  In 2013 I returned to the University of Bath for a post-doctoral position under the supervision of Prof. Paul R. Raithby, before taking up the position of Lecturer in Chemistry at the University of Kent in 2015.

Contact Information

Address

Room 305A, Ingram Building

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Publications

Also view these in the Kent Academic Repository

Article
Robertson, K. et al. (2017). [Fe(Htrz)2(trz)](BF4) nanoparticle production in a milliscale segmented flow crystalliser. Chimica Oggi [Online] 35:19-22. Available at: http://www.teknoscienze.com/tks_article/fehtrz2trzbf4-nanoparticle-production-in-a-milli-scale-segmented-flow-crystalliser/.
Basri, A. et al. (2017). Bis-picolinamide Ruthenium(III) Dihalide Complexes: Dichloride-to-Diiodide Exchange Generates Single trans Isomers with High Potency and Cancer Cell Selectivity. Chemistry - A European Journal [Online] 23:6341-6356. Available at: https://doi.org/10.1002/chem.201605960.
Knichal, J. et al. (2016). An Iodine-Vapor-Induced Cyclization in a Crystalline Molecular Flask. Angewandte Chemie International Edition [Online] 55:5943-5946. Available at: http://dx.doi.org/10.1002/anie.201601525.
Shepherd, H. et al. (2016). Cooperative High-Temperature Spin Crossover Accompanied by a Highly Anisotropic Structural Distortion. European Journal of Inorganic Chemistry [Online]:1-5. Available at: http://www.dx.doi.org/10.1002/ejic.201600406.
Shepherd, H. et al. (2016). A High Pressure Investigation of the Order-Disorder Phase Transition and Accompanying Spin Crossover in [FeL12](ClO4)2 (L1 = 2,6-bis{3-methylpyrazol-1-yl}-pyrazine). Magnetochemistry [Online] 2:9. Available at: http://doi.org/10.3390/magnetochemistry2010009.
Showing 5 of 44 total publications in KAR. [See all in KAR]
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Research Interests

My principle research interests are concerned with the development of new smart materials that have useful properties (colour, size, magnetism etc.) that can change in response to an external influence (temperature, pH, stress etc.). I conduct both fundamental studies aimed at rationalisation of the underlying physical phenomena giving rise to the switchable properties, and also seek to develop these materials towards useful real-world applications.

Fundamental Studies

Molecular-based phase transition materials (PTMs) including spin-crossover systems (SCO), valence-tautomers (VT), and those that show switchable Jahn-Teller (JT) distortion undergo displacive phase transitions in which the motion of matter occurs in a continuous and cooperative manner throughout a material.  For example, in the case of SCO, a change occurs in the electronic configuration of certain (first row, d4 – d7) transition metal ions between high spin (HS) and low spin (LS) states in response to variation of thermodynamic parameters (e.g. temperature or pressure) or by the application of a perturbation such as magnetic field or light irradiation. This redistribution of electrons within the d-orbitals is accompanied by drastic structural modifications, most notable in the case of FeII (d6) ions, where switching between a t2g4eg2 HS configuration and a t2g6eg0 LS configuration results in a contraction of the Fe-Ligand bonds by c.a. 0.2 Å, a decrease in the molecular and macroscopic volume of the material, as well as a change in the magnetic properties from paramagnetic to diamagnetic. Furthermore, the SCO process can occur under ambient conditions, a great advantage for their many potential applications, for example in gas-sensing, displays, nano-thermometry and switchable photonic devices [1].

 

While SCO can occur in solution, it is an isolated molecular process representing a Boltzman distribution across the available spin states at a given temperature, resulting in extremely gradual conversion of the metal centres. Much more interesting from the point or view of application are cooperative spin transitions in the solid state, where all active sites are switched extremely abruptly, accompanied by hysteresis. It is increasingly observed that such cooperative behaviour stems from communication between iron centres as a result of long-range elastic interactions. For example, we have shown how the highly cooperative thermal SCO in a molecular FeII complex could be explained by an exceedingly unusual dynamic structural motion of the molecule, coupled to the stiffness of the lattice [2]. By understanding these structural effects I aim to rationalise and eventually control these useful properties in the solid state, from bulk-scale systems to nano-scale materials.

 

Towards Application

The ability to economically produce materials with increasingly useful properties is a defining factor in the pace of virtually all areas of technological innovation. As growth increases exponentially, the materials we rely on to construct and power the latest electronic and mechanical devices must become more efficient, more reliable and less expensive. While refining the properties of traditional materials can fulfil these requirements to a point, eventually we must seek new smart materials that can push the fundamental boundaries beyond those of existing systems.

During my time at the LCC-CNRS (Toulouse, France) I developed proof-of-concept actuator devices from molecular-based SCO materials that could convert changes in temperature and light irradiation into macroscopic motion.  Both single-crystal cantilevers [3] and SCO/polymer composite devices [4] were fabricated, with the latter able to be electrically addressed at room temperature, one of many vital requirements for a huge variety of potential applications.  I continue to develop new switchable materials as well as ways of incorporating these smart systems into new formats capable of integration with new technologies.

 

References

[1]           Spin Crossover at the Nanometre Scale, H. J. Shepherd, G. Molnár, W. Nicolazzi, L. Salmon, & A. Bousseksou, Eur. J. Inorg. Chem., 2013, 5-6, 653-661
[2]           Antagonism between Extreme Negative Linear Compression and Spin Crossover, H. J. Shepherd, T. Palamarciuc, P. Rosa, P. Guionneau, G. Molnár, J.-F. Létard & A. Bousseksou Angew. Chemie, 2012, 59, 3910-3914
[3]           Molecular Actuators Driven by Cooperative Spin-State Switching H. J. Shepherd I. A. Gural’skiy, C. M. Quintero, S. Tricard, L. Salmon, G. Molnár & A. Bousseksou, Nature Commun., 2013, 4, 2607, 1-9
[4]           Spin crossover composite materials for electrothermomechanical actuators I. A. Gural'skiy, C. M. Quintero, J. S. Costa, P. Demont, G. Molnár, L. Salmon, H. J. Shepherd & A. Bousseksou., J. Mater. Chem. C, 2014, 2,2949-2955

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Teaching

2015 - 2016

  • CH623: Transition Metal Organometallic Chemistry
  • PH700: Physics Research Project
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School of Physical Sciences, Ingram Building, University of Kent, Canterbury, Kent, CT2 7NH

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Last Updated: 09/03/2016