Kilian Research Group
Research activities in our newly established group are centred on design and synthesis of organophosphorus and Group 15 organoelement compounds. We synthesize new compounds for various practical applications, such as spin labels. Novel species are also of academic interest, we are very interested in exploration of new bonding, structure and reactivity and in synthetic methodology development. We also develop new (more efficient) syntheses of established compounds, such as those used as plastic additives.
Our typical synthetic project involves:
1. Synthetic targets with specific characteristics relevant to prospective use are proposed, often with the help of computational chemistry.
2. Synthetic strategy towards the target compound is devised and tested. Sometimes several synthetic approaches have to be tested to achieve the goal set out initially, or the target has to be modified to become achievable.
3. The desired characteristics of the target compounds (sometimes predicted computationally) are verified experimentally.
characterization results are fed back into synthesis, suitable structural
modifications leading to improved characteristics are proposed and necessary
modifications are introduced to the synthetic pathway.
Unusual (and therefore interesting) structural features, properties or reactivity crop up sometimes during the experimental work. Exploitation of these unforeseen results is an important part of (our) scientific activity.
The four major areas of our research are:
Radicals are usually observed as rather short-lived intermediates. In main group chemistry they can be stabilised to the extent that they can even be isolated in crystalline form. We have begun our investigations into stable phosphorus centred radicals recently; of our particular interest are radicals with potential to be used in spin labelling. Spin labels are artificial paramagnetic probes introduced into the system (for example large biomolecules such as membrane proteins) in order to make it ‘visible’ by Electron Paramagnetic Spectroscopy (EPR), which is a particularly sensitive resonance spectroscopy technique. New spin labels with favourable paramagnetic characteristics are extremely desirable since they can improve the capabilities and scope of those established, as well as several newly emerging and rapidly developing magnetic resonance methods, such as DNP (Dynamic Nuclear Polarization, NMR enhancement method), High Field and Pulsed EPR (used in long range distance measurements, and dynamic processes investigations in biomolecules), as well as EPR Imaging (medicinal imaging complementary e.g. to the more familiar NMR imaging - MRI). As the need for new classes of spin labels is growing, our activities will be even more strongly linked to spin label chemistry in the near future.
Phosphinyl radicals have large π-character of their SOMO (Singly Occupied Molecular Orbital) and therefore large hyperfine anisotropy, which makes them highly orientationally sensitive spin labels.
Phosphoranyl radicals can have extremely large hyperfine coupling, which generates huge interest in their development as polarizing agents in Dynamic Nuclear Polarization techniques.
We have a long-term interest in chemistry of peri-substituted (i.e., 1,8-disubstituted) naphthalenes and related molecular frameworks. The special geometry in these systems forces the two substituents into a close proximity, making the attractive interaction (i.e., bond) between them highly favourable as it minimises the steric strain. This results in unusual reactivity, bonding, structure and properties. Understanding the reactivity and development of synthetic methodology of multiply functionalised organophosphorus molecules is important for practical applications of these and related compounds (for example in catalysis). Unusual bonding, structure and properties are often observed in peri-substituted naphthalenes, and are of fundamental interest.
Many phosphorus chemicals (bulk and fine) are made from white phosphorus, but indirectly via phosphorus trichloride. Manufacture of PCl3 requires chlorine gas, which is highly toxic and corrosive, possesses high environmental risk and is ‘energy expensive’. Halogenation of white phosphorus to PCl3 serves essentially as a means of reactivity moderating and often no halogen is retained in the resulting products. Therefore, it is highly desirable to search for other means of moderating the reactivity of white phosphorus in order to achieve energy and atom efficient transformations into high value chemicals, without the formation of halide waste. Ideally the new reactivity moderators replacing halogenation will be inexpensive, non-toxic, highly specific and highly efficient (therefore only catalytic amounts will be needed).
P-C bond forming reactions are central to syntheses of tertiary phosphines, which in turn are essential components of many transition metal complexes used as catalysts in many organic transformations. Established P-C bond forming strategies require specifically activated organic substrates to achieve the required reactivity when connecting them to the phosphorus atom regiospecifically. The aim of our research in this area is to develop new synthetic routes to make a variety of tertiary phosphines from non-activated substrates, mainly aromates.