Volatile organic solvents are the normal media for the industrial synthesis of organic chemicals (petrochemical and pharmaceutical), with a current world-wide usage estimated at £4,000,000,000 p.a. However, their environmental impact is significant, and the Montreal Protocol has resulted in a compelling need to re-evaluate many chemical processes that have proved otherwise satisfactory for much of this century. A conspicuous local example is the closure of one of the DuPont Hypalon® plants, which had been operating with chlorinated hydrocarbon solvents: ionic liquids are involatile. The principal aim of our work is to explore, develop and understand the role of ionic liquids as media for synthetic organic chemistry (including polymer chemistry and petrochemical processes), such that current commercial processes using conventional molecular organic solvents may be replaced by clean processes using ionic liquid technology, and so that new processes may be developed. We have created a unique centre, QUILL, to pursue these goals.
QUILL is unique in the world in existing to prevent pollution being created in the first place; it thus investigates, develops and operates a green (sustainable) strategy for the chemical industry. Its 16 Members are drawn from all sectors of the chemical industry and are located in nine countries and on four continents. The scope of the research is so large that the industry partners cannot afford to develop it individually; QUILL provides the perfect mechanism for industry-industry collaboration with an academic nexus. QUILL is demonstrably leading the world in ionic liquids for green chemistry.
The field of ionic liquids, the focus of QUILL's research programmes, is currently one of the "hottest topics" in scientific research today, with the number of publications more than doubling every 2 years. In 1994, only 20 papers per year were published in this field; with 2,165 papers published in the past 10 years, and with more than half (1,288) appearing in the past 2 years, this staggering growth can be rationalised by the formation of QUILL. These papers have involved 3,342 authors, 57 countries, 290 journals, and 745 institutions, and yet QUILL is ranked number one in citations on the ISI Essential Science Indicator (http://www.esi-topics.com/ionic-liquids/interviews/queens-univ-belfast.html), and its staff are found in the top three in the world in all the indices.
The research strategy and targets for the Centre are set (at six-monthly intervals) by the Industrial Advisory Board, consisting of one representative from each Member company. The research is fully interactive between the Members and the QUILL Centre, and involves the two-way exchange of researchers. The cynosure of the activity is in developing novel (patentable) research, and scaling it up to semi-pilot-plant scale. This activity has attracted additional support from the EPSRC, DTI and the EC. The Centre involves cross-faculty cooperation, drawing together staff from Chemistry, Chemical Engineering and Physics.
The chemist is comfortable and familiar with intramolecular bonding; our advanced knowledge of synthetic chemistry (which could almost be considered as the raison d’être of the chemist) is constructed around our understanding of the essential principles of covalent bonding. Less well-known and acceptable are the concepts of intermolecular bonds between molecules and ions (even the field of supramolecular chemistry has only just established itself), and our understanding of the factors which control crystal habit and morphology is rudimentary. The chemist, in designing molecules, rarely turns his attention to the crystalline form which that molecule will adopt in the solid state. The crystal form is usually a matter of serendipity; the ubiquitous occurrence of polymorphism is either ignored or treated as a problem beyond control. However, the recent litigation between Novopharm and Glaxo concerning the drug Zantac™ has focussed attention on polymorphism in a way in which only a multi-billion dollar court case can: the cynosure of this action is the polymorphism of ranitidinium chloride, the active ingredient. Crystal engineering is a field in its infancy; it is at the interface between a number of demanding disciplines, and has all the challenge and excitement expected of interdisciplinary research. We treat the hydrogen bond as a synthetic vector for granting topological control over crystalline form, and hence control over such crucial physical phenomena as optical properties, thermal stability, solubility, colour, conductivity, crystal habit, and mechanical strength. The significance of this area to industry and academia cannot be overstated. We were able to show that recent claims that “conventional hydrogen bonds may not be necessary for high efficiency and fidelity in DNA synthesis” and that “DNA polymerase can exert high fidelity even when a base pair completely lacks conventional hydrogen bonds” are in error. We have also demonstrated (see, for example, Figure 2) that the van der Waals radius is a very poor descriptor for detecting hydrogen bonds in the solid state.
The Dunhuang Diamond Sutra is a focus for the conservation of Chinese document collections held in London, Paris and St. Petersburg. The paper of the Dunhuang Diamond Sutra (see Figure 3) - the world’s oldest, dated, printed book - is dyed yellow with an extract believed to contain the alkaloid berberine as the principal colorant. Unambiguous identification of the dye components is essential if this, and thousands of related documents, are to be conserved. We have developed a technique that allows the detection of adsorbed molecules on tiny fragments of ancient dyed papers using liquid secondary ion mass spectrometry (L-SIMS) or fast atom bombardment mass spectrometry (FAB-MS). The surface of the paper is analyzed directly, which permits in situ dye analysis without the need for chemical extraction techniques.