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Chemistry at Dalhousie University.

Dalhousie University, the host institution of the 73rd Canadian Chemical Conference and the 40th Canadian Chemical Engineering Conference, in July 1990, has been a centre for teaching and research in chemistry in the Maritimes for over 100 years. The associated graduate programme dates from 1871, the year that the first MA degree was awarded. The first PhD degree was awarded in 1964, and in the last 25 years the department has experienced a rapid expansion of research personnel, resources and equipment, and it is now one of the major chemistry departments in Canada. Many graduates have gone on to enjoy distinguished careers in chemistry and other disciplines. Funding from federal government grants and Dalhousie University support research in all areas of modern chemistry. In addition, three research centres, headed by chemistry department members, have been established: the Trace Analysis Research Centre (1971), the SLOWPOKE Nuclear Reactor (1976) and the Atlantic Region Nuclear Magnetic Resonance Centre (1981).

The department consists of 26 faculty members, eight instructors, 40 graduate students, 30 postdoctoral fellows and visiting scientists, and 14 support staff. Over half of the graduate students hold national or international scholarships, including NSERC and Izaak Walton Killam Memorial Scholarships. The department also offers the highly prestigious Walter J. Chute Graduate Scholarship, presently valued at $26,966. Walter J. Chute, FCIC, Professor Emeritus, remains an active member of the department, having come to Dalhousie 47 years ago.

Support operations include an electronics shop, a glassblowing shop with a master glassblower and a machine shop. The Killam Library holds over 150,000 bound scientific volumes, and subscribes to more than 2,000 scientific periodicals. Major scientific facilities in the Halifax area include the Atlantic Research Laboratory of the National Research Council of Canada (located on the Dalhousie campus) (see May '90, p.16), the Bedford Institute of Oceanography (a leading marine research establishment), the Canadian Institute of Fisheries Research and Technology, Department of Fisheries and Oceans Physical and Chemical Sciences, the Nova Scotia Research Foundation Corporation (see May'90, p.13) and the Technical University of Nova Scotia.

A five-year, $9,800,000 project to extend and renovate the department began in the summer of 1986. Phase I is complete giving Dalhousie one of the best undergraduate laboratory complexes in Canada. The current chemistry building is being modernized, to accommodate the needs of present day and future research. Dalhousie is planning a 25% increase in graduate student enrolment during the next five years, and the Department of Chemistry is looking forward to this challenge.

The department has an active weekly seminar programme, which allows interaction with leading chemists from all over the world. In addition, each year an outstanding scientist visits the department for several days and presents the Walter J. Chute Distinguished Lecture Series. R.U. Lemieux, FCIC, of the University of Alberta inaugurated the series in 1980 and the following years have featured the following distinguished scientists: Leo Yaffe, FCIC (McGill), W.N. Lipscomb (Harvard), J.C. Polanyi, FCIC (Toronto), R.J.P. Williams (Oxford), R. Breslow (Columbia), D. Hodgkin (Oxford), R.N. Zare (Stanford), M.S. Wrighton (MIT) and A. Pines (Berkeley).

Computer Assisted Learning

A local area computer network, consisting of 27 PC-clone workstations, has recently been installed. Tom Forrest, Charles Warren and other department members have developed a range of Computer Assisted Learning exercises, heavily used by all students.

Expert systems for spectral interpretation are being developed by Forrest. The AI language, Prolog, is being exploited in the development of these systems. One such system, EXP' AIR, an infrared interpretation assistant, has been developed in collaboration with the University of Nice. It is currently being used in various laboratories.

Trace Analysis Research Centre

In 1971, the NRC awarded a Negotiated Development Grant to Dalhousie University to establish a centre of excellence in analytical chemistry. The result was the Trace Analysis Research Centre (TARC) which has strengthened analytical chemistry in Canada. TARC has initiated projects that apply analytical techniques to solving particular problems of developing countries. Two of its members have won the Fisher Scientific Award, presented annually by the Canadian Society for Chemistry to an outstanding Canadian analytical chemist.

The faculty are Walter Aue, FCIC; Amares Chatt, FCIC; Robert Guy; Louis Ramaley, FCIC; Douglas Ryan, FCIC (Emeritus); Roger Stephens; and Peter Wentzell, MCIC. Their interests and research projects include atomic spectroscopy, magneto-optic effects, optical polarimetry, instrumentation flow analysis systems, computer automation), chemometrics, acoustic emission analysis, speciation metal ions, organic pollutants), gas chromatography (support-bonded polymers, selective detectors, confirmation reactions), electro-chemistry, mass spectrometry (including coupling to various separation techniques, nuclear analytical chemistry (conventional, epithermal and cyclic neutron activation analysis), nuclear waste management, metallobiochemistry (bioavailability, nutritional studies, disease correlation with trace elements), and preconcentration methods.

Extensive instrumental facilities are available in all the above areas, an excellent example of such a facility being the Dalhousie Nuclear Research Reactor (SLOWPOKE). This small reactor is designed specifically for neutron activation analysis. The core runs at a temperature low enough so that all types of samples, including sensitive biological samples, can be activated for analysis.

Atlantic Region Magnetic Resonance Centre

The centre was formed in 1981. Its instrumentation includes a Nicolet NT-360 superconducting NMR spectrometer and a high-power, wide-bore Bruker MSL-200 NMR spectrometer equipped with probes for magic-angle spinning and cross-polarisation experiments on solids, single crystal NMR studies and high-resolution NMR studies.

Centre manager Don Hooper, MCIC, is interested in the application of high field NMR spectroscopic methods towards the solution of problems in the structure and dynamics of organic and inorganic compounds and clinical applications. Department faculty use the centre heavily. In particular, Rod Wasylishen, FCIC, uses modern multinuclear NMR techniques to investigate molecular structure and dynamics in liquids and in the solid state. His group has initiated a comprehensive study of nitrogen and phosphorus chemical shielding tensors in compounds in which these atoms are involved in unique chemical bonding arrangements. In addition, efg tensors at quadrupolar nuclei and J tensors involving adjacent spin nuclei also are being explored. Solution studies involve rotational dynamics, isotope effects on NMR parameters, etc. The centre also is extensively used by the synthetic chemists for characterisation and by Jan Kwak, FCIC, and Wasylishen for the study of micellar and polymer solutions, as well as a variety of other colloidal systems.

The Chemistry of Condensed Materials

One Dalhousie strength is condensed matter chemistry including the physical and chemical properties of solids and solutions. Various modern instrumental facilities are available for condensed matter investigations, including an Enraf-Nonius CAD-4 X-ray diffractometer, two high field NMR instruments (mentioned above) and various solution and solid state, high accuracy calorimeters, thermal conductivity apparatus.

Stanley Cameron's, MCIC, research is in single crystal X-ray diffraction. Current interests include low-temperature residual electron density studies to examine bonding electrons and non-bonding electron pairs; crystal packing with an emphasis on the factors that influence the selection of the particular packing arrangements in a sequence of related compounds; packing dynamics in a crystal and its variation with changing temperature; hydrogen bonding studies and X-ray crystal structure determinations that look intriguing, interesting, odd, or that are needed by colleagues.

Osvald Knop, FCIC, investigates structural inorganic chemistry in its various aspects. In common with Cameron, Wasylishen and Mary Anne White, MCIC, he has an interest in orientational disorder in solids.

Kwak's research is in the area of colloid and polymer chemistry. Studies focus on mixed micellar systems, polymer solutions, vesicles and liposomes, and a variety of applications from ceramic processing to drug delivery systems.

Using computer simulation and other theoretical techniques, Peter Kusalik, MCIC, studies simple models for polar solvents and electrolyte solutions. Both the equilibrium and dynamic properties of these systems are of interest.

Oxygen sensors, based on zirconia solid electrolytes, are being developed (and patented) by Phil Pacey, MCIC, and his research group.

Wasylishen uses NMR spectroscopy to investigate a variety of interactions in the solid state and in solution. Other current work in his group includes conformational studies in solid and solution, chemical shielding tensors, dipolar coupling, indirect spin-spin and quadrupolar interactions in the solid state, and single crystal NMR studies.

White's research is in the area of thermal properties of solids, especially solids that exhibit translational, orientational or magnetic disorder. One current topic is the relationship between structure and heat transfer in condensed matter. Another is the characterization of phase transitions in solids, through calorimetric techniques developed by White and her research group. While the work aims at understanding weak forces in solids, some investigations have led to interesting applications, such as the discovery of a novel family of heat storage materials.

Kinetics and Reaction Mechanisms

There are three separate research groups directing their attention towards kinetics and reaction mechanisms.

Ken Leffek, FCIC (Chairman of the CSC/CSChE Conference), employs spectrophotometric techniques, such as stopped-flow spectrophotometry, to study primary deuterium isotope effects on proton-transfer reactions from organic carbon acids, primary isotope effects on elimination reactions, and nucleophilic addition and substitution reactions of olefins.

A more physical approach is taken by Pacey in his study of the rates of chemical reactions at low and high temperatures to provide information about the energies of reacting species. Picogram gas chromatography and electron spin resonance spectroscopy are used with fast flow systems in which the concentrations of intermediates have not reached their steady-state values. Absolute rate constants are determined for elementary gas and solid phase processes and for reactions at the gas-solid interface. Several processes exhibit curved Arrhenius plots.

Reaction mechanism studies for both ground and excited-state organic reactions are the principal interest in Jim Pincock's, MCIC, laboratory, equipped to carry out 'state-of-the-art' experiments for measuring rate constants of photochemical reactions. The problem of quenching by protons that result from the enhanced basicity of excited states is also under investigation, and an acidity scale has been developed to analyze the rate constants of these reactions. Methods of photocatalysis are being examined.

Photochemistry

The chemistry of excited state systems is used by a number of department researchers, toward the development of quantum chemistry, organic synthesis, and reaction mechanisms.

Visible emission spectroscopy and high-resolution laser spectroscopy are used by John Coxon, MCIC, for detailed studies on the quantum states (rotational, vibrational and electronic) of small molecules (especially diatomic free radicals and ions) in the gas phase. The laboratory has excellent resources, including scanning grating spectrometers, computational facilities and a 'state-of-the-art', automated single-frequency ring dye laser. In addition to analyses of line spectra of novel free radicals and molecular ions from electrical discharges (Al[O.sub.2], [O.sub.2]+, BO, TiN), interests include the development of procedures that identify deviations from the Born-Oppenheimer approximation of separation of states.

Understanding of reaction mechanisms and the development of organic synthetic methods based on photochemical excitation are major areas of interest for Don Arnold, FCIC, and Pincock. In addition to standard instrumentation, the organic chemists have a PRA single-photon counter for measuring excited, singlet-state lifetimes, a Perkin-Elmer MPF-66 fluorescence spectrometer and a quantum yield bench.

Pincock has begun to obtain a real understanding of the factors that control the competition between homolytic and heterolytic photocleavage of benzylic substrates and is trying to apply these principles to develop synthetically useful procedures. Recently, rate constants for electron transfer in radical pairs have been determined and shown to fit the Marcus 'inverted' region.

Arnold is exploiting the high reactivity of radical cations and anions, formed by photochemical electron transfer, towards useful synthetic processes.

Physical Organic Chemistry

Kinetics and reaction mechanisms of organic systems are examined by Leffek using spectrophotometric techniques. Ground state and excited state organic reaction rates and mechanisms are studied by Pincock's group.

In Arnold's laboratory l,n-radical ions are generated electrochemically and used as intermediates towards products which are difficult to prepare by the more traditional techniques. In addition, the group is attempting to evaluate the importance of substituent effects on the reactivity and stability of free radicals, diradicals and triplets. The research is made possible with use of a Varian E-109B ESR spectrometer and an H.-P. 5890 GCMS, along with the more standard synthetic and spectroscopic instrumentation.

Theoretical aspects of physical organic chemistry are approached from two view points. Conformational analysis by means of molecular mechanics calculations is a continuing interest of Bruce Grindley, MCIC, while Russ Boyd, FCIC, carries out fundamental studies using contemporary ab initio methods. Both studies are carried out in conjunction with experimental collaboration.

Synthetic Chemistry

The Department of Chemistry supports synthetic chemistry in terms of spectroscopic instrumentation, X-ray crystallography and extensive specialised 'state-of-the-art' synthetic equipment within specific laboratories.

The synthesis and comprehensive study of compounds containing new bonding arrangements for the heavier non-metal elements are the principal goals of Neil Burford, MCIC. Sophisticated synthetic procedures have been developed to handle highly reactive species. Standard physical and spectroscopic techniques such as IR, UV-visible, mass spectrometry and multinuclear NMR are used for characterization, together with X-ray crystallography. Attempts are made to rationalize the structure and chemistry of these compounds on the basis of a well-developed understanding of their electronic structure.

Howard Clark, FCIC, and Kevin Grundy study coordination chemistry, with specific interests in structure and reactivity, respectively. Clark's research aims to develop an understanding of how sterically demanding ligands are accommodated about a metal centre. Numerous crystal structure determinations and solid-state NMR studies of a variety of bulky phosphine complexes of platinum(II) indicate the ease with which steric distortion occurs in overcrowded complexes. Evidence for C-H bond activation in some of these complexes has led to current investigation about the role of steric factors in such bond cleavages. Grundy is interested in the chemistry of small reactive molecules rendered kinetically stable via coordination to transition metal complexes. Frequently, these unusual ligands have to be assembled within the coordination sphere of the metal. Of particular interest are ligands capable of exhibiting amphoteric or non-innocent behaviour and how this is affected by changes in the electronic structure and ligand environment of the metal. The current emphasis is on 1 and 2 bond complexes of simple molecules using nitrogen, phosphorus, oxygen and sulphur as donor atoms.

Stereochemistry is among the interests of both Grindley and Stuart Grossert, FCIC. Under the general heading of 'carbohydrate chemistry', Grindley's research covers a number of areas, such as conformational analysis and the development of methods for stereospecific synthesis. The development of methods for the synthesis of biologically active compounds, usually related to carbohydrates, includes new approaches to the synthesis of 3-deoxy-D-manono-octulosonic acid analogues, and to C-glycosyl derivatives. Present attention is addressed to understanding the causes of the outstanding regioselectivity obtained in reactions of dibutylstannylene acetals. Methods employed to solve these problems include Sn-119 NMR spectroscopy and molecular mechanics calculations, as well as analysis of reaction products.

Grossert's aim is the synthesis of molecules with novel, complex, sulphur-containing functional groups. Recent work has centered on studying the stereoselectivity of reactions of certain [beta]-ketosulfones, in which the proximity of a sterically hindered sulfonyl group to other functional groups leads to diastereoselectivity in the reaction of nucleophiles with the carbonyl group. Current work includes extensions of this concept and the preparation of carbon acids that have potential as novel surfactants. Approaches to synthesis include the application of high pressures to the liquid state, an area of increasing interest among chemists. Work on all molecules includes studying novel structural features by X-ray crystallography (in collaboration with Cameron), together with their chemical and spectroscopic (primarily NMR and mass spectral) properties.

Theoretical Chemistry

Research here is benefiting from the recent acquisition of a dedicated graphics mini-supercomputer. This machine, an FPS M350SX with 96 Mbytes of main memory and 1.5 Gbytes of disk storage, delivers near supercomputer performance. Moreover, its high-resolution, high-performance graphics capabilities are extremely useful for the visualisation of data. Quantum chemistry, molecular mechanics and molecular dynamics simulations are among the applications which are taking advantage of this powerful research tool.

The research activities of Boyd's group are focussed on fundamental and applied topics in quantum chemistry. Much work is motivated by the need to develop of efficient computational methods for the inclusion of electron correlation. Current interests include the evaluation of pair distribution functions in the excited states of atoms and in molecular systems. This research complements the group's investigations of the topological properties of the electron density distributions of molecules and the relationships between the topological properties and chemical concepts, such as bond order, electronegativity, hydrogen bonding and transition states.

The more applied projects of Boyd's group use ab initio molecular orbital theory to study novel chemical problems. These studies are frequently carried out in collaboration with experimentalists and yield information which usually is unobtainable by other methods. Such applications often lead to suggestions for new experiments and for refinements of the models upon which the theories are based.

Working in the area of liquid state theory and statistical mechanics, the research group of Kusalik has the study of polar solvents and electrolyte solutions as its central focus. This research should improve our understanding of the relationships between the microscopic and macroscopic behaviour of simple model systems, thereby providing insights into many poorly understood aspects of real liquids. Extensive molecular dynamics simulations are used to probe solvation behaviour and dielectric response. Analytic and quasi-analytic theories represent a complementary approach for investigating the structural, thermodynamic and dielectric properties of these systems.

Semi-empirical methods are being used by Pacey to investigate the forces between atoms in stable molecules and during bond rupture. The work is directed toward the theoretical basis of understanding quantum mechanical tunnelling and hindered internal rotations.

Techniques in molecular graphics are being applied to the study of the topology of the electron density distributions in small molecules by Warren. By examining the 3-D surface of the charge density and its associated derivatives, one can gain a better understanding of chemical bonding.

The chemistry department welcomes all participants in the 1990 CSC/CSChE Conference to the Dalhousie Campus. We invite our colleagues to visit our research laboratories and to try our computer-assisted learning facilities located in the Chemistry Resource Centre. We hope to see many of our friends at the Dal-Chem Open House to be held Monday, July 16 through Thursday, July 19, 1990, from 1700 to 1800 also in the Chemistry Resource Centre, Room 167, in the Chemistry Building.
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Author:Burford, Neil
Publication:Canadian Chemical News
Date:Jun 1, 1990
Words:3030
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