Renewing the Warwick 600 MHz Solid-State NMR System: Enabling State of the Art Technique Development and Novel Structural Applications

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When scientists investigate problems, like all good detectives they need clues as to what is happening. For a whole range of key problems, techniques that can reveal the local environment around an atom are crucial to provide insight into the structure at this level, which often governs how a material or molecule behaves. Nuclear Magnetic Resonance (NMR) spectroscopy has increased in importance throughout the sciences as it is an element specific probe that can distinguish very small changes in the surroundings of different sites (e.g. the number of corners by which an SiO4 unit is connected in a structure, or the different bonding of carbon, such as the differences between CH3 and CH2). NMR exploits the inherent magnetism of atomic nuclei: like the alignment of a compass needle in the Earth's magnetic field, nuclear magnets have a preferred direction when placed in a strong magnetic field. This preference, however, is weak and a nuclear magnet can be made to change its direction from e.g. aligned with to aligned against the magnetic field, by applying a resonant radio wave, i.e., one whose frequency and hence energy matches precisely the energy required to flip the nuclear magnet. The electrons surrounding the atomic nucleus are also affected by the presence of a magnetic field. Importantly, the resonant frequency of a particular nucleus depends very sensitively on this additional response of the electrons, such that the atomic nuclei act as spies of the local electron environment and hence the specific chemical bonding allowing it to be used to probe environments as described above.The resonant frequencies of different nuclear isotopes are well separated such that an NMR spectrum is specific to a particular chosen isotope. (An element can exist as different isotopes whereby there is the same number of protons but a different number of neutrons in the nucleus - the number refers to the total number of protons and neutrons.) This project will make use of much of the Periodic Table. Some nuclei are easy (such as 13C and 29Si) but others have been rarely observed by NMR (e.g. 33S, 47,49Ti). The project is to provide the state of the art equipment to allow the latest, modern experiments to be implemented and new ones designed. The equipment will be used in conjunction with a high magnetic field, and this makes possible some experiments that are not possible at lower fields because of the increased resolution for some nuclei and larger signal that the system will provide. One of the key plus points for NMR is that nuclei experience interactions that convey precise information about their surroundings. As an example the dipole interaction arises as the nuclear magnets are not isolated, but rather they interact in an analogous way to how two bar magnets either attract or repel when brought close together. Importantly, the magnitude of this so-called dipolar interaction is inversely proportional to the cubed distance between the two nuclear spins. Thus, the measurement of such dipolar interactions between a pair of say 17O and 1H nuclei directly gives the distance between an oxygen and a hydrogen atom. Such a distance can be used to quantify the degree of hydrogen bonding - an interaction that plays a key role in determining, e.g., the three-dimensional structure of a protein.A test of a good technique is that it is applicable to a wide range of problems. The equipment and the techniques developed as part of this project will be applied to both physical and life sciences. Problems to which the atomic scale structural information will be applied include: pharmaceuticals, catalysts for hydrocarbon conversion, volcanic materials, radioactive waste-storage glasses, new tissue replacement materials, understanding diseases and enzyme pathways and new electronic materials. It is through the partnership between problem-based and technique-based scientists that real progress is made.