Event organiserSchool of Chemistry

Professor Kim Baines from Western University, London, Ontario presents: ‘Fun with Low Valent Si and Ge Complexes: From Mechanism to Catalysis’.

One of the most important advances in inorganic chemistry over the last 30 years was the discovery of stable low valent species of the heavier main group elements. The detailed characterization of these unsaturated species has profoundly influenced our understanding of structure and bonding and the diverse reactivity of these compounds has provided facile entry into a number of previously unknown functional molecules.

Our investigations into the chemistry of ditetrelenes and low valent Group 14 cations are guided by our interest in the fundamental chemistry of ditetrelenes particularly pertaining to small molecule activations and potential applications of low valent compounds, particularly in catalysis. In this lecture, a detailed view of the activation of ammonia by a disilene and the hydrosilylation of carbonyl compounds by low valent germanium cations will be presented.

From Grinding to Ignition: Opportunities of Solid-State Chemistry in Green Chemistry and Materials Science

Tomislav Friśčić (Department of Chemistry, McGill University)

Abstract

This presentation will outline our group’s recent advances in using solid-state reactivity for the development of cleaner, safer synthetic methodologies and materials designs. In particular, it will provide an overview of the emergence of mechanochemistry, i.e. chemical transformations induced by mechanical agitation such as grinding, milling, or extrusion, as a uniquely general solventless synthetic methodology that can also provide access to novel reactivity and molecules.[1]

We will also show how focusing on the mechanistic aspects of mechanochemical reactions, and in particular the use of methodologies for real-time and in situ monitoring of milling processes,[2] can lead to advances in the fundamental understanding and prediction of structures and thermodynamic stabilities of advanced materials, such as metal-organic frameworks (MOFs).[3,4] Specifically, we will show how mechanistic investigations of mechanochemical reactions led to the discovery of simple guidelines to design MOFs with controllable stability, based on established or readily accessible descriptors of molecular stability.[5]

Finally, we will use our studies of MOF stability and energetics as a springboard to highlight a potential new application of this class of materials for developing a new type of greener and uniquely tuneable aerospace fuels based on solid-state designs.[6]

References
[1] Friśčić et al. Angew. Chem. Int. Ed. 2020, 59, 1018; [2] Friśčić et al. Nature Chem. 2013, 5, 66; [3] Akimbekov et al. J. Am. Chem. Soc. 2017, 139, 7952; [4] Arhangelskis et al. Chem. Mater. 2019, 31, 3777; [5] Novendra et al. J. Am. Chem. Soc. 2020, 142, 21720; [6] Titi et al. Sci. Adv. 2019, 5, eaav9044.

N-heterocyclic carbenes (NHCs) are strong ligands and a promising alternative to thiols for self-assembled monolayers. However controlling their adsorption on solid surfaces is a current challenge of surface functionalization. I will introduce our recent work, that focuses on understanding [Chem. Sci., 2017, 8, 8301] and controlling the assembly of NHCs on metal-vacuum interfaces. Our analysis encompasses an integration of microscopy, diffraction, spectroscopy and desorption in ultra-high vacuum combined with theoretical considerations to generate a high degree of precision in the understanding of interfacial processes at the atomic level. To control the NHC tethering we exploited the surface chemistry of a well-established building block for on-surface assembly: a porphyrin [J. Phys. Chem. C, 2021, 125, 3215; Angew. Chem. Int. Ed., 2021, 60, 16561]. A suitable metalloporphyrin is a pedestal that orients and defines the lateral arrangement of NHCs on a planar surface by providing a single atom site. We applied NHCs on a self-assembled metalloporphyrin layer and discovered that they are suitable pillars for the formation of out-of-plane architectures [J. Am. Chem. Soc., 2021, 143, 4433]. The resulting modular arrangement of NHCs allows us to address individual ligands by controlled manipulation with the tip of a scanning tunnelling microscope, creating patterned structures on the nanometer scale. Under certain conditions, we also observed a fascinating, dynamic interface rearrangement based on the NHC ligand acting as a molecular porter for metalloporphyrin molecules: they transfer porphyrin molecules from the first to the second molecular layer. Harnessing these dynamic events will serve the engineering of atomically precise NHC-containing complex interfaces.

Materials by design is the rational prediction and creation of functional materials with defined properties. Its goal is to meet current and future societal needs for better or more complex materials, from biocompatible materials in medicine to lightweight alloys for space applications and energy generation, storage, and transport. Unfortunately the chemistry underlying modern materials science and engineering has lagged other sub-fields in an extremely critical area: the ability to selectively make and break bonds in the solid state. This is due to limited synthetic methodology and method development. True materials by design cannot be achieved until reliable synthetic capabilities are developed that can actually produce the specified materials. In this talk, I will highlight the progress being made in such synthesis by design, with a particular focus on quantum materials – a class of material in which quantum phenomena not only underlie but are ‘writ large’ across macroscopic materials. What is a quantum material? How can chemistry be used to design and improve them? How can their unique properties be used to improve society? Examples will be drawn from topology and quantum magnetism.

Title to be confirmed

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This year’s Postgraduate Symposium will be held over 2 days on the 8-9th of December. More details to follow on abstract submission and how the event will take place.