11/22/16 -9:45 AM to 11:00 AM
Alexandra Velian, Ph.D.
"Inorganic Molecular Precursors: The Quest For Function Through Structure"
To develop new generation functional inorganic molecules and materials (e.g., catalysts or nanoscale electronics), the ability to control with atomic precision their structure is paramount. However, unlike in carbon chemistry, bonding in inorganic molecules and materials is significantly more difficult to encode, owing primarily to a relatively smaller synthetic toolbox. In this seminar I will describe two strategies to assemble inorganic molecules and materials under kinetic control, using different types of inorganic molecular precursors.
In the first part of the seminar, described is the assembly under mild conditions of value-added inorganic molecules that are otherwise inaccessible, using reactive small molecules as building blocks. Key is a versatile new approach to generate phosphorus reactive intermediates [e.g. diphosphorus (P2), phosphinidenes (RP) and phosphoalkyne (HCP)] using anthracene-based molecular precursors. Synthetic and mechanistic insights on their formations are discussed, as well as aspects of their reaction chemistry. Special attention will be given to the inorganic “click” reaction between diphosphorus and inorganic azide ion to form P2N3(−) anion, a rare example of an aromatic all-inorganic anion free of any protecting groups.
How about building atomically precise functional nanomaterials? One particularly attractive strategy to control the properties, composition and morphology of nanomaterials is to directly assemble them from well-defined inorganic molecular clusters of desirable electronic and magnetic properties. Ideal building blocks should (1) maintain structural integrity upon assembly; (2) form ordered assemblies of deliberate dimensionalities; and (3) upon assembly show long-range cooperative properties. In the second part of the talk, aspects of this strategy are discussed in the context of assembling cobalt selenide clusters with Co6Se8 cores into molecular assemblies of deliberate geometries with different degrees of electronic coupling (wires, macrocycles) as well as extended solids.
Velian is a MRSEC post-doctoral fellow working on creating well-defined functional nanostructures by linking atomically precise metal chalcogenide clusters. She completed her doctoral studies under the guidance of Professor Cummins at MIT, where she developed the synthesis of precursors to reactive phosphorus fragments and studied their behavior using chemical, mechanistic and computational methods. As an undergraduate student at Caltech, she was introduced to synthetic inorganic chemistry while in the group of Professor Jonas Peters. Later, as the first member of the Agapie group, she developed the synthesis of low-valent mono- and bimetallic complexes supported by a rigid terphenyl diphosphine framework.