(366u) Quantum Chemical Characterization of Selectivity Control in Sustainable Transformations

Research Interests: Modeling chemical transformations, computational catalysis, renewable energy, sustainable chemistry, DFT, Molecular Dynamics, structure-activity relationships

Improving catalytic selectivity is a long-standing theme for chemical synthesis. The key to attaining the desired chemo-, site- and/or stereoselectivity lies in the use of the appropriate catalyst or ligand. In this context, designing and developing new catalyst platforms for selective reactions can lead to selective access to one of two isomers or one of several possible products that the reaction can produce. To showcase the concepts of the strategies for selective reactions, I focus on different reactions taking advantage of the structural and electronic modularity of molecular complexes involved in sustainable transformations. Redox-controlled polymerization of cyclic esters catalyzed by iron-alkoxide complexes is an emerging area of switchable catalysis that can be used in polymer synthesis and macromolecular engineering. As catalysts, iron-based complexes are appealing as iron is earth-abundant and exhibits versatile chemical reactivity. However, the few iron catalysts reported for lactone polymerizations thus far have exhibited low activities and/or yielded broad molecular weight distributions. Nevertheless, iron-based systems remain of special interest because they offer unique opportunities for tuning of the catalyst spin state, overall charge, and oxidation state either of the metal or the ligand over a broad range of accessible redox potentials. Thus, I focus on quantum mechanical investigation of redox-controlled polymerization of cyclic esters catalyzed by bis(imino)pyridine iron-alkoxide complexes.

In the realm of rich redox chemistry of iron element, iron-sulfur clusters play crucial roles in biological electron transfer and enzymatic processes, such as nitrogen fixation and reversible H₂ oxidation/production, and CO₂ reduction. An atomistic understanding of short- and long-range regulation of redox properties of iron-sulfur proteins will enable the design of biological processes that underpin innovations for bioenergy and bioproduct production. To this end, I employ a multiscale modeling to quantify the role of coordination and solvent environment on redox properties of iron-sulfur clusters combining long timescale molecular dynamics (MD) simulations with hybrid quantum mechanics and molecular mechanics (QMMM) calculations. Along these lines, I also focus on the selective electroreduction of CO₂ to CO by porphyrin and phthalocyanine complexes of iron and cobalt metals. The rational functionalization of metal-porphyrins made it possible to reduce CO₂ to the prescribed composition of CO-H₂ mixture in water, but the activity can be very low. Thus, anchoring functionalized Fe and Co porphyrin and phthalocyanine molecular catalysts on support with high surface area is promising in the field of electrochemical CO₂ conversion. To this end, I present deeper mechanistic studies that can availably accelerate the rational design of the selective and stable metal-porphyrin and metal-phthalocyanine electrocatalysts with specific focus on Fe and Co metals.

In the context of steric control, I also present an enantioselective photocatalytic reaction where steric factors govern the product selectivity with a summary for the recipe of selection of geometric and electronic descriptors for accurate enantioselectivity prediction in asymmetric catalysis.