|M.Sc Student||Teplitzky Peter|
|Subject||Prediction of the Chemical and Physical Properties|
of Corroles via DFT Computations
|Department||Department of Chemistry||Supervisor||Professor Zeev Gross|
|Full Thesis text|
Corroles, the tri-anionic and one-carbon-short analog of porphyrins (heme), are of great interest, as they can chelate a wide range of transition metals and post-transition elements. Metallocorroles have been reported as catalysts for many reactions, with the insertion reaction of carbenes to a X-H bonds getting particularly large attention. Carbenes are known for being some of the most reactive species in organic chemistry, hence much focus has been placed on investigating catalysts involved in utilizing carbene precursors for organic chemistry. Within this category, porphyrin metal complexes have been investigated substantially more than their corrole counterparts. Most such reports conclude that when ethyl diazoacetate (EDA) is used as the carbene precursor the reaction proceeds through a metal-carbene complex as the key reaction intermediate.
Our group previously reported the iron(III) complex of tris(penta-fluorophenyl) corrole [FeIII(tpfc)] as highly efficient and selective catalysts for the insertion of EDA into N-H, S-H and even Si-H bonds. The experimental study done by our group suggested that when an iron(III) corrole is used as the reaction catalyst, a metal-carbene reaction intermediate is not likely. In order to investigate this claim and to identify alternative pathways, it was decided to use density functional theory (DFT) to analyze the reaction steps starting from the non interacting reagents up to the final products.
In this work DFT is used to investigate the mechanism of the carbenoid insertion reaction involving an iron(III) corrole and EDA, understanding electronic properties, intermediates, transition states and reaction thermodynamics. The commonly believed metal carbene intermediate is seriously called into question for the case of the iron(III) corrole. Orbital and energy analysis suggests that an N-bound EDA-iron(III) corrole intermediate plays a key role in the N-H reaction path following its formation. This study provides computational data to catalytic insertion reactions of the iron(III) corrole, adding to the limited computational studies on catalysis by metal corroles.
Another subject addressed in this work is the effects of the addition of CF3 groups to the β -pyrrole positions on the structural and electric properties of phosphorus corroles. A linear relation was found when examining orbital energies: both the HOMO and the LUMO were lowered with an increasing number of CF3 groups, with a stronger effect on the LUMO. This directly affects the HOMO-LUMO gap: it was also linearly affected and lowered with increasing number of CF3 moieties. This investigation will help to identify synthetic targets for new metallo corroles useful for catalytic reactions that involve redox process.