Our research concerns mimicking metalloproteins which play essential roles in such crucial biochemical processes as group transfer, hydrogen atom abstraction, electron transfer, etc. We aim to understand the relationship between the structures and catalytic mechanisms of such model complexes and to elucidate the biochemical mechanisms. Currently, the majority of our efforts are in defining structure-reactivity relationships among members of a large class of non-heme enzyme models to activate molecular oxygen or external oxidants for such diverse oxidation reactions. Our interest stems primarily from the recent discovery that members of this class while catalyzing quite distinct oxidation reactions, have very similar structures. We and our collaborators bring to bear a dazzling array of chemical manipulation and spectroscopic methods to learn how to rationally alter the structure of the class to have a mechanism and outcome mimicking that of another member.

OpenTox Virtual Conference 2021 

Mechanistic investigations of high-valent metal intermediates of biomimetic  non-heme model systems 

Metalloenzymes are known to play a pivotal role in catalyzing a plethora of biological and biochemical reactions. These transformations are directed by a variety of high-valent reactive intermediates that undergo crucial redox reactions by atom-transfer or electron-transfer or radical reaction pathways.  These high-valent reactive intermediates of non-heme model systems are known to be influenced by factors like coordination motifs and topology, ligand architecture, pH, spin states of metal ions,  solvation, and temperature.1 The factors that govern the reactivity profiles are often associated with the mechanistic pathways followed. Hence, it is important to dig deep into the mechanistic details of the reactions performed by these model systems.  

Non-heme iron-oxo intermediates have been identified as potential reactive intermediates in a variety of electrophilic reactions. It can catalyze C-H activation reactions and can also undergo heteroatom oxidation. Subtle modifications in a ligand skeleton can be seen to hugely accelerate reaction rates catalysed by non-heme iron-oxo complexes.2 Also, with the help of a series of structurally tweaked ligand frameworks, the governing factors that orchestrate the eccentric reactivity trends of iron-oxo  moieties have been brought to the forefront.3 With the help of a couple of isomeric bispidine Mn(III)- 

peroxo complexes, a new mechanism for aldehyde deformylation reaction has been established. Keto enol tautomerism in the reaction mechanism can be seen to trigger an electrophilic pathway instead of  the commonly portrayed nucleophilic mechanism.4 

References: 

1. Mukherjee, G.; Sastri, C. V. Isr. J. Chem. 2020, 60, 1032-1048. 
2. Mukherjee, G.; Lee, C. W. Z.; Nag, S. S.; Alili, A.; Cantú Reinhard, F. G.; Kumar, D.; Sastri, C. V.; de  Visser, S. P. Dalton. Trans. 2018, 47, 14945-14957. 
3. Mukherjee, G.; Alili, A.; Barman, P.; Kumar, D.; Sastri, C. V.; de Visser, S. P., Chem. Eur. J. 2019, 25,  5086-5098.