Pragya
PMRF RESEARCH SCHOLAR
DEPARTMENT OF CHEMISTRY
IIT KANPUR
Research Interests
Bio-inorganic Chemistry
& Spectroscopic characterization
Active sites of various metalloenzymes contain high valent Metal-oxo's moieties that catalyze several crucial chemical transformations. Taking such designs as our model, we aim to generate mimic to such active sites using simple non-heme ligand designs. Our work is supported via the complete spectroscopic characterization of these high valent Metal-oxo species. Along with that, we do test the generated models for substrate oxidation qualitatively.
My Projects
​
PMRF Project
January 2021 - Present
Development of structural and functional models to the Oxygen Evolving Complex in Photosystem-II
​
Abstract :
​
With the rise in global energy demands and the consequences of extreme dependence on classical energy resources, there is an urgent need to look for greener and renewable resources. Photosystem-II (PS-II), which possesses Mn4CaO5 cluster in the active site, has an exceptional water splitting efficiency. Here, we propose the synthesis and spectroscopic characterization of MnIV/V(O)(µ-O)(LA) species (LA = Lewis acid) as the closest structural, if possible functional models to the active site of the oxygen-evolving complex in PS-II. We aim to understand the working reaction mechanism by characterizing the putative intermediates responsible for their excellent reactivity towards water oxidation, electron transfer, and oxygen atom transfer reactions. We believe that our results may help develop ideal, highly efficient artificial PS-II mimics capable of performing synthetically useful transformations.
Jan 2022 - Dec 2022
Abstract- The reaction of [(L)MnII]2+ (L = neutral polypyridine ligand framework) in the presence of mCPBA (mCPBA = m-Chloroperoxybenzoic acid) generates a putative MnV=O species at RT. The proposed MnV=O species is capable of performing the aromatic hydroxylation of Cl-benzoic acid derived from mCPBA to give [(L)MnIII(m-Cl-salicylate)]+, which in the presence of excess mCPBA generates a metastable [(L)MnV(O)(m-Cl-salicylate)]+, characterized by UV/Vis absorption, EPR, resonance Raman spectroscopy, and ESI-MS studies. The current study highlights the fact that [(L)MnIII(m-Cl-salicylate)]+ formation may not be a dead end for catalysis. Further, a plausible mechanism has been proposed for the formation of [(L)MnV(O)-m-Cl-salicylate)]+ from [(L)MnIII(m-Cl-salicylate)]+. The characterized transient [(L)MnV(O)-m-Cl-salicylate)]+ reported in the current work exhibits high reactivity for oxygen atom transfer reactions, supported by the electrophilic character depicted from Hammett studies using a series of para-substituted thioanisoles. The unprecedented study starting from a non-heme neutral polypyridine ligand framework paves a path for mimicking the natural active site of photosystem II under ambient conditions. Finally, evaluating the intracellular effect of Mn(II) complexes revealed an enhanced intracellular ROS and mitochondrial dysfunction to prevent the proliferation of hepatocellular carcinoma and breast cancer cells.
Formation of a Reactive [Mn(III)−O−Ce(IV)] Species and its Facile Equilibrium with Related Mn(IV)(OX) (X = Sc or H) Complexes
Jan 2022- Dec 2024
Lewis acid-bound high valent Mn-oxo species are of great importance due to their relevance to photosystem II. Here, we report the synthesis of a unique [(BnTPEN)Mn(III)−O−Ce(IV)(NO3)4]+ adduct (2) by the reaction of (BnTPEN)Mn(II) (1) with 4 eq. ceric ammonium nitrate. 2 has been characterized using UV/Vis, NMR, resonance Raman spectroscopy, as well as by mass spectrometry. Treatment of 2 with Sc(III)(OTf)3 results in the formation of (BnTPEN)Mn(IV)−O−Sc(III) (3), while HClO4 addition to 2 forms (BnTPEN)Mn(IV)−OH (4), reverting to 2 upon Ce(III)(NO3)3 addition. 2 can also be prepared by the oxidation of 1 eq. Ce(III)(NO3)3 with [(BnTPEN)Mn(IV)=O]2+ (5). In addition, the EPR spectroscopy revealed the elegant temperature-dependent equilibria between 2 and Mn(IV) species. The binding of redox-active Ce(IV) boosts electron transfer efficiency of 2 towards ferrocenes. Remarkably, the newly characterized Mn(III)−O−Ce(IV) species can carry out O-atom and H-atom transfer reactions.
Pivotal m-X-salicylates deciphering the fate of high valent Mn(V)=O
Jan 2023 - Dec 2024
An alternative and efficient route has been derived to generate the high valent [Mn(V)=O(m-Cl-salicylate)]+ intermediates with a series of non-heme neutral ligand frameworks at 20 °C. The current method provides an advantage with feasibility in maintaining stoichiometric oxidant ratios along with the crucial variations of the salicylate moieties in tuning the reactivity of Mn(V)=O species. An in-depth analysis of the Hammett studies revealed that the bound 5-X-salicylate (X=Cl, and NO2) drastically alters the corresponding Mn(V)=O's reactivity rates. In contrast, variations in the parent ligand frameworks resulted in consistent ρ values with increased lifetimes depicting the ligand's role in stabilization. Lastly, the complexes have been characterized to promote oxidative stress and prevent the proliferation of cancer cells effectively.
A closest structural mimic to PS-II using non-heme tetradentate ligand design
Jan 2023 - Dec 2024
This work is under progress and will soon be communicated.
Collaborative publications:
Visible light-mediated synthesis of quinazolinones and benzothiadiazine-1,1-dioxides utilizing aliphatic alcohols
S Kumari, S Roy, P Arora, S Kundu
Organic & Biomolecular Chemistry 22 (20), 4172-4178
A Schiff base functioning as a highly selective colorimetric sensor for Cu2+ ion
GGV Kumar, P Arora, A Draksharapu
Materials Letters, 136875​
Electronic Feature Modification of Ni and Co Free Metal–Organic Framework Nanoparticles by Vanadium Introduction for Water Oxidation
B Singh, N Verma, P Arora, A Draksharapu
ACS Applied Nano Materials
"Believe you can and you're halfway there"
Theodore Roosevelt
