Theses

Permanent URI for this community

https://ir.iitj.ac.in/handle/123456789/4

Browse

Browsing Theses by Supervisor "Chakraborty, Subrata"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Publication
    Development Of Chromium and Molybdenum Complexes for CO₂ Hydrogenation and Biological Application
    (Indian Institute of Technology, Jodhpur, 2024-12-31) Chakraborty, Subrata
    The catalytic hydrogenation of the potent greenhouse gas carbon dioxide to value-added products represents a sought-after methodology in academia and industry. Molecular complexes facilitate the conversion of CO2 into formic acid, which is a beneficial process because formic acid is a versatile feedstock in many industries and can be used as a potential renewable hydrogen storage material. Group VI elements chromium and molybdenum are earth-abundant and low-toxic metals, and their chemistry towards the utilization of CO2 has been sparsely investigated. Therefore, we examined both the direct and indirect hydrogenation of CO2 using low-valent Mo(0) and Cr(0) complexes supported by multidentate phosphine ligands with varied bite angles. We achieved maximum formate TONs of 950 and 2,59000, the highest for any Mo and Cr system reported in the literature thus far. Mechanistic probing revealed that the reaction proceeded via the formation of anionic hydride species in both cases. Based on the initial success with low-valent Cr species, we performed CO2 hydrogenation using high-valent Cr (II) pincer complexes and obtained formate with a TON of 87,00. We also carried out the transfer hydrogenation of CO2 using isopropanol as the hydrogen source under ambient conditions using bidentate DPPP ligand-based low-valent chromium complex. A formate TON of up to 1974 was recorded using 1 bar CO2. This is a state-of-the-art discovery with regard to base metal catalysts. Lastly, we developed a NIR II-emitting low-valent Schiff base-supported chromium complex that is effective as an antibacterial agent against gram-positive pathogenic bacteria selectively. The current study deals with transition metal complexes derived from non-noble earth-abundant metals for catalytic and biological applications, and we believe this research opens new avenues for developing next-generation innovative catalysts and bioactive compounds.
  • No Thumbnail Available
    Publication
    Earth Abundant Manganese Catalysed Sustainable Chemical Transformations
    (Indian Institute of Technology, Jodhpur, 2025) Chakraborty, Subrata
    The growing interest in Earth-abundant transition metals for organometallic catalysis stems from their economic advantages, availability, and unique catalytic properties. Manganese, the third most abundant transition metal in the Earth's crust, has emerged as a promising alternative to precious metals such as platinum, palladium, and rhodium, which are commonly used in catalytic processes like (de)hydrogenation, hydroboration, hydrosilylation. While precious metal catalysts are renowned for their high activity and robustness, their high cost and limited availability pose significant challenges. In contrast, manganese offers a more sustainable and cost-effective option, though it often requires more advanced catalyst design to match the performance of precious metal-based systems. Manganese catalysts are typically designed around three key principles: metal–ligand bifunctionality, ligand hemi-lability, and redox activity. By optimizing these factors, manganese catalysts can be engineered to achieve competitive turnover numbers, although they may not always match the efficiency of precious metals in certain applications. This thesis provides a comprehensive analysis of the catalytic properties of manganese complexes, comparing their activity, versatility, and efficiency in the direction of alkylation, (de)hydrogenation, deamination and hydration reactions. It also highlights the critical challenges in manganese catalyst design, particularly in ligand optimization, and offers insights into how these catalysts can be improved for broader catalytic applications.