• Dipanwita Das

      Articles written in Journal of Chemical Sciences

    • Electronic structures of ruthenium complexes encircling non-innocent ligand assembly

      Amit Das Dipanwita Das Tanaya Kundu Goutam Kumar Lahiri

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      Electronic structural forms of selected mononuclear and dinuclear ruthenium complexes encompassing redox non-innocent terminal as well as bridging ligands have been addressed. The sensitive valence and spin situations of the complexes have been established in the native and accessible redox states via detailed analysis of their crystal structures, electrochemistry, UV/VIS/NIR spectroelectrochemistry, EPR signatures at the paramagnetic states and DFT calculations. Mononuclear complexes exhibit significant variations in valence and spin distribution processes based on the simple modification of the non-innocent ligand frameworks as well as electronic nature of the co-ligands, 𝜎-donating or 𝜋-accepting. Dinuclear complexes with modified pyrazine, 𝑝-quinone and azo-derived redox-active bridging ligands show complex features including redoxinduced electron-transfer (RIET), remote metal to metal spin-interaction in a three-spin metal-bridge-metal arrangement as well as electron-transfer driven chemical transformation (EC).

    • Metal-Organic Framework and Carbon Black supported MOFs as dynamic electrocatalyst for oxygen reduction reaction in an alkaline electrolyte


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      The Pt-based expensive catalysts and sluggish kinetics at cathode in oxygen reduction reaction(ORR) hinder the rapid commercialization of fuel cells. The quest for cheap, non-noble metal catalysts toreplace Pt-based catalysts has thus become a critical issue in the field of fuel cells. The carbon black (CB) andCB supported catalyst have been explored with the ultimate goal of finding a substitute for Pt-based catalystsin fuel cells. In the present work, we synthesized Zn-based MOF (1), 1 selectivity gives H2O2 followed bytwo-electron pathways. However, sample 1 modification might be needed to enhance its selectivity for thegeneration of H2O. Two composites of MOFs with carbon black and 1 were prepared to increase the H2Oyield, called 1.CB and 1.SCB. The electrochemical generation of H2O2 was analyzed by the rotating ringdisk electrode (RRDE) using catalyst 1. Following the addition of CB, H2O2 yields decreased from above93% (1) to 59% and 75% for 1.CB and 1.SCB, respectively. CB modified catalysts moved towards fourelectronpathways due to the conductive nature of CB. Electrochemical Impedance Spectroscopy (EIS) hasalso been performed to study in detail the conductivity effect of CB and kinetic behavior of ORR in alkalineelectrolyte. This research opens up a new path for ORR to advance non-precious metal catalysts based on MOFs.

      Synopsis: This paper describes how we synthesized carbon Black (CB) supported MOF: Zn-based MOF (1), 1 selectivity gives H2O2 (two-electron pathways). Two composites of MOFs (1⊃CB and 1⊃SCB) were prepared to increase the H2O yield. After addition of CB, H2O2 yields decreased from above 93% (1) to 75% (1⊃SCB) and 59% (1⊃CB).

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