The Schiff base (SB) containing metal complexes are versatile in nature showing captivating properties in different areas of chemistry. As a consequence, they continue to attract the attention of chemists. These are air-stable complexes containing different metal ions that possess engrossing magnetic and electrochemical properties.1 The latter is less explored. In the first chapter, the synthesis of SB chelated Mn complexes and their magnetic properties associated with structural topology would be discussed. In addition, the synthesis and characterization of Mn-Ni heteronuclear and homonuclear Cobalt-complexes containing ON-donor ligands would be also explained. In the remaining three chapters, the synthesis and future scope of SB containing different metal complexes are studied. In the second working chapter, SB containing Ni4 cluster was synthesized, which reduces N2 to NH3 electrochemically in a non-aqueous medium. The compound contains O, N donors (hard) which structurally differ from the existing metal electrocatalysts as they usually have sulfide donors (soft) to mimic the activity of the nitrogenase enzyme. The active catalyst and intermediates have been characterized using ESI-MS, EPR studies, and DFT calculations. The compound is electrochemically studied thoroughly and the onset potential is at -2.3 V vs Fc+/Fc. The obtained faradaic efficiency and NH3 formation rate are 26.5% and 36 mg h-1cm-2 respectively. In the next chapter, four new SB coordinated Fe(III) containing complexes/clusters were synthesized and two of them are found to act as heterogeneous catalysts for electrochemical nitrogen reduction reaction (eNRR; N2 + 6 H+ + 6 e− → 2 NH3) from the preliminary analysis. The compounds are structurally characterized by SC-XRD, HR-MS, and EPR studies. However, a significant part of extensive electrochemical analysis needs to be addressed in the future. In the last chapter, the synthesis of Ni(II)2 and Ni13 molecular clusters would be discussed. Along with that, from the initial studies, we noticed that the 3d-4f-based heteronuclear Ni(II)2Dy(III)2 coordination clusters are also capable of reducing N2 electrochemically in an aqueous medium. Although there are several kinds of electrocatalysts known for eNRR, only a few metal-based molecular complexes/clusters were studied towards eNRR till to date. As they are structurally well-characterized using SC-XRD analysis and other modern tools, their explicit array of atoms/molecules in the system finds an easy way to understand any correlation that exists between the structure of the material to the eNRR activity.
References
[1] D. Liu, M. Chen, X. Du, H. Ai, K. H. Lo, S. Wang, S. Chen, G. Xing, X. Wang, H. Pan, Adv. Funct. Mater. 2021, 31, 2008983.