Thesis Defense: Synthesis and Physicochemical Characterizations of 3d Transition MetalBased Anisotropic Complexes: A Building Block Approach for Designing Multifunctional Materials

Molecule-based magnetic materials have recently been a popular choice for generating multifunctional materials¹. An inherent property in such systems is molecular bistability, which enables a system to interchange between two easily accessible states (spin or magnetic) through the controlled application of external stimuli². Multifunctional magnetic materials³ have fascinating applications in information storage⁴, spintronics⁵, and quantum computing⁶. A suitable synthetic procedure for such molecular magnetic systems entails a so-called “bottom-up” building block approach, where anisotropic monometallic complexes function as the elementary unit. All these molecule-based magnetic materials exhibit several intriguing properties, such as Spin Crossover (SCO)⁷, Single Molecule Magnets (SMMs)⁸, Single Chain Magnets (SCMs), Magnetic Sponge, and Linkage Isomerism⁹ behavior. In my thesis, I first synthesized a series of macrocyclic porphyrin-based monometallic systems to look for the possibility of these molecules functioning as molecular magnets. Detailed spectroscopic, electrochemical, magnetic, and theoretical studies have been performed on these systems to clearly understand their feasibility as viable multifunctional molecular magnets. Following this, I have studied the effect of ligand field strength on the magnetic anisotropy and relaxation behavior in a series of mono- and dinuclear high-spin Co(II) complexes¹⁰. Thereafter, I would like to use these highly anisotropic Co(II) metal complexes for the synthesis of SCMs. Next, I have explored the molecular magnetic sponge-like behavior in a family of heterobimetallic cyano-bridged [CrMn] coordination networks, where adsorption and desorption of solvent molecules play a crucial role in the magnetic properties.¹¹ In the last part of my thesis, photo- and thermo-induced spin crossover properties have been investigated in a few heterobimetallic cyano-bridged [Cr2Fe3] multifunctional molecular clusters where the linkage isomerism property has been simultaneously observed.¹² Finally, I would conclude my talk by giving an outlook on the probable applications of the above-mentioned systems in devices and quantum qubits.