Photo magnetic Investigation and Magneto-structural Correlation of Switchable Molecular Magnetic Materials

Abstract

Modern life without magnetic materials is almost impossible to imagine. Mobile phones, telecommunication, navigation, computer, television, credit cards, medical equipment, data storage devices, and sensors are an integral part of modern life. The demand and supply ratio of data storage devices is increasing day by day. To mitigate this, tremendous effort is required toward the synthesis and development of high-density data storage devices. Molecular systems exhibiting bistability i.e., a controlled and reversible change in their physical properties by external stimuli have a tremendous possibility in molecular-scale electronics e.g., data storage device, molecular qubits, quantum technology, molecular spintronics, and nanotechnological application. In particular, molecular magnetism is a rapidly growing field where molecules exhibiting photo- and thermo-chromism are of potential interest. In this thesis, I have adopted a unique ‘complex as a ligand’ strategy to rationally design and synthesize switchable molecular magnetic materials which exhibit interesting physical properties such as single-molecule magnet (SMM), spin crossover (SCO), metal-tometal electron transfer (MMET) and electrical and thermal conductivity. A series of new multifunctional homo-/hetero-bimetallic [Fe2Co2], [Fe2Fe2], and [Fe2Mn2] complexes have been synthesized using a molecular approach. To understand better the contributing factors for MMET properties, for example, ligand field effect, cooperativity, crystal matrix, and electronic factors, we have performed detailed structural, magnetic, optical, spectroscopic, and other physical characterization. Interestingly, some of these systems show interesting on/off photo-switching and thermo- and photo-induced hysteresis effects. I have performed a detailed study of the photo-induced metastable state along with the high-temperature magneto-structural investigation. In other parts of my thesis, I have studied the singlemolecule magnet behavior in highly anisotropic Co(II) complexes and the spin state switching behavior in Co(II) mono- and polymeric systems. In the last part of my thesis, I have coupled both spin crossover and luminescence properties in a coordination polymer in which concomitant change in both spin state and luminescence has been observed. Finally, I have discussed the application of these switchable materials in optoelectronic devices.