Studies of Multi-functional Metal-Organic Frameworks and Complexes using Polycarboxylic Acids and pyrazole based Ligands

The design and synthesis of polyhedral coordination cages1 has become a major part of research endeavour in recent years. The supramolecular coordination complexes (SCCs) refer to discrete metallacycles and metallacages which can be obtained by self-assembly reactions. A coordination cage can be defined as a type of coordination compounds with cavities that can engage in host-guest chemistry.2 They usally consist of several metal centres connected with organic ligands. Early efforts in the development of coordination-driven self-assembly reactions and the formation of SCCs were largely structural in nature. The major aim to achieve specific metallacycles and cages through various, now well-defined, assembly strategies including edge-directed, face-directed, symmetry-adapted, and weaklink approaches, all unified under the theme of ―directional bonding‖. Many of these methods are rooted in two component assemblies, wherein one metal acceptor and one organic donor are used in specific ratios to form highly symmetric metallacycles or cages, with examples spanning many polygons and polyhedra. The metallacycles and metallacages are very useful in host-guest chemistry, apart from that they are also well documented in the literature in molecular sensors, in luminescence, molecular optics, magnetism, homo and heterogeneous catalysis etc.The studies of polynuclear lanthanide based cage complexes are at the early stage of research. Polynuclear lanthanide cages or clusters have attracted research interest because of their versatile architecture (geometry) and photophysical properties. Polynuclear lanthanide cages or clusters have widespread applications in sensors, labels for biomolecules, stains for cellular imaging, display devices, redox-active switches, magnetocaloric effects and single molecule magnets (SMMs). Due to the magnetic anisotropy arising from large unquenched orbital angular momentum and unpaired f-electrons lanthanide complexes (especially Dy) are excellent candidate for the high energy barrier for reversal of magnetization.3 On the other hand, molecular magnetic materials which show large magnetocaloric effect (MCE)4 are of 9 immense research interest for their cryogenic applications. Gd3+ ion one of the most commonly found element which are well documented in the literature having large magneto caloric effect (MCE). Such kind of fascinating properties arises due to large spin-only magnetic moment (S=7/2), quenched orbital momentum and weak super exchange interactions which is responsible for a large entropy change. Therefore it has been found that Gd(III) based complexes showed super cooling properties for magnetic based coolants with highly entropy change value.The research was conducted under the supervision of Dr. Raju Mondal of Inorganic Chemistry under SCS [School of Chemical Sciences]The research was conducted under CSIR grant and fellowshi