Research Projects

The branch of supramolecular chemistry that concerns the fabrication of 2D/3D discrete architectures for stabilizing guest molecules within their cavities is a mature field of research. The ability of these architectures to house guests within their internal pockets has led to the emergence of several applications such as catalysis in confined spaces, molecular separations via selective encapsulation, etc. Upgrading such applications for industrial-level implementations demands that synthetic techniques must be simple, the processes must be efficient, and at the same time green. The latter attribute requires that the host cages employed for the applications must be soluble in water, the medium of life. Coordination-driven self-assembly is a simple technique often utilized to synthesize water-soluble Pd(II)/Pt(II) cages. Since the first report of a water-soluble, octahedral Pd6L4 cage, self-assembled from a 90º Pd(II) acceptor and tri-pyridine ligand by Fujita and co-workers, the aforementioned host or similar Pd(II)/Pt(II) octahedral cages have been utilized as molecular nanoreactors or for other applications by Fujita, Mukherjee’s group and several others. In this proposal we aim to introduce urea moieties within tritopic ligands so as to carry out urea assisted organic transformations within the confined cavities of octahedral cages in aqueous media. Further, carrying out enantio-selective transformations within confined spaces is a challenging task and has hardly been achieved. This is mainly due to the difficulty of inducing chirality into the nano-spaces. Chiral octahedral hosts can be designed from chiral Pd(II)/Pt(II) acceptors that may induce chirality to the C3-symmetric tritopic ligands upon self-assembly, generating homochiral cages. However, the chiral induction is sometimes weak rendering asymmetric synthesis within the cavities challenging. Thus, here we propose the synthesis of chiral octahedral hosts from chiral ligands that would effectively make the whole octahedral cavity chiral without the need for chiral induction. Another challenging aspect in confined space catalysis is product inhibition. Barrel-like architectures, designed from tetradentate ligands and 90º Pd(II)/Pt(II) acceptors possess cylindrical cavities with two wide-open portals that ensure such architectures not only stabilize guest molecules but also facilitate product expulsion from the internal pockets, post- reaction. This proposal also concerns synthesis of such chiral hosts from enantiopure “spinol-phosphonate” based functionalized tetratopic ligands carrying out enantioselective transformations. Charged-organic cages/macrocycles synthesized using covalent techniques constitute another class of water-soluble hosts that possess electron-deficient and shape-persistent cavities ideal for stabilizing a wide variety of electron-rich guests. This proposal concerns the synthesis of such metal-free, charged systems via SN2 and Zincke reactions for carrying out confined space catalysis. Furthermore, we aim to synthesize chiral charged hosts from chiral building units with an eye towards applications such as resolution of enantiomers or advanced applications like generation of circularly polarized luminescence (CPL) via transfer of chirality from host to encapsulated achiral dyes. In summary, this original and creative research proposal focuses on the design and development of water-soluble hosts for applications such as molecular separation and catalysis within their confined cavities. A key objective is to introduce chirality into these architectures by incorporating chiral building blocks, enabling their use in chiral resolution and asymmetric synthesis. Additionally, the proposal aims to explore applications, such as circularly polarized luminescence (CPL), by facilitating chirality transfer from the chiral host to encapsulated achiral dye molecules.