Research Projects

Switchable semiconductor is an important research topic that has implication in solar cells, transistors, thermoelectrics, sensors etc. The project proposal aimed to develop photo-switchable aqueous metallosupramolecular polymers and co-polymers with intermolecular homo- and hetero-metallophilic interactions, respectively and investigate their photo-regulated electrical conductivity. Firstly, self-assembly of rationally designed discrete metal complexes will be studied in aqueous media. Once the experimental and structural parameters required for controlled supramolecular polymerization involving stable homo- and hetero-metallophilic interaction is optimized, next deliverable will be to broaden the scope by introducing photochromic switch in the molecular design. The ultimate goal will be to investigate the interplay between photoisomerization and metallophilic interactions on controlling the pathway complexity, and hence electrical properties of metallosupramolecular polymers. Briefly, the implementation of the project will involve the following steps: 1) d8 transition metal complexes (mostly Pt(II), Pd(II)) of mono- and polydentate N-heterocyclic aromatic ligands functionalized with amide or bis-amide linkage and triethyleneglycol (TEG) side chains will be synthesized. Such molecular design will ensure aggregation in aqueous media via complementary intermolecular interactions (H-bonding and π-π stacking), and will help in maximizing the metal-metal contact in the 1D aggregates. 2) Detailed investigations on self-assembly process will be carried out by variable temperature (VT) UV/Vis, 1H-NMR and dynamic light scattering (DLS) studies. Atomic force microscopy (AFM) and Scanning Electron Microscope (SEM) will be used to visualize the nano/meso structures of the aggregates. Combined 1D and 2D NMR studies will shine light on the supramolecular interactions and molecular packing associated with the aggregation. 3) The homo-and hetero-metallophilic interactions (Pt(II)···Pt(II) and Pt(II)···Pd(II)) in the polymers and co-polymers will be probed by detailed photophysical (phosphorescence, lifetime) and Raman analysis. Tuning experimental parameters and structural modifications (if, necessary) will help to achieve stable metal-metal contacts in the 1D aggregates. 4) Electrical conductivity of these polymers and co-polymers will be measured using sourcemeter. 5) Finally, photochromic switch (such as, azobenzene) will be introduced in the molecular design of polymers and co-polymers. Geometrical change associated with the photoisomerization will reversibly affect the metallophilic interactions. By switching on/off the metallophilic interaction (by UV/Vis light), electrical conductivity of these polymers will be regulated. This unprecedented approach to create light-responsive conducting metallosupramolecular polymers will be a step forward towards switchable supramolecular electronics.