Research Projects

Development of chiral supramolecular assemblies having boosted circular dichroism and circularly polarized luminescence (CPL) is important due to their promising applications in 3D displays, information storage, synthetic photochemistry etc. The crucial parameter to evaluate CPL is luminescence dissymmetry factor (glum). In the recent past, a variety of CPL active materials have been developed using metal centered complexes, chiral liquid crystals and through co-assembly of chiral organic molecules, however, there is limited information available to regulate the chirality handedness in excited state in supramolecular architectures produced through self-assembly of single building block and most of the studies have been performed in organic media. In the light of literature reports and our experience in this field, we have planned the synthesis of building blocks based on designs A-H. We chose -conjugated scaffold such as phenazine as the core due to their excellent photophysical properties. All the synthesized compounds are expected to undergo self-assembly in aqueous media through cooperative noncovalent interactions such as intramolecular/intermolecular hydrogen bonding interaction, π-π intermolecular stacking, hydrophobic effect etc. For boosting CPL activity, we are focusing on two approaches. The building blocks based on design A-F are expected to enhance chiroptical activity through increased rigidity at supramolecular level via interplay of primary and secondary interactions. We plan to investigate the subtle tunning of primary/secondary interactions through systematically changing the acceptor strength/ rigidity of the core and number of chiral handle units over the morphology and chirality transfer in at supramolecular level. The compounds based on designs A-F are expected to generate emissive rigid assemblies due to presence of rotatable groups and strength of secondary interactions which will influence the CPL activity. Additionally, by switching the -NH- of the carbamate units with -O-, we expect a change in the solute-solvent interactions which may also influence morphology/chirality transition at supramolecular level. The second approach for boosting chiroptical properties is through tunning of CT characteristics. Recently, PI’s research group reported development of twisted donor-acceptor building blocks which upon self-assembly generated emissive assemblies having strong absorption in 455–480 nm range in aqueous media that matches well with low-power visible excitation sources. The combination of a twisted intramolecular charge transfer (TICT) state and intermolecular charge transfer promoted the intersystem crossing (ISC) which is beneficial for stabilization of excited state and harvesting solar radiations. In view of literature reports and our experience in the field, we plan to examine the effect of donor-acceptor backbone over the chiroptical behaviour of derivatives based on designs G-H in excited state. Due to AIE active donor-acceptor scaffolds these materials are expected to show emission in long wavelength due to their charge transfer characteristics. Guided by the supramolecular non-covalent interactions, the synthesized materials are expected to generate chiral assemblies in mixed aqueous media. The impact of number and strength of donor/acceptor units will also be examined over the emission behaviour. The excited state chirality at supramolecular level will be examined by CPL. Thus, a series of building blocks will be prepared to understand the regulation of morphology modulation in living supramolecular polymers for attaining enhanced chiroptical properties. Promising candidates will be examined for their optoelectronic properties.