Programmable Supramolecular Polymerization in Chiral Naphthalene Diimide (NDI) Systems: Role of Directional H-Bonding & External Triggers

Khan, Sayantan (2025) Programmable Supramolecular Polymerization in Chiral Naphthalene Diimide (NDI) Systems: Role of Directional H-Bonding & External Triggers. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (Sayantan Khan Institute (20MS041)) 20MS041_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (2MB)

Abstract

Supramolecular chirality, as an emerging domain in functional materials design, offers unique opportunities to regulate molecular self-assembly through non-covalent interactions. In this study, a chiral naphthalene diimide (NDI) derivative (NDH), equipped with orthogonal hydrogen bond donors at both imide (-NHI) and amide (-NHA) positions, was investigated to understand its pathway complexity in aqueous media. Time-dependent UVVis and CD spectroscopy in a DMSO–H2O (1:1) mixture revealed a kinetically evolving selfassembly from an initial intermediate aggregate (Agg 1) to a more stable aggregate (Agg 2), supported by twisted nanofiber morphologies. In addition, concentration-dependent kinetic studies further highlighted the presence of competing aggregation pathways. Addition of a chemoselective trigger, DBU enabled selective imide deprotonation, halting kinetic progression or reversing aggregation, thereby demonstrating the key role of imide hydrogen bonding in structural evolution and reversibility. A comparison with an anhydride analogue (NDO), lacking the imide proton, confirmed a simplified, single-pathway aggregation behavior. Compiling together, these observed results underscore how orthogonal hydrogenbonding motifs and π- π stacking synergistically govern supramolecular chirality and kinetic control in π-conjugated systems.

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