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Effect of Differential Self-Assembly on Mechanochromic Luminescence of Fluorene-Benzothiadiazole-Based Fluorophores

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Version 2 2021-09-27, 18:05
Version 1 2017-12-19, 13:39
journal contribution
posted on 2017-12-19, 13:39 authored by Karattu Chali Naeem, Kadaikkara Neenu, Vijayakumar C. Nair
Supramolecular self-assembly is an excellent tool for controlling the optical and electronic properties of chromophore-based molecular systems. Herein, we demonstrate how differential self-assembly affects mechanoresponsive luminescence of fluorene-benzothiadiazole-based fluorophores. We have synthesized two donor–acceptor–donor-type conjugated oligomers consisting of fluorene as the donor and benzothiadiazole as the acceptor. For facile self-assembly, both molecules are end-functionalized with hydrogen-bonding amide groups. Differential self-assembly was induced by attaching alkyl chains of different lengths onto the fluorene moiety: hexyl (FB-C6) and dodecyl (FB-C12). The molecules self-assemble to form well-defined nanostructures in nonpolar solvents and solvent mixtures. Although their optical properties in solution are not affected by the alkyl chain length, significant effects were observed in the self-assembled state, particularly in the excitation energy migration properties. As a result, remarkable differences were observed in the mechanochromic luminescence properties of the molecules. A precise structure–property correlation is made using UV–visible absorption and fluorescence spectroscopy, time-correlated single-photon counting analysis, scanning electron microscopy, and X-ray diffraction spectroscopy.

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