1. Self-reversible mechanofluorochromic AIEgens with tunable solid-state fluorescence: effect of acceptors and intermolecular interactions.
- Author
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Ravi, Sasikala, Priyadharsan, R. Rameshbabu, Karthikeyan, Subramanian, Pannipara, Mehboobali, Al-Sehemi, Abdullah G., Moon, Dohyun, and Anthony, Savarimuthu Philip
- Subjects
FRONTIER orbitals ,INTRAMOLECULAR charge transfer ,MOLECULAR conformation ,INTERMOLECULAR interactions ,CRYSTAL lattices - Abstract
Exploring the organic molecular structural features and supramolecular interactions provide basis for developing stimuli-responsive organic solid-state fluorescent materials. Herein, we have synthesized methoxyphenyl-substituted carbazole-based π-conjugated derivatives (Cz-MN, Cz-ECA, Cz-CA, Cz-CAA and Cz-NBA) with different acceptor units and investigated their influence on solid-state fluorescence. All five compounds showed aggregation-induced emission (AIE) in the solid state with acceptor-dependent tunable fluorescence from 488 to 602 nm (quantum yield (Φ
f ) = 7.2 to 1.9%). Cz-ECA exhibited blue-shifted fluorescence, whereas Cz-NBA showed red-shifted fluorescence. Cz-MN, Cz-ECA and Cz-CA revealed relatively strong solid-state fluorescence compared to Cz-CAA and Cz-NBA. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) calculations suggested intramolecular charge transfer (ICT) from the carbazole donor to the acceptor unit. Mechanofluorochromic studies of Cz-MN and Cz-ECA showed self-reversible fluorescence switching but the other three AIEgens did not show any stimuli–response. Single crystal structural analysis of Cz-MN, Cz-ECA and Cz-CA showed twisted molecular conformations with different intermolecular interactions. Both Cz-MN and Cz-ECA did not show any strong intermolecular interactions in the crystal lattice. In contrast, Cz-CA exhibited strong amide–amide complementary H-bonding and an extended network structure. Hence, the twisted molecular conformation and the absence of strong intermolecular interactions in Cz-MN and Cz-ECA contributed to self-reversible mechanofluorochromism (MFC). Thus, the present study is expected to provide further insight to design AIEgens with stimuli-responsive self-reversible fluorescent materials. [ABSTRACT FROM AUTHOR]- Published
- 2024
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