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Large Red-Shifted Fluorescent Emission via Intermolecular π–π Stacking in 4‑Ethynyl-1,8-naphthalimide-Based Supramolecular Assemblies

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journal contribution
posted on 07.10.2014, 00:00 by Xinhua Cao, Luyan Meng, Zhenhua Li, Yueyuan Mao, Haichuang Lan, Liming Chen, Yang Fan, Tao Yi
Two low molecular weight gelators containing 4-ethynyl-1,8-naphthalimide groups with large conjugated structure via different length of alkyl chains were synthesized and fully characterized. The gelation properties, structural character, and fluorescence of the gels were investigated via methods of scanning electron microscopy, X-ray diffraction, and spectral studies. The gelators have high fluorescence quantum yields in both solution and solid state. Interestingly, the wavelength of the fluorescent emission in the reversible sol–gel transition process of the gels has a large red-shift of 80 nm in DMF, which is extremely sparse for 1,8-naphthalimide derivatives in the literature. The intermolecular π–π stacking between naphthalimide is suggested to be the main driving force for the gel formation and fluorescent variation by means of temperature-dependent 1H NMR study and theoretical calculation.