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Six conjugates of benzoxazole and green fluorescent protein chromophore that differ by the length of their alkyl chain (from C1 to C16) are investigated. They exhibit rigidofluorochromism and clear aggregation-induced emission enhancement (AIEE) behavior with emission in the orange-red that is specific to the solid state. A preparation method based on solvent exchange is used to prepare particles. The self-association properties of these molecules depend on the length of the alkyl chain. Microfibers, platelets, and rounded microparticles are successively obtained by increasing the chain length. The same method is used to prepare nanoparticles (NPs) that are fully characterized. In particular, homogeneous populations of stable NPs measuring around 70 nm are obtained with the analogs whose chains contain four to eight carbon atoms. The behavior with respect to living cells is also influenced by the nature of the compounds. Only the dyes with intermediate hydrophobicity are efficiently uptaken by both normal and tumor cells, and fluorescence only originates from dispersed dye molecules. There is no evidence for incorporation of NPs into cells. This work shows that small variations of the chemical structure must be taken into account for making the best use of AIEE compounds in view of precise applications., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

2-Phenyl-benzoxazole and five derivatives bearing an alkyl or alkoxy substituent on the phenyl ring were used to prepare aqueous suspensions of particles via a solvent-exchange method. In these conditions, the methyl and methoxy derivatives spontaneously gave nanofibers, while the other compounds led to microcrystals. This shows that minor chemical changes are enough to direct the formation of a given type of particle. From a spectroscopic viewpoint, all compounds strongly emit blue light in the solid state, with spectra much broader than those registered in n-heptane and ethanol solutions. The photoluminescence quantum yields reached 38% and were slightly affected in aqueous suspension by the polarity of the environment. The molecular arrangement, deduced from X-ray analysis for the methyl and methoxy derivatives, was used to explain the fluorescence properties in the solid state. This work shows that 2-phenyl-benzoxazole derivatives are interesting candidates for applications as fluorescent nanomaterials, including in aqueous and biological media.