Oxygen and sulfur-based pure n-electron dendrimeric systems: generation-dependent clusteroluminescence towards multicolor cell imaging and molecular ruler

Dendrimers, as the latest generation of artificial macromolecules, have aroused great attention in the field of clusteroluminescence owing to their unique structural and photophysical features. However, previously reported dendrimers with cluster-oluminescenence property usually contain πelectrons-involved carbonyl groups and/or environment-sensitive aliphatic amine moieties in their structures, thus complicating the interpretation of the emission process. On the other hand, a systematic investigation on the luminescence performance of dendrimers with diverse generations is significantly important for the researchers to gain further mechanistic insights into the clusteroluminescence, but has still been scarcely touched. In this contribution, we reported a series of oxygen and sulfur-based pure n-electron dendrimers with different generations from G1 to G3. Benefiting from the highly-branched three-dimensional crowded molecular structures, all these dendrimers exhibited bright fluorescence emission in visible light region due to their prominent clusteroluminescence property. Moreover, the fluorescence intensity and emission wavelength were simultaneously boosted as their generation increased due to the more crowded molecular architectures, as well as the formation of tighter and larger clusters at higher generation. Besides, these dendrimers also showed concentration- and aggregation-enhanced luminescence behaviors, presenting typical aggregation-induced emission (AIE) nature. Coupled with remarkable water solubility and biocompatibility as well as the excellent photostability, the G3 dendrimer selected as a representative was successfully applied in the multicolor cell imaging. In addition, the G3 dendrimer was also proved to be capable of acting as a molecular ruler to detect specific-sized molecule in aqueous solutions. This work not only validated the rationality of the clusteroluminescence mechanism but also offered high-performance clusteroluminogens for practical application.