Topological effect on fluorescence emission of tetraphenylethylene-based metallacages

Herein, we describe the selective formation of a barrel-shaped or a ball-shaped fluorescent metallacage by controlling the shape and stoichiometry of the building blocks. Specifically, the tetraphenylethylene-based donor and two acceptors with different numbers of Pt(II) centers were combined via coordination-driven self-assembly. Owing to the differences in the shapes of the assemblies, the resultant ball-shaped metallacage displayed stronger and blue-shifted fluorescence compared to the barrel-shaped one in dilute solutions, while a reversal of fluorescence intensities was observed in the aggregation process. Overall, this work demonstrates that the photophysical properties of supramolecular coordination complexes can be affected by subtle geometrical factors, which can be controlled precisely at the molecular level. Though the coordination-driven self-assembly, we exploited the same TPE-based donor to selectively construct two metallacages with distinct geometries (barrel or ball shape) by varying the Pt acceptors. Notably, due to the differences in the topological structures of these assemblies, the barrel-shaped metallacages showed weaker and red-shifter fluorescence-emission relative to the ball-shaped ones, whereas exhibiting a more pronounced enlarged amplitude of fluorescence intensity upon the aggregation. [Display omitted]