Probing the Formation of Metal–Organic Cages by Electrochemiluminescence

It
is important to probe the formation of metal–organic
cages (MOCs) to ensure their versatility. Currently, the formation
of MOCs is commonly characterized by using single-crystal X-ray diffraction,
mass spectrometry, and nuclear magnetic resonance. However, the application
scopes of these techniques are limited because they require that MOCs
have high-quality single crystals, excellent solubility, and superior
stability. In this work, we introduced an electrochemiluminescence
(ECL) method to rapidly probe the formation of palladium-based MOCs.
It was demonstrated that the formation of the Pd2L4 MOCs could lead to a significant increase in charge transfer
resistance and a noticeable change in surface charge, resulting in
substantial quenching (up to 99.1%) of the ECL signal in the Ru(bpy)32+/tripropylamine (TPA) system. This innovative
“signal-off” ECL sensing mechanism allowed for a fast
and ultrasensitive identification of MOC formation. Our findings not
only provide a robust strategy for rapid characterization of supramolecular
assemblies but also open new avenues for extending ECL-based analytical
techniques to the study of other crystalline materials.