A Highly Luminescent Metallo-Supramolecular Radical Cage

Abstract

Luminescent metal-radicals have recently received increasing attention due to their unique properties and promising applications in materials science. However, the luminescence of metal-radicals tends to be quenched after formation of metallo-complexes. It is challenging to construct metal-radicals with highly luminescent properties. Herein, we report a highly luminescent metallo-supramolecular radical cage (<b>LMRC</b>) constructed by the assembly of a tritopic terpyridinyl ligand <b>RL</b> with tris(2,4,6-trichlorophenyl)methyl (TTM) radical and Zn²⁺. Electrospray ionization-mass spectrometry (ESI-MS), traveling-wave ion mobility-mass spectrometry (TWIM-MS), X-ray crystallography, electron paramagnetic resonance (EPR) spectroscopy, and superconducting quantum interference device (SQUID) confirm the formation of a prism-like supramolecular radical cage. <b>LMRC</b> exhibits a remarkable photoluminescence quantum yield (PLQY) of 65%, which is 5 times that of <b>RL</b>; meanwhile, <b>LMRC</b> also shows high photostability. Notably, significant magnetoluminescence can be observed for the high-concentration <b>LMRC</b> (15 wt % doped in PMMA film); however, the magnetoluminescence of 0.1 wt % doped <b>LMRC</b> film vanishes, revealing negligible spin-spin interactions between two radical centers in <b>LMRC</b>.