Supramolecular Approach for Fine-Tuning of the Bright Luminescence from Zero-Dimensional Antimony(III) Halides

Halides of ns2 metal ions have recently regained broad research interest as bright narrowband and broadband emitters. Sb(III) is particularly appealing for its oxidative stability (compared to Ge2+ and Sn2+) and low toxicity (compared to Pb2+). Square pyramidal SbX5 anion had thus far been the most common structural motif for realizing high luminescence efficiency, typically when cocrystallized with an organic cation. Luminescent hybrid organic-inorganic halides with octahedral coordination of Sb(III) remain understudied, whereas fully inorganic compounds show very limited structural engineerability. We show that the host-guest complexation of alkali metal cations with crown ethers fosters the formation of zero-dimensional Sb(III) halides and allows for adjusting the coordination number (5 or 6). The obtained compounds exhibit bright photoluminescence with quantum yields of up to 89% originating from self-trapped excitons, with emission energies, Stokes shifts, and luminescence lifetimes finely-adjustable by structural engineering. A combination of environmental stability and strong, intrinsic temperature-dependence of the luminescence lifetimes in the nanosecond-to-microsecond range nominate these compounds as highly potent luminophores for remote thermometry and thermography owing to their sensitivity range of 200-450 K and high specific sensitivities of 0.04 °C-1.