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.