posted on 2020-04-16, 21:45authored byMatthias Dorn, Jens Kalmbach, Pit Boden, Ayla Päpcke, Sandra Gómez, Christoph Förster, Felix Kuczelinis, Luca M. Carrella, Laura A. Büldt, Nicolas H. Bings, Eva Rentschler, Stefan Lochbrunner, Leticia González, Markus Gerhards, Michael Seitz, Katja Heinze
Luminescence
from Earth-abundant metal ions in solution at room
temperature is a very challenging objective due to the intrinsically
weak ligand field splitting of first-row transition metal ions, which
leads to efficient nonradiative deactivation via metal-centered states.
Only a handful of 3dn metal complexes
(n ≠ 10) show sizable luminescence at room
temperature. Luminescence in the near-infrared spectral region is
even more difficult to achieve as further nonradiative pathways come
into play. No Earth-abundant first-row transition metal complexes
have displayed emission >1000 nm at room temperature in solution
up
to now. Here, we report the vanadium(III) complex mer-[V(ddpd)2][PF6]3 yielding phosphorescence
around 1100 nm in valeronitrile glass at 77 K as well as at room temperature
in acetonitrile with 1.8 × 10–4% quantum yield
(ddpd = N,N′-dimethyl-N,N′-dipyridine-2-ylpyridine-2,6-diamine).
In addition, mer-[V(ddpd)2][PF6]3 shows very strong blue fluorescence with 2% quantum
yield in acetonitrile at room temperature. Our comprehensive study
demonstrates that vanadium(III) complexes with d2 electron
configuration constitute a new class of blue and NIR-II luminophores,
which complement the classical established complexes of expensive
precious metals and rare-earth elements.