A Vanadium(III) Complex with Blue and NIR-II Spin-Flip Luminescence in Solution

• DOI: 10.1021/jacs.0c02122
• Publication Date: 2020-04-10T15:30:08Z
• Authors: Matthias 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
• Keywords: ELECTRONIC-STRUCTURE; SPECTROSCOPY; STATES; 104017 Physical chemistry; TELECOMMUNICATIONS; RUBY; LANTHANIDE; 104003 Anorganische Chemie; DECAY; 01 natural sciences; 104017 Physikalische Chemie; 104003 Inorganic chemistry; 0104 chemical sciences

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.