Details

Autor(en) / Beteiligte

• Stein, Laura
• Wang, Cui
• Förster, Christoph
• Resch-Genger, Ute
• Heinze, Katja

Titel

Bulky ligands protect molecular ruby from oxygen quenching

Ist Teil von

• Dalton transactions : an international journal of inorganic chemistry, 2022-11, Vol.51 (46), p.17664-1767

Ort / Verlag

Cambridge: Royal Society of Chemistry

Erscheinungsjahr

2022

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Chromium( iii ) complexes can show phosphorescence from the spin-flip excited doublet states 2 E/ 2 T 1 in the near-infrared with high photoluminescence quantum yields and extremely long lifetimes in the absence of dioxygen. The prototype molecular ruby, [Cr(ddpd) 2 ] 3+ (ddpd = N , N ′-dimethyl- N , N ′-dipyridine-2-ylpyridine-2,6-diamine), has a photoluminescence quantum yield and a luminescence lifetime of 13.7% and 1.1 ms in deaerated acetonitrile, respectively. However, its luminescence is strongly quenched by 3 O 2 via an efficient Dexter-type energy transfer process. To enable luminescence applications of molecular rubies in solution under aerobic conditions, we explored the potential of sterically demanding ddpd ligands to shield the chromium( iii ) center from O 2 using steady state and time-resolved photoluminescence spectroscopy. The structures of the novel complexes with sterically demanding ligands were investigated by single crystal X-ray diffraction and quantum chemically by density functional theory calculations. The O 2 sensitivity of the photoluminescence was derived from absolutely measured photoluminescence quantum yields and excited state lifetimes under inert and aerobic conditions and by Stern-Volmer analyses of these data. Optimal sterically shielded chromium( iii ) complexes revealed photoluminescence quantum yields of up to 5.1% and excited state lifetimes of 518 µs in air-saturated acetonitrile, underlining the large potential of this ligand design approach to broaden the applicability of highly emissive chromium( iii ) complexes. Steric protection strongly reduces phosphorescence quenching of excited molecular rubies by oxygen. The most bulky ligand enables photoluminescence quantum yields up to 5.1% and lifetimes up to 518 µs in air-saturated acetonitrile.