Premium
[Cr(ddpd) 2 ] 3+ : A Molecular, Water‐Soluble, Highly NIR‐Emissive Ruby Analogue
Author(s) -
Otto Sven,
Grabolle Markus,
Förster Christoph,
Kreitner Christoph,
ReschGenger Ute,
Heinze Katja
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201504894
Subject(s) - phosphorescence , intersystem crossing , ligand (biochemistry) , chromium , photochemistry , fluorescence , metal , diamine , ligand field theory , chemistry , materials science , excited state , atomic physics , physics , optics , polymer chemistry , ion , organic chemistry , biochemistry , receptor , singlet state
Abstract Bright, long‐lived emission from first‐row transition‐metal complexes is very challenging to achieve. Herein, we present a new strategy relying on the rational tuning of energy levels. With the aid of the large N‐Cr‐N bite angle of the tridentate ligand ddpd ( N , N ′‐dimethyl‐ N , N ′‐dipyridine‐2‐ylpyridine‐2,6‐diamine) and its strong σ‐donating capabilities, a very large ligand‐field splitting could be introduced in the chromium(III) complex [Cr(ddpd) 2 ] 3+ , that shifts the deactivating and photoreactive 4 T 2 state well above the emitting 2 E state. Prevention of back‐intersystem crossing from the 2 E to the 4 T 2 state enables exceptionally high near‐infrared phosphorescence quantum yields and lifetimes for this 3d metal complex. The complex [Cr(ddpd) 2 ](BF 4 ) 3 is highly water‐soluble and very stable towards thermal and photo‐induced substitution reactions and can be used for fluorescence intensity‐ and lifetime‐based oxygen sensing in the NIR.