Trigonal Copper(I) Complexes with Cyclic (Alkyl)(amino)carbene Ligands for Single-Photon Near-IR Triplet Emission

Abstract

Molecular near-IR (NIR) triplet-state emitters are of importance for the development of new, organic-electronics-based telecommunication technologies as optical fibers operating in the corresponding spectral bands allow for data transfer over much longer distances due to the significantly lower attenuation. However, achieving such low-energy triplet excited states with good radiative rate constants is very challenging, and studies regarding the single-photon emission of organometallics in this energy range are scarce. We have prepared a series of trigonal CuI CAAC complexes bearing chelating ligands with O, N, S, and Se donor atoms and studied their photophysical properties in this context. The compounds show weak low-energy absorption in solution between 400 and 500 nm due to mixed Cu → CAAC 1MLCT/LLCT states, resulting in yellow-green to orange appearance, which we have also correlated to the 15N NMR resonances of the π-accepting carbene ligand. In the solid state, phosphorescence from dominant 3(Cu → CAAC) CT states is observed at room temperature. The emission of the complexes is bathochromically shifted in comparison to structurally related linearly coordinated copper­(I) CAAC complexes due to structural reorganization in the excited state to a T-shape. For [Cu­(dbm)­(CAACMe)], the broad phosphorescence with outstanding λmax = 760 nm tailors out to ca. 1100 nm and leads to its proof-of-concept application as a nonclassical single-photon light source, constituting key functional units for the implementation of tap-proof data transfer.

An Air‐ and Moisture‐stable Zinc(II) Carbene Dithiolate Dimer Showing Fast Thermally Activated Delayed Fluorescence and Dexter Energy Transfer Catalysis**

“…An alternative is to employ metal centres in their d 0 or d 10 electron configuration [10,18–23] . This approach provides the additional advantage of various coordination spheres of the same metal centre being accessible, which greatly influences the nature, energy and reactivity of the excited states.…”

Photoactive Copper Complexes: Properties and Applications

“…New three-coordinate carbene complexes based on the Me CAAC ligand ( C 29 ) and several chelating ligands with coordinating chalcogen atoms have been reported. Two complexes bearing respectively NN - or NO -chelating ligand demonstrated near-IR emission centered around 740−760 nm, a valuable property allowed by going from linear to trigonal coordination geometry and by the large reorganization happening at the excited state for these complexes . Five two-coordinate carbene-copper-amide complexes based on a carbene related to C 10 and carbazole ligands were synthesized and applied to OLED devices .…”

Trendbericht: Photochemie

“…Dies ermöglichte den Wechsel von linearen zu dreifach koordinierten Komplexen (Abbildung 2). 25) Interessanterweise emittieren die Cu I -Komplexe mit einem O^Ooder N^N-Liganden im Roten schwach, aber die breiten Emissi-onsbanden erstrecken sich im Festkörper bis tief in den NIR-Bereich, zirka bis 1100 nm. Darüber hinaus eignen sich diese Komplexe potenziell als nichtklassische Einzelphotonenlichtquelle für organische Elektronik.…”