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

A dimeric Zn-II carbene complex featuring bridging and chelating benzene-1,2-dithiolate ligands is highly stable towards air and water. The donor-Zn-acceptor structure leads to visible light emission in the solid state, solution and polymer matrices with lambda(max) between 577-657 nm and, for zinc(II) complexes, unusually high radiative rate constants for triplet exciton decay of up to k(r)=1.5x10(5) s(-1) at room temperature. Variable temperature and DFT/MRCI studies show that a small energy gap between the (LL)-L-1/3/LMCT states of only 79 meV is responsible for efficient thermally activated delayed fluorescence (TADF). Time-resolved luminescence and transient absorption studies confirm the occurrence of long-lived, dominantly ligand-to-ligand charge transfer excited states in solution, allowing for application in Dexter energy transfer photocatalysis.

Automated summary

This article reports a dimeric Zn-II carbene complex with bridging and chelating benzene-1,2-dithiolate ligands, which is highly stable towards air and water. The complex exhibits visible light emission in the solid state, solution, and polymer matrices, with a maximum wavelength between 577-657 nm. It also shows unusually high radiative rate constants for triplet exciton decay at room temperature. The efficient thermally activated delayed fluorescence (TADF) of the complex is attributed to a small energy gap between the (LL)-L-1/3/LMCT states. Time-resolved luminescence and transient absorption studies confirm the presence of long-lived, dominantly ligand-to-ligand charge transfer excited states in solution, allowing for application in Dexter energy transfer photocatalysis.