Chiral Carbene Zinc(II) Dithiolates: Efficient TADF Emitters Showing Circularly Polarized Luminescence

27 October 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Luminescent metal complexes based on earth abundant elements are a valuable target to substitute 4d/5d transition metal complexes as triplet emitters in advanced photonic applications. Whereas Cu(I) complexes have been thoroughly investigated in the last two decades for this purpose, no structure-property-relationships for efficient luminescence involving triplet excited states from ZnII complexes are established. Herein, we report on the design of monomeric carbene zinc(II) dithiolates (CZT) featuring a donor-acceptor-motif that leads to highly efficient thermally activated delayed fluorescence (TADF) with for Zn(II) compounds unprecedented radiative rate constants k(TADF) = 1.2x10^6 s^-1 at 297 K. Our high-level DFT/MRCI calculations revealed that the relative orientation of the ligands involved in the ligand-to-ligand charge transfer (1/3^LLCT) states is paramount to control the TADF process. Specifically, a dihedral angle of 36-40° leads to very efficient reverse intersystem-crossing (rISC) on the order of 10^9 s^-1 due to spin–orbit coupling (SOC) mediated by the sulfur atoms in combination with a small E(S1-T1) of ca. 56 meV (calc. 20 meV). In addition, the chiral carbene ligand leads to the generation of circularly polarized luminescence (CPL) with high dissymmetry values g(lum) of up to 3.3x10^-2 in polystyrene (PS).


Thermally Activated Delayed Fluorescence
Circularly polarized luminescence

Supplementary materials

Supporting Information
Details of synthesis, characterization, additional spectra, photophysical data, and computational results


Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.