Dinuclear Ag(I) Complex Designed for Highly Efficient Thermally Activated Delayed Fluorescence

The dinuclear Ag­(I)
complex has been designed to show thermally
activated delayed fluorescence (TADF) of high efficiency. Strongly
electron-donating terminal ligands are introduced to destabilize the
d orbitals of the Ag+ ions. Consequently, the orbitals
distinctly contribute to the HOMO, whereas the LUMO is localized on
the bridging ligand. This ensures charge transfer character of the
lowest excited singlet S1 and triplet T1 states.
Accordingly, a small energy gap ΔE(S1–T1) is obtained, being essential for TADF behavior.
Photophysical investigations show that at ambient temperature the
complex exhibits TADF reaching a quantum yield of ΦPL = 70% with the decay time of only τ = 1.9 μs, manifesting
one of the fastest TADF decays observed so far. Such an outstanding
TADF efficiency is based on a small value of ΔE(S1–T1) = 480 cm–1 combined with a large transition rate of k(S1 → S0) = 2.2 × 107 s–1.