Computationally Guided Molecular Design to Minimize the LE/CT Gap in D-π-A Fluorinated Triarylboranes for Efficient TADF via D and π-Bridge Tuning

In this combined experimental and theoretical study, a computational protocol is reported to predict the excited states in D-pi-A compounds containing the B((F)Xyl)(2) ((F)Xyl = 2,6-bis(trifluoromethyl)phenyl) acceptor group for the design of new thermally activated delayed fluorescence (TADF) emitters. To this end, the effect of different donor and pi-bridge moieties on the energy gaps between local and charge-transfer singlet and triplet states is examined. To prove this computationally aided design concept, the D-pi-B((F)Xyl)(2) compounds 1-5 were synthesized and fully characterized. The photophysical properties of these compounds in various solvents, polymeric film, and in a frozen matrix were investigated in detail and show excellent agreement with the computationally obtained data. Furthermore, a simple structure-property relationship is presented on the basis of the molecular fragment orbitals of the donor and the pi-bridge, which minimize the relevant singlet-triplet gaps to achieve efficient TADF emitters.