Benzothiadiazole (BT) directed C−H borylation using BCl3, followed by B−Cl hydrolysis and Suzuki–Miyaura cross-coupling enables facile access to twisted donor–acceptor compounds. A subsequent second C−H borylation step provides, on arylation of boron, access to borylated highly twisted D−A compounds with a reduced bandgap, or on B−Cl hydrolysis/cross-coupling to twisted D-A-D compounds. Photophysical studies revealed that in this series there is long lifetime emission only when the donor is triphenylamine. Computational studies indicated that the key factor in observing the donor dependent long lifetime emission is the energy gap between the S1/T2 excited states, which are predominantly intramolecular charge-transfer states, and the T1 excited state, which is predominantly a local excited state on the BT acceptor moiety.
- natural transition orbitals
- thermally activated delayed fluorescence