Singlet-Triplet Inversions in Through-Bond Charge-Transfer States
Molecules where the lowest excited singlet state is lower in energy than the lowest triplet are highly promising for a number of organic materials applications as efficiency limitations stemming from spin statistics are overcome. All molecules known to possess such singlet-triplet inversions exhibit a pattern of spatially alternating but nonoverlapping HOMO and LUMO orbitals, meaning the lowest excited states are of a local character. Here, we demonstrate that derivatives of the bicyclic hydrocarbon calicene exhibit Hund’s rule violations in charge-transfer (CT) states between its rings. These CT states can be tuned with substituents, so that the first excited singlet and triplet state are energetically inverted. This provides a conceptual connection between the emerging fields of inverted gap molecules and existing molecular design rules for state-of-the-art thermally activated delayed fluorescence materials.
2-s2.0-85205906359
39325862
École Polytechnique Fédérale de Lausanne
École Polytechnique Fédérale de Lausanne
École Polytechnique Fédérale de Lausanne
2024-10-10
15
40
10062
10067
REVIEWED
EPFL