Boron Difluoride β-Diketonates: Structure and Phosphorescence

Phosphorescence data on boron difluoride β-diketonates of various structure have been systematized. Nonplanar boron difluoride molecules are characterized by the inversion of the S1 and T2 levels, which promotes efficient population of triplet levels and intense phosphorescence or delayed fluorescence of crystals. Planar molecules are characterized by a classical sequence of singlet and triplet levels and a coplanar arrangement of antiparallel molecules, which contributes to excimer delayed fluorescence.