In addition, derivatives of PDBA belong to either highly endergonic and thermally forbidden or highly exergonic, so the vibration process cannot be reversible due to the Bell-Evans-Polanyi principle. Chou et al. combined the opposite destabilization effect from a thermodynamic perspective with molecular structure modification to extend a fused benzene ring at the perpendicular line C7=C8 of the planarization vibration axis of the originally Baird aromatic core , forming the PTBA molecule with electron delocalization and disturbed stability from the original Baird system (Figure ). PTBA showed sensitivity to temperature (Figure ), and when the temperature was lowered from 338K to 278K, the luminescence at 400nm and 550nm bands increased largely, the degree of emission enhancement at 400nm is considerably greater than that at 550nm, signifying that temperature and other factors constraining the bending-to-planar configuration flipping significantly impact the modulation of emission ratios among distinct luminescent centers. For photogenerated planarization behavior of Baird aromatic molecules, they proposed the kinetic sequence of excitation process: R*→ I*→P* (Figure ). The process entails progressing from the Franck-Condon state, passing through an intermediate state, and finally achieving a planarized core chromophore with enhanced delocalization of the π electrons. with permission. Copyright (2021), American Chemical Society. (e) Schematic representation of a quinolizine molecule, where the conjugated electrons in the two central six-membered rings collectively contribute to planarized conversion 8π electrons. (f) AIE curve of quinolizine. Reproduced from Ref. with permission.