Vibrational-Gated Intersystem Crossing in Phenolphthalein Dianion: A TDDFT Insight into the Fluorescence Quenching Mechanism.
The structural rigidity of molecular frameworks plays a pivotal role in modulating intersystem crossings (ISCs). Here, we systematically investigate the distinct fluorescence behaviors of the phenolphthalein dianion (PHP2-) and the fluorescein dianion (FLU2-)─two structurally analogous xanthene derivatives. By employin...