Unraveling the Mechanism for Tuning the Fluorescence of Fluorescein Derivatives: The Role of the Conical Intersection and nπ* State

Abstract

Although a large number of fluorescein derivatives have been developed and applied in many different fields, the general mechanisms for tuning the fluorescence of fluorescein derivatives still remain uncovered. Herein, we found that the fluorescence quenching of neutral form of fluorescein derivatives in acidic medium resulted from a dark nπ* state, whereas the fluorescence of the anionic form of fluorescein derivatives in the gas phase and alkaline solutions was tuned by minimal energy conical intersection (MECI). The formation of MECI involved significant rotation of benzene ring and flip-flop motion of xanthene moiety, which would be restricted by intermolecular hydrogen bonding and lowering temperature. The energy barrier for reaching MECI depended on the substituents in the benzene moiety in accordance with experimentally observed substituent effects. These unprecedented mechanisms would lead to a recognition of fluorescein derivatives and could provide a correct and instructive design strategy for further developing new fluorescein derivatives.

The sensing mechanism of fluorescent probe for PhSH and the process of ESIPT

“…Moreover, the dihedral angle between FL and Q group has been changed obviously. As previous studies [60,61], the large geometry change between S 0 and S 1 states may lead to a fast internal conversion and thereby quenching the fluorescence. Thus, the fluorescent quenching mechanism of FQ-DNP is TICT.…”

Solvent-polarity-dependent conformation and ESIPT behaviors for 2-(benzimidazol-2-yl)-3-hydroxychromone: a novel dynamical mechanism

“…39 In particular, the excited-state behaviors and related photochemical as well as photophysical properties of target molecules could be changed by the solvent polarity. [40][41][42][43][44][45][46] Thus, in this work, we mainly focused on exploring the excited-state dynamical process and relative ESIPT mechanism for BI3HC in organic solvents with different polarities. Briefly, our simulated results present a novel dynamical mechanism for the BI3HC fluorophore that differs from previous attributions and conclusions.…”

Theoretical Study on the Atom-Substituted Quinazoline Derivatives with Faint Emission as Potential Sunscreens

“…In addition, it can be found that the energy barriers of reverse ground-state intramolecular proton transfer (RGSIPT) of HQ, HQS, and HQSe are far lower than the energy barriers of ground-state intramolecular proton transfer (GSIPT) and ESIPT. − Thus, it can be found that the three compounds can quickly return to the enol form in the S 0 state, and it is favorable to enhance the effective acting time of sunscreen.…”