Reaction Mechanism of Photodeamination Induced by Excited-State Intramolecular Proton Transfer of the Anthrol Molecule

Abstract

The photodeamination reaction of the anthrol molecule generating the high-activity quinone methide intermediate has been investigated ( J. Org. Chem. 2017 , 82 , 6006 - 6021 ), though lacking careful explanation for its reaction mechanism. In our research, the mechanism of the anthrol molecule photodeamination induced by excited-state intramolecular proton transfer was reported for the first time. Absorption and emission spectra calculated for the work presented here agreed well with experimental results. To propose a molecular-level explanation of the photodeamination reaction, we calculated bond parameters, corresponding infrared vibrational frequencies, Mayer bond orders, and visualized frontier molecular orbitals of different molecules, and the hydrogen bond strengthening behavior in excited states was confirmed, enhancing the excited state intramolecular proton transfer of the anthrol molecule. Moreover, we concluded that photoisomerization weakened the bond strength between nitrogen and carbon atoms, which promoted the photodeamination reaction. Finally, for visually and quantificationally revealing the photodeamination mechanism, we have established the three-dimensional potential energy surfaces for the deamination reaction in different electronic states and calculated the corresponding reaction Gibbs free energies, it can be confirmed that the photodeamination reaction of the anthrol molecule must be induced by a proton transfer reaction in the excited state.

Aggregation Promotes Excited-State Intramolecular Proton Transfer for Benzothiazole-Substituted Tetraphenylethylene Compound

“…Given the paramount importance of excited-state relaxation and dynamics in photophysical and photochemical processes, ESIPT is highly attractive because of its large Stokes shift, dual emission, low self-quenching fluorescence, and high quantum efficiency. − It has been confirmed to be one of the most elementary processes in photosystem II, biological protein, DNA, and ribonucleic acid. − Generally, the ESIPT could be an ultrafast reaction, which undergoes the following four-level reaction cycle: absorption → ESIPT → dual emission → reversed ground-state PT. Endowed with these unique characteristics, ESIPT compounds exhibit potential applications in wide fields such as molecular logic gates, fluorescence sensors, photostabilizers, cell images, and so forth. − Organic fluorescence ESIPT-based chromophores have attracted more and more attention in the field of optoelectronic devices because of their highly sensitive and peculiar photophysical properties. ESIPT coupled to AIEE could produce devices with emission across the visible spectrum, which facilitates this kind of compounds possessing the potential to contribute to the design of more efficient highly emissive ESIPT materials.…”

A theoretical investigation on the excited state intramolecular single or double proton transfer mechanism of a salicyladazine system

“…And, this kind of shift in the steady‐state absorption and emission spectra determines whether the ESIPT reaction occurs in the experimental phenomenon. It cannot be denied that the energy barrier of the ESIPT reaction might be affected by pH, solute properties, and the surrounding interactions with other solute molecules, and so on . Thus, determining the potential energy barrier for the ESIPT process is crucial under different conditions.…”

The alkoxylation effects on the excited‐state intramolecular proton transfer behaviors for 2,6‐bis(benzothiazolyl‐2‐yl)phenol fluorophore: A theoretical research

“…It could lead to various photo-physical and photo-biological behaviors, such as intramolecular or intermolecular charge transfer (ICT), fluorescence resonance energy transfer (FRET), excitedstate intramolecular or intermolecular proton transfer (ESIPT), and photo-induced electron transfer (PET). [16][17][18][19][20][21][22][23][24][25] As far as we know, one of the most challenging cases in photochemical field is the investigation of excited-state hydrogen bonding interactions in molecules due to both proton acceptor and donor moieties. [26][27][28][29][30] Accordingly, excited-state dynamical processes of hydrogen bonding molecules should be usually complicated by the fact that multiple equilibriums and various species can appear in excited states.…”

“…In effect, to the best of our knowledge, only spectroscopic techniques including electronic spectra and time‐resolved spectra could just provide the indirect information about photochemical properties. [ 16–38 ] In addition, relevant researches about the alkoxylation effects on ESIPT reactions are also limited in both experimental and theoretical fields. In this work, therefore, we mainly focus on exploring the effects for ESIPT behaviors bringing from the alkoxylation of the 4‐position of DBTP fluorophore.…”

“…It could lead to various photo‐physical and photo‐biological behaviors, such as intramolecular or intermolecular charge transfer (ICT), fluorescence resonance energy transfer (FRET), excited‐state intramolecular or intermolecular proton transfer (ESIPT), and photo‐induced electron transfer (PET). [ 16–25 ]…”