Theoretical Insights Into the Excited State Double Proton Transfer Mechanism of Deep Red Pigment Alkannin

Given the tremendous potential applications of excited state intramolecular proton transfer (ESIPT) systems, ESIPT molecules have received widespread attention. In this work, based on density functional theory (DFT) and time‐dependent DFT (TDDFT) methods, we theoretically study the excited state dynamical behaviors of salicyladazine (SA) molecules. Our simulated results show that the double intramolecular hydrogen bonds of SA are strengthened in the S1 state via exploring bond distances, bond angles, and infrared (IR) vibrational spectra. Exploring the frontier molecular orbitals (MOs), we confirm that charge redistributions indeed have effects on excited state dynamical behaviors. The increased electronic densities on N atoms and the decreased electronic densities on O atoms imply that charge redistribution may trigger the ESPT process. Analyzing the constructed S0‐state and S1‐state potential energy surfaces (PESs), we confirm that only the excited state single proton transfer reaction can occur although SA possesses two intramolecular hydrogen bonds. In this work, we clarify the specific ESIPT mechanism, which may facilitate developing novel applications based on the SA system in future.

Section: Introductionmentioning

confidence: 99%

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

Zhang

Zhao

Cheng

et al. 2019

“…In addition, for further revealing the effects of the fluoride‐triggered Si‐O bond cleavage process on the fluoride‐sensing mechanism of the BIPA sensor, we theoretically simulate the desilylation process via constructing the potential energy curve (Figure ). The reason why we adopt this procedure is that the theoretical potential energy curve should be a good way to deal with the investigations of fluorescence sensors . Thus for the BIPA system, the potential energy curve is constructed via shortening the Si‐F bond distance coupling with fixing Si‐F length from 4.00 to 1.30 Å within the step of 0.10 Å in the ground state.…”

Section: Resultsmentioning

confidence: 99%

Theoretical insights into the fluoride anion response mechanism of a fluorescence chemosensor 4‐((tert‐butyldiphenylsilyl)oxy)isophthalaldehyde

Yang

Gao

et al. 2019

It is well known that ions play important roles in our life sciences, and the detection of ions has attracted more and more attention. In this work, we focus on the sensing response mechanism of a novel fluoride chemosensor, 4‐((tert‐butyldiphenylsilyl)oxy)isophthalaldehyde (BIPA). Based on density functional theory and time‐dependent density functional theory methods, we clarify that fluoride anions could trigger the cleavage reaction of the Si‐O bond of BIPA in the ground state. And, the potential energy curve of desilylation process reveals the rapid response to fluoride anions. Comparing the binding energies between fluoride anions and other anions, we confirm that only the fluoride anions could be detected using the BIPA chemosensor in ethanol solvent. Considering the photo‐excitation process, we find the strong intramolecular charge transfer process for the S0 → S1 transition could explain the red shift of the absorption spectra of the BIPA system. This work not only clarifies the specific fluoride‐sensing mechanism, but also plays a role in facilitating designing and synthesizing of novel fluorescent sensors in future.

“…And one thing should be mentioned that the fluorescence peak of enol* exhibits the normal Stokes shift, while the keto* form shows the longer emission peak. Generally, this kind of significant Stokes shift can be as large as 6,000–12,000 cm −1 …”

Section: Introductionmentioning

confidence: 99%

Insights into the excited state intramolecular proton transfer process and mechanism of the novel 3‐hydroxythioflavone system: A theoretical study

Wang

Zhao

et al. 2019

Self Cite

It is well known that the molecular excited state dynamical process plays important roles in designing and developing novel applications. In this work, based on density functional theory and time‐dependent density functional theory methods, we theoretically explored a novel 3‐hydroxythioflavone (3HTF). Through calculating the electrostatic potential surface of the 3HTF structure, we confirm the formation of intramolecular hydrogen bonding O2‐H3···O4. Our theoretically obtained dominating bond lengths and bond angles involved in hydrogen bonds demonstrate that the intramolecular hydrogen bonds should be strengthened in the S1 state. Coupling with the simulated infrared vibrational spectra, we further verify the enhanced hydrogen bonding O2‐H3···O4 in the S1 state. Upon photoexcitation, we found that the charge transfer characteristics around hydrogen bonding moieties play important roles in facilitating the excited state intramolecular proton transfer (ESIPT) process. Via constructing potential energy curves in both S0 and S1 states, we confirm the almost nonbarrier ESIPT reaction should be an ultrafast process that further explains the previous experimental phenomenon. At last, we search the S1‐state transition state (TS) structure along with ESIPT path, based on which we simulate the intrinsic reaction coordinate path that further confirms the ESIPT mechanism. We hope that our theoretical work could guide novel applications based on the 3HTF system in future.