Excited-State Proton Transfer Mechanism of 2,6-Diazaindoles·(H2O)n (n = 2–4) Clusters

Tang, Zhe; Qi, Yutai; Wang, Yi; Zhou, Panwang; Tian, Jing; Fei, Xu

doi:10.1021/acs.jpcb.7b10207

Cited by 58 publications

(36 citation statements)

References 63 publications

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“…For example, when new ESPT chromophores are developed, the design strategies and possible mechanisms are proposed based on the experimental results. − However, the suggested mechanism is usually not completely corrected and sometimes problematic, thereby requiring further theoretical studies to validate or invalidate; − this can provide guidance for developing new ESPT chromophores . When multiple protons are involved, such as in excited-state double PT (ESDPT), whether the mechanism is stepwise or concerted is usually under debate among experimental scientists; , extensive theoretical studies are necessary to resolve this controversy. − When solvent molecules participate in ESPT as proton acceptor or catalyst, the size of the solute·(solvent) n cluster is difficult to determine experimentally, and theoretical studies are necessary. − …”

Section: Introductionmentioning

confidence: 99%

Unraveling the Detailed Mechanism of Excited-State Proton Transfer

2018

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As one of the most fundamental processes, excited-state proton transfer (ESPT) plays a major role in both chemical and biological systems. In the past several decades, experimental and theoretical studies on ESPT systems have attracted considerable attention because of their tremendous potential in fluorescent probes, biological imaging, white-light-emitting materials, and organic optoelectronic materials. ESPT is related to fluorescence properties and usually occurs on an ultrafast time scale at or below 100 fs. Consequently, steady-state and femtosecond time-resolved absorption, fluorescence, and vibrational spectra have been used to explore the mechanism of ESPT. However, based on previous experimental studies, direct information, such as transition state geometries, energy barrier, and potential energy surface (PES) of the ESPT reaction, is difficult to obtain. These data are important for unravelling the detailed mechanism of ESPT reaction and can be obtained from state-of-the-art ab initio excited-state calculations. In recent years, an increasing number of experimental and theoretical studies on the detailed mechanism of ESPT systems have led to tremendous progress. This Account presents the recent advances in theoretical studies, mainly those from our group. We focus on the cases where the theoretical studies are of great importance and indispensable, such as resolving the debate on the stepwise and concerted mechanism of excited-state double proton transfer (ESDPT), revealing the sensing mechanism of ESPT chemosensors, illustrating the effect of intermolecular hydrogen bonding on the excited-state intramolecular proton transfer (ESIPT) reaction, investigating the fluorescence quenching mechanism of ESPT systems by twisting process, and determining the size of the solute·(solvent) n cluster for the solvent-assisted ESPT reaction. Through calculation of vertical excitation energies, optimization of excited-state geometries, and construction of PES of the ESPT reactions, we provide modifications to experimentally proposed mechanisms or completely new mechanism. Our proposed new and inspirational mechanisms based on theoretical studies can successfully explain the previous experimental results; some of the mechanisms have been further confirmed by experimental studies and provided guidance for researchers to design new ESPT chemosensors. Determination of the energy barrier from an accurate PES is the key to explore the ESPT mechanism with theoretical methods. This approach becomes complicated when the charge transfer state is involved for time-dependent density functional theory (TDDFT) method and optimally tuned range-separated TDDFT provides an alternative way. To unveil the driving force of ESPT reaction, the excited-state molecular dynamics combined with the intrinsic reaction coordinate calculations can be employed. These advanced approaches should be used for further studies on ESPT systems.

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Section: Introductionmentioning

confidence: 99%

Unraveling the Detailed Mechanism of Excited-State Proton Transfer

2018

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“…Controlling the various factors of ESIPT molecules would contribute to develop new multiemissive materials. ESIPT dynamics have been deeply investigated theoretically and experimentally [31][32][33][34][35][36][37][38][39][40][41][42]. Takagi et al [37] studied the ESIPT fluorescence properties of methoxy-substituted 2-hydroxyphenylbenzimidazole.…”

Section: Introductionmentioning

confidence: 99%

Theoretical investigations on forward–backward ESIPT processes of three fluorophores deriving from 2-(2′-hydroxyphenyl)thiazole

Liang

Fang

2021

Photochem Photobiol Sci

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The photophysical properties and excited-state intramolecular proton transfer (ESIPT) processes for 2-(2′-hydroxyphenyl)-4-chloromethylthiazole (1), 2-(2′-hydroxyphenyl)-4-phenylthiazole (2), 2-(2′-hydroxyphenyl)-4-hydroxymethyl-thiazole (3) were studied at the TD-B3PW91/6-31 + G(d, p)/IEFPCM level. The structures of 1-3 were fully optimized and the corresponding structural parameters, infrared spectra and electron densities in the ground (S 0 ) and the first excited (S 1 ) states were analyzed. The calculated absorption and fluorescence wavelengths of 1-3 reproduced the experimental data. The potential energy curves of the S 0 and S 1 states were built and the ESIPT processes were clarified. Our results showed that the intramolecular H-bonds of 3 and 2 in the S 1 state were the strongest and the weakest, respectively, and then the ESIPT potential barriers of 3 and 2 were the lowest and highest, respectively. Among the three phenol-thiazole type probes, the compound 2 with phenyl ring group at the 4 position of the thiazole ring had the larger π-conjugation, and had the higher ESIPT potential barrier at the same time. The corresponding compound 1 and 3 with CH 2 Cl and CH 2 OH had the lower ESIPT barrier.

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“…Although time‐dependent density functional theory (TDDFT) has become the most wide‐spread ab initio model to explore the electronically excited state properties of medium and large molecules due to its balance between computational efficiency and accuracy of results, using this model to deal with biradicals and conical intersections where double excitations play significant roles is difficult . TDDFT with certain conventional approximate functional typically underestimates the excitation energies of charge transfer (CT) states, and range‐separated (RS) functionals can be used as alternatives .…”

Section: Introductionmentioning

confidence: 99%

Why the lowest electronic excitations of rhodamines are overestimated by time‐dependent density functional theory

Zhou

2018

Int J of Quantum Chemistry

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Rhodamines are widely used as laser dyes and fluorescent probes due to their excellent photophysical and photochemical properties. Previous theoretical studies have shown that the lowest excitation energies of rhodamines are overestimated systematically by time‐dependent density functional theory (TDDFT). In this study, we first perform a TDDFT benchmark study with 21 exchange‐correlation functionals (XCFs) on a series of rhodamines and assess the performance of different types of functional in predicting the lowest excitation energies of rhodamines. Statistical results reveal that the fraction of Hartree–Fock exchange (HFX) included in the XCF is a key parameter. Pure functionals without HFX offer the best performance, with the mean absolute error (MAE) of approximately 0.1 eV. However, they provide a wrong order of the lowest nπ* and ππ* states and suffer from charge‐transfer contamination problem for rhodamine dyes (RDs) in zwitterionic form. Among the other tested functionals, popular global hybrid functional B3LYP delivers the smallest MAE of 0.36 eV. We then perform calculations with second‐order algebraic diagrammatic construction and extended multiconfiguration quasi‐degenerate perturbation theory at second‐order of PT expansion methods. Remarkably accurate results are obtained. We confirm that the reason for the overestimation of the lowest excitation energies of RDs by TDDFT method should be similar to that of cyanine dyes, and that double excitations contribute to this systematic deviation.

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Excited-State Proton Transfer Mechanism of 2,6-Diazaindoles·(H₂O)_n (n = 2–4) Clusters

Cited by 58 publications

References 63 publications

Unraveling the Detailed Mechanism of Excited-State Proton Transfer

Unraveling the Detailed Mechanism of Excited-State Proton Transfer

Theoretical investigations on forward–backward ESIPT processes of three fluorophores deriving from 2-(2′-hydroxyphenyl)thiazole

Why the lowest electronic excitations of rhodamines are overestimated by time‐dependent density functional theory

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