Excited-State Double-Proton Transfer on 3-Methyl-7-azaindole in a Single Crystal:  Deuterium Isotope/Tunneling Effect

Yu, Wei-Shan; Cheng, Chung-Chih; Chang, Chih-Wei; Wu, Guan-Wei; Hsu, Chin-Hao; Chou, Pi‐Tai

doi:10.1021/jp020411x

Cited by 25 publications

(20 citation statements)

References 35 publications

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“…For example, Chou and co-workers successfully observed the excited-state double-proton transfer in single crystals of 7-azaindole derivatives, and investigated the tunneling reactions. 51,52 Sekikawa et al obtained a clear evidence of proton tunneling in crystalline salicylideneaniline and its derivatives by using femtosecond time-resolved fluorescence spectroscopy. 53,54 In these studies, the thermalization of the vibrational state of the enol form was observed.…”

Section: Introductionmentioning

confidence: 99%

Excited-state intramolecular proton transfer and charge transfer in 2-(2′-hydroxyphenyl)benzimidazole crystals studied by polymorphs-selected electronic spectroscopy

Konoshima

Nagao

Kiyota

et al. 2012

Phys. Chem. Chem. Phys.

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Crystal structures of polymorphs of 2-(2'-hydroxyphenyl)benzimidazole (HPBI), Forms α and β, are analyzed by X-ray crystallography. The fluorescence excitation (FE) and fluorescence spectra of the polymorphs are separately observed at temperatures 77-298 K. It has been found that the electronic spectra of the two crystal forms are significantly different from each other. Photo-excitation of the enol forms in Forms α and β induces the excited-state intramolecular proton transfer (ESIPT) to produce the S(1) state of the keto forms. In the FE spectra of Forms α and β, the S(1) ← S(0) (ππ*) transition of the keto form is observed in the 360-420 nm region in addition to that of the enol form in the 250-420 nm region. In the FE spectrum of Form β a new band peaking at 305 nm is observed, which is assigned to the S(1) ← S(0) transition of a non-planar enol form based on the observation of dual fluorescence in the UV and visible regions and quantum chemical calculation on the transition energy against the twisted angle between the benzimidazole and hydroxyphenyl rings. The fluorescence quantum yield (φ(T)) for the keto form is remarkably dependent on polymorphs at room temperature; φ(T) = 0.53 for Form α is much larger than φ(T) ≤ 0.23 for Form β. At 77 K the φ(T) values for Forms α and β increase to 0.67 and ≤0.57, respectively. The changes in the φ(T) values are associated with the intramolecular charge transfer (ICT) state. The potential barrier height between the S(1)-keto and S(1)-ICT states is significantly lower for Form β than for Form α. At 77 K the S(1)-keto → S(1)-ICT process followed by S(1)-ICT → S(0)-keto internal conversion is significantly suppressed in Form β. We compare difference in the dynamics between Forms α and β in the electronic ground and excited states.

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Section: Introductionmentioning

confidence: 99%

Excited-state intramolecular proton transfer and charge transfer in 2-(2′-hydroxyphenyl)benzimidazole crystals studied by polymorphs-selected electronic spectroscopy

Konoshima

Nagao

Kiyota

et al. 2012

Phys. Chem. Chem. Phys.

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“…The substitution of an electron-donating or an electron-withdrawing group in a CH hydrogen of the indole ring may change the strength of the intermolecular hydrogen bond and the ESDPT potential of (7AI) 2 . The ESDPT reaction in substituted (7AI) 2 dimers has been studied in the condensed phase by electronic spectroscopy, − but no report has been presented about the electronic spectra of the substituted (7AI) 2 dimers in the gas phase. Thus, we have investigated ESDPT in a 3-methyl-7-azaindole dimer (3MAI) 2 and its deuterated species.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, we have investigated ESDPT in a 3-methyl-7-azaindole dimer (3MAI) 2 and its deuterated species. Yu et al studied the ESDPT reaction in 3MAI in a single crystal . They remarked that 3MAI was a good model system to investigate ESDPT in a crystal, because ESDPT does not occur in a 7AI crystal because of the absence of the dual hydrogen-bonded structure.…”

Section: Introductionmentioning

confidence: 99%

Electronic Spectra of Jet-Cooled 3-Methyl-7-azaindole Dimer. Symmetry of the Lowest Excited Electronic State and Double-Proton Transfer

et al. 2004

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The fluorescence excitation spectra are recorded for jet-cooled dual hydrogen-bonded 3-methyl-7-azaindole dimer (3MAI)2-hh and deuterated dimers (3MAI)2-hd and (3MAI)2-dd near the electronic origin region of the S1−S0 transition, where hd and dd indicate the deuteration of an imino hydrogen and two imino hydrogens, respectively. A single origin is detected in the spectra of (3MAI)2-hh and (3MAI)2-dd, whereas two electronic origins separated by 13 cm-1 are detected in the spectrum of (3MAI)2-hd. The excited-state double-proton transfer (ESDPT) occurs in (3MAI)2-hh, while (3MAI)2-hd and (3MAI)2-dd undergo excited-state proton/deuteron transfer and excited-state double deuteron transfer, respectively. In (3MAI)2-hd, the excitation is localized on either the 3MAI-h or 3MAI-d moiety. The localization of the excitation is explained by a weak coupling of the excitonic states of (3MAI)2-hh and (3MAI)2-dd. The effective symmetry of the lowest excited state of (3MAI)2-hh and (3MAI)2-dd belongs to the C 2 h point group, while that of (3MAI)2-hd belongs to the C s point group. The vibronic patterns in the excitation spectra of the (3MAI)2 dimers is very similar to those of the 7-azaindole dimers, indicating that the methyl substitution provides little effect on the shape of the ESDPT potential.

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“…Generally, ESIPT reaction occurs between structurally and energetically asymmetric states and generates in the excited state a species with changed electronic and nuclear configuration, the tautomer “keto” form. The latter is isomeric to the initially excited normal (enol) form and demonstrates a fluorescence spectrum dramatically shifted to lower energies (longer wavelengths), up to 6000‐1000 cm −1 . And just because of these kinds of characteristics, lots of novel applications have been developed such as white emitting OLEDs, UV filters, optical chemosensors, molecular logic gates, UV absorbers, and so on …”

Section: Introductionmentioning

confidence: 99%

Unraveling photoexcitation dynamical behavior for bis (salicylidene)‐1,5‐diaminonaphthalene (BSD) system

Wang

Liu

Yang

2019

J of Physical Organic Chem

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In this work, a new excited state intramolecular proton transfer (ESIPT) mechanism of bis (salicylidene)-1,5-diaminonaphthalene (BSD) is proposed based on density functional theory (DFT) and time-dependent DFT methods. Given the intramolecular dual hydrogen bonds of BSD, we explore the excited state hydrogen bonding interactions for BSD and verify that the dual intramolecular hydrogen bonds of BSD molecule should be strengthened in the first excited state. Further, in the analyses about charge distribution upon excitation, we confirm that the charge redistribution around hydrogen bonding moieties plays important roles in enhancing dual hydrogen bonds and in facilitating ESIPT process. To reveal the detailed ESIPT mechanism, we construct the potential energy surfaces (PESs) in both S 0 and S 1 states along with hydrogen bonds. Via comparing potential energy barriers among the stable structures on the S 1 -state PES, we present the excited state intramolecular single proton transfer mechanism for BSD system. Moreover, the phenomenon and properties of fluorescence for BSD in experiment could be explained reasonably based on the ESIPT mechanism presented in this work. KEYWORDS charge redistribution, dual hydrogen bonds, electronic difference density, excited state intramolecular proton transfer, frontier molecular orbital

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Excited-State Double-Proton Transfer on 3-Methyl-7-azaindole in a Single Crystal: Deuterium Isotope/Tunneling Effect

Cited by 25 publications

References 35 publications

Excited-state intramolecular proton transfer and charge transfer in 2-(2′-hydroxyphenyl)benzimidazole crystals studied by polymorphs-selected electronic spectroscopy

Excited-state intramolecular proton transfer and charge transfer in 2-(2′-hydroxyphenyl)benzimidazole crystals studied by polymorphs-selected electronic spectroscopy

Electronic Spectra of Jet-Cooled 3-Methyl-7-azaindole Dimer. Symmetry of the Lowest Excited Electronic State and Double-Proton Transfer

Unraveling photoexcitation dynamical behavior for bis (salicylidene)‐1,5‐diaminonaphthalene (BSD) system

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