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A Novel Dialkylamino GFP Chromophore as an Environment-Polarity Sensor Reveals the Role of Twisted Intramolecular Charge Transfer. CHEMOSENSORS 2021. [DOI: 10.3390/chemosensors9080234] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We discovered a novel fluorophore by incorporating a dimethylamino group (–NMe2) into the conformationally locked green fluorescent protein (GFP) scaffold. It exhibited a marked solvent-polarity-dependent fluorogenic behavior and can potentially find broad applications as an environment-polarity sensor in vitro and in vivo. The ultrafast femtosecond transient absorption (fs-TA) spectroscopy in combination with quantum calculations revealed the presence of a twisted intramolecular charge transfer (TICT) state, which is formed by rotation of the –NMe2 group in the electronic excited state. In contrast to the bright fluorescent state (FS), the TICT state is dark and effectively quenches fluorescence upon formation. We employed a newly developed multivariable analysis approach to the FS lifetime in various solvents and showed that the FS → TICT reaction barrier is mainly modulated by H-bonding capability instead of viscosity of the solvent, accounting for the observed polarity dependence. These deep mechanistic insights are further corroborated by the dramatic loss of fluorogenicity for two similar GFP-derived chromophores in which the rotation of the –NMe2 group is inhibited by structural locking.
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Heo W, Joo T. Molecular Dynamics of Excited State Intramolecular Charge Transfer in Solution by Coherent Nuclear Wave Packets. Chemphyschem 2019; 20:1448-1455. [PMID: 30974028 DOI: 10.1002/cphc.201801103] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 04/11/2019] [Indexed: 11/09/2022]
Abstract
Revealing a proper reaction coordinate in a chemical reaction is the key step towards elucidation of the molecular reaction dynamics. In this report, we investigated the dynamics of intramolecular charge transfer (ICT) of 8-aminopyrene-1,3,6-trisulfonic acid (APTS) occurring in the excited state by time-resolved fluorescence (TF) and TF spectra. Accurate reaction rates and rate-dependent nuclear wave packets in the product state allow detailed investigation of the molecular reaction dynamics. The ICT rate is solvent dependent: (34 fs)-1 , (87 fs)-1 , and (∞)-1 in water, formamide, and dimethylformamide, respectively. By recording spectra of the nuclear wave packets for different reaction rates, chemical species responsible for the emission spectra can be positively identified. The origin of the wave packets can be deduced from the amplitude change of the wave packets at different reaction rates, and the vibrational modes that are associated with the reaction coordinate could be identified. Theoretical calculations of the vibrational reorganization energies reproduce the experimental spectrum of the nuclear wave packets and corroborate the conclusions.
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Affiliation(s)
- Wooseok Heo
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, South Korea
| | - Taiha Joo
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, South Korea
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3
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Temperature-dependence of spectral and photophysical properties of polycyclic aromatic hydrocarbon derivatives of acetylene and buta-1,3-diyne. J Photochem Photobiol A Chem 2018. [DOI: 10.1016/j.jphotochem.2018.03.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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4
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Variable-temperature absorption and emission properties of 1,2-diphenylacetylene and 1,4-diphenylbuta-1,3-diyne derivatives. J Photochem Photobiol A Chem 2017. [DOI: 10.1016/j.jphotochem.2017.08.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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5
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Zhang Y, Miao Y, Song X, Gao Y, Zhang Z, Ye K, Wang Y. Single-Molecule-based White-Light Emissive Organic Solids with Molecular-Packing-Dependent Thermally Activated Delayed Fluorescence. J Phys Chem Lett 2017; 8:4808-4813. [PMID: 28930465 DOI: 10.1021/acs.jpclett.7b02213] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
White-light-emitting single molecules have attracted broad attention because of their great potential for use in flat-panel displays and future light sources. We report a unique molecule of 3-(diphenylamino)-9H-xanthen-9-one (3-DPH-XO), which was found to exhibit bright white-light emission in the solid state caused by the spontaneous formation of a mixture with different polymorphs. Single-crystal analyses demonstrate that noncovalent interactions (such as π···π stacking, hydrogen bonding, and C-H···π interactions) induce different stacking arrangements (polymorphs A, B, and C) with different photophysical properties in a molecular solid. In addition, crystals B and C with the acceptor···acceptor stacking feature show the thermally activated delayed fluorescence (TADF) characteristics, indicating that appropriate noncovalent interactions could enhance the reverse intersystem crossing process and consequently lead to delayed fluorescence. This discovery provides an effective strategy for the design of new white-light-emitting single molecules as well as TADF materials.
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Affiliation(s)
- Yuewei Zhang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University , Changchun 130012, P. R. China
| | - Yang Miao
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University , Changchun 130012, P. R. China
| | - Xiaoxian Song
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University , Changchun 130012, P. R. China
| | - Yu Gao
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University , Changchun 130012, P. R. China
| | - Zuolun Zhang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University , Changchun 130012, P. R. China
| | - Kaiqi Ye
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University , Changchun 130012, P. R. China
| | - Yue Wang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University , Changchun 130012, P. R. China
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Du L, Lan Z. An On-the-Fly Surface-Hopping Program JADE for Nonadiabatic Molecular Dynamics of Polyatomic Systems: Implementation and Applications. J Chem Theory Comput 2016; 11:1360-74. [PMID: 26574348 DOI: 10.1021/ct501106d] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Nonadiabatic dynamics simulations have rapidly become an indispensable tool for understanding ultrafast photochemical processes in complex systems. Here, we present our recently developed on-the-fly nonadiabatic dynamics package, JADE, which allows researchers to perform nonadiabatic excited-state dynamics simulations of polyatomic systems at an all-atomic level. The nonadiabatic dynamics is based on Tully's surface-hopping approach. Currently, several electronic structure methods (CIS, TDHF, TDDFT(RPA/TDA), and ADC(2)) are supported, especially TDDFT, aiming at performing nonadiabatic dynamics on medium- to large-sized molecules. The JADE package has been interfaced with several quantum chemistry codes, including Turbomole, Gaussian, and Gamess (US). To consider environmental effects, the Langevin dynamics was introduced as an easy-to-use scheme into the standard surface-hopping dynamics. The JADE package is mainly written in Fortran for greater numerical performance and Python for flexible interface construction, with the intent of providing open-source, easy-to-use, well-modularized, and intuitive software in the field of simulations of photochemical and photophysical processes. To illustrate the possible applications of the JADE package, we present a few applications of excited-state dynamics for various polyatomic systems, such as the methaniminium cation, fullerene (C20), p-dimethylaminobenzonitrile (DMABN) and its primary amino derivative aminobenzonitrile (ABN), and 10-hydroxybenzo[h]quinoline (10-HBQ).
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Affiliation(s)
- Likai Du
- Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao, 266101 Shandong, People's Republic of China.,University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China.,The Qingdao Key Lab of Solar Energy Utilization and Energy Storage Technology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao, 266101 Shandong, People's Republic of China
| | - Zhenggang Lan
- Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao, 266101 Shandong, People's Republic of China.,University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China.,The Qingdao Key Lab of Solar Energy Utilization and Energy Storage Technology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao, 266101 Shandong, People's Republic of China
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7
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Catalán J, García MÁ, Claramunt RM. Influence of solvent basicity on DMABN photophysics. J PHYS ORG CHEM 2016. [DOI: 10.1002/poc.3613] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Javier Catalán
- Departamento de Química Física Aplicada; Universidad Autónoma de Madrid; Cantoblanco Madrid 28049 Spain
| | - M. Ángeles García
- Departamento de Química Orgánica y Bio-Orgánica; Facultad de Ciencias, UNED; Paseo Senda del Rey 9 Madrid 28040 Spain
| | - Rosa M. Claramunt
- Departamento de Química Orgánica y Bio-Orgánica; Facultad de Ciencias, UNED; Paseo Senda del Rey 9 Madrid 28040 Spain
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Park M, Im D, Rhee YH, Joo T. Coherent and Homogeneous Intramolecular Charge-Transfer Dynamics of 1-tert-Butyl-6-cyano-1,2,3,4-tetrahydroquinoline (NTC6), a Rigid Analogue of DMABN. J Phys Chem A 2014; 118:5125-34. [DOI: 10.1021/jp411227r] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Myeongkee Park
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea
| | - Donghong Im
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea
| | - Young Ho Rhee
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea
| | - Taiha Joo
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea
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Guo ZH, Jin ZX, Wang JY, Pei J. A donor–acceptor–donor conjugated molecule: twist intramolecular charge transfer and piezochromic luminescent properties. Chem Commun (Camb) 2014; 50:6088-90. [DOI: 10.1039/c3cc48980a] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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10
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Catalán J. On the dual emission of p-dimethylaminobenzonitrile and its photophysical implications. Phys Chem Chem Phys 2013; 15:8811-20. [PMID: 23639922 DOI: 10.1039/c3cp44627a] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A solvatochromic analysis of available absorption and LE and TICT emission data in p-dimethylaminobenzonitrile (DMABN) was conducted. Applying the Abe method to the results of a thermochromic analysis of DMABN in 1-chlorobutane (ClB) allowed us to determine the polarizability and dipole moment of the excited electronic states involved in the absorption and emission transitions. As shown herein, the LE → TICT excited state reaction for DMABN is triggered by the solvent polarity but is additionally influenced by the viscosity. The experimental evidence negates the assumption that the radiative constant for the TICT fluorescence of DMABN is temperature-dependent.
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Affiliation(s)
- Javier Catalán
- Departamento de Química Física Aplicada, Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain.
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12
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Pradhan T, Gazi HAR, Biswas R. Excited state intramolecular charge transfer reaction in nonaqueous electrolyte solutions: Temperature dependence. J Chem Phys 2009; 131:054507. [DOI: 10.1063/1.3196239] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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13
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Ríos Vázquez S, Ríos Rodríguez MC, Mosquera M, Rodríguez-Prieto F. Rotamerism, Tautomerism, and Excited-State Intramolecular Proton Transfer in 2-(4‘-N,N-Diethylamino-2‘-hydroxyphenyl)benzimidazoles: Novel Benzimidazoles Undergoing Excited-State Intramolecular Coupled Proton and Charge Transfer. J Phys Chem A 2007; 112:376-87. [DOI: 10.1021/jp076634a] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sonia Ríos Vázquez
- Departamento de Química Física, Facultade de Química, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
| | - M. Carmen Ríos Rodríguez
- Departamento de Química Física, Facultade de Química, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
| | - Manuel Mosquera
- Departamento de Química Física, Facultade de Química, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
| | - Flor Rodríguez-Prieto
- Departamento de Química Física, Facultade de Química, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
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Vázquez SR, Rodríguez MCR, Mosquera M, Rodríguez-Prieto F. Excited-State Intramolecular Proton Transfer in 2-(3‘-Hydroxy-2‘-pyridyl)benzoxazole. Evidence of Coupled Proton and Charge Transfer in the Excited State of Some o-Hydroxyarylbenzazoles. J Phys Chem A 2007; 111:1814-26. [PMID: 17309239 DOI: 10.1021/jp0653813] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The influence of solvent, temperature, and viscosity on the phototautomerization processes of a series of o-hydroxyarylbenzazoles was studied by means of ultraviolet-visible (UV-vis) absorption spectroscopy and steady-state and time-resolved fluorescence spectroscopy. The compounds studied were 2-(2'-hydroxyphenyl)benzimidazole (HBI), 2-(2'-hydroxyphenyl)benzoxazole (HBO), 2-(2'-hydroxyphenyl)benzothiazole (HBT), 2-(3'-hydroxy-2'-pyridyl)benzimidazole (HPyBI), and the new derivative 2-(3'-hydroxy-2'-pyridyl)benzoxazole (HPyBO), this one studied in neutral and acid media. All of these compounds undergo an excited-state intramolecular proton transfer (ESIPT) from the hydroxyl group to the benzazole N3 to yield an excited tautomer in syn conformation. A temperature- and viscosity-dependent radiationless deactivation of the tautomer has been detected for all compounds except HBI and HPyBI. We show that this radiationless decay also takes place for 2-(3-methyl-1,3-benzothiazol-3-ium-2-yl)benzenolate (NMeOBT), the N-methylated analog of the tautomer, whose ground-state structure has anti conformation. In ethanol, the radiationless decay shows intrinsic activation energy for HPyBO and HBO; however, it is barrierless for HBT and NMeOBT and controlled instead by the solvent dynamics. The relative efficiency of the radiationless decay in the series of molecules studied supports the hypothesis that this transition is connected with a charge-transfer process taking place in the tautomer, its efficiency being related to the strength of the electron donor (dissociated phenol or pyridinol moiety) and electron acceptor (protonated benzazole). We propose that the charge transfer is associated with a large-amplitude conformational change of the tautomer, the process leading to a nonfluorescent charge-transfer intermediate. The previous ESIPT step generates the structure with the suitable redox pair to undergo the charge-transfer process; therefore, an excited-state intramolecular coupled proton and charge transfer takes place for these compounds.
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Affiliation(s)
- Sonia Ríos Vázquez
- Departamento de Química Física, Facultade de Química, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
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16
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Oncul S, Demchenko AP. The effects of thermal quenching on the excited-state intramolecular proton transfer reaction in 3-hydroxyflavones. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2006; 65:179-83. [PMID: 16458048 DOI: 10.1016/j.saa.2005.10.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Revised: 07/19/2005] [Accepted: 10/06/2005] [Indexed: 05/06/2023]
Abstract
The 3-hydroxyflavone (3HF) and its derivatives are the classical objects in the studies of the mechanisms of excited-state intramolecular proton transfer (ESIPT) reaction due to very frequent observation of two separate bands in fluorescence emission belonging to reactant and reaction product. Those of them possessing electron-donor groups in 4' position find many applications as fluorescence sensors and probes because of their much higher sensitivity of their two-band ratiometric response to interactions with the environment. We report on the strong differences between 3HF and such derivatives in the behavior of their fluorescence spectra as a function of temperature. The thermal quenching changes the intensity ratio of two bands strongly for 3HF but does not change it for its studied derivatives. These results are interpreted in terms of different kinetic mechanisms of ESIPT reaction. In 3HF the equilibrium between the two excited-state species is not established prior to emission, so that the ESIPT reaction is under kinetic control, but in these derivatives the equilibrium is established faster than the emission and the reaction is under thermodynamic control. We suggest that the thermal perturbation of fluorescence spectra can be an extremely simple and convenient alternative to time-resolved spectroscopy for determining if slow irreversible or fast reversible ESIPT reaction gives rise to two bands of fluorescence spectra of similar magnitude. This is essential for the development of new wavelength-ratiometric fluorescence sensors and probes.
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Affiliation(s)
- Sule Oncul
- TUBITAK Research Institute for Genetic Engineering and Biotechnology, RIGEB, 41470 Gebze-Kocaeli, Turkey
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17
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Druzhinin SI, Ernsting NP, Kovalenko SA, Lustres LP, Senyushkina TA, Zachariasse KA. Dynamics of Ultrafast Intramolecular Charge Transfer with 4-(Dimethylamino)benzonitrile in Acetonitrile. J Phys Chem A 2005; 110:2955-69. [PMID: 16509618 DOI: 10.1021/jp054496o] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The kinetics of the intramolecular charge-transfer (ICT) reaction of 4-(dimethylamino)benzonitrile (DMABN) in the polar solvent acetonitrile (MeCN) is investigated by fluorescence quantum yield and picosecond time-correlated single photon counting (SPC) experiments over the temperature range from -45 to +75 degrees C, together with femtosecond Sn <-- S1 transient absorption measurements at room temperature. For DMABN in MeCN, the fluorescence from the locally excited (LE) state is strongly quenched, with an unquenched to quenched fluorescence quantum yield ratio of 290 at 25 degrees C. Under these conditions, even very small amounts of the photoproduct 4-(methylamino)benzonitrile (MABN) severely interfere, as the LE fluorescence of MABN is in the same spectral range as that of DMABN. The influence of photoproduct formation could be overcome by a simultaneous analysis of the picosecond and photostationary measurements, resulting in data for the activation barriers Ea (5 kJ/mol) and Ed (32 kJ/mol) of the forward and backward ICT reaction as well as the ICT reaction enthalpy and entropy: DeltaH (-27 kJ/mol) and DeltaS [-38 J/(mol K)]. The reaction hence takes place over a barrier, with double-exponential fluorescence decays, as to be expected in a two-state reaction. From femtosecond transient absorption down to 200 fs, the LE and ICT excited state absorption (ESA) spectra of DMABN in n-hexane (LE) and in MeCN (LE and ICT) and also of 4-aminobenzonitrile in MeCN (LE) are obtained. For DMABN in MeCN, the quenching of the LE and the rise of the ICT ESA bands occurs with a single characteristic time of 4.1 ps, the same as the ICT reaction time found from the picosecond SPC experiments at 25 degrees C. The sharp ICT peak at 320 nm does not change its spectral position after a pump-probe delay time of 200 fs, which suggests that large amplitude motions do not take place after this time. The increase with time in signal intensity observed for the LE spectrum of DMABN in n-hexane between 730 and 770 nm, is attributed to solvent cooling of the excess excitation energy and not to an inverse ICT --> LE reaction, as reported in the literature.
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Affiliation(s)
- Sergey I Druzhinin
- Max-Planck-Institut für biophysikalische Chemie, Spektroskopie und Photochemische Kinetik, 37070 Göttingen, Germany.
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Yoshihara T, Druzhinin SI, Demeter A, Kocher N, Stalke D, Zachariasse KA. Kinetics of Intramolecular Charge Transfer with N-Phenylpyrrole in Alkyl Cyanides. J Phys Chem A 2005; 109:1497-509. [PMID: 16833471 DOI: 10.1021/jp046586j] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
For the electron acceptor/donor molecule N-phenylpyrrole (PP), the fast intramolecular charge transfer (ICT) reaction accompanied by dual fluorescence from a locally excited (LE) and an ICT state is investigated in alkyl cyanide solvents as a function of temperature. After a comparison of the X-ray crystal structure of PP with calculations from the literature, absorption and fluorescence spectra of PP in a series of solvents over a wide polarity range are discussed. ICT with PP strongly depends on solvent polarity and starts to appear in solvents more polar than diethyl ether. From an analysis of the ICT/LE fluorescence quantum yield ratio Phi'(ICT)/Phi(LE), approximate data for the change in enthalpy -DeltaH of the ICT reaction of PP are obtained, ranging from 9 kJ/mol in acetonitrile (MeCN) to 4 kJ/mol in n-butyl cyanide (BuCN). From ICT and LE fluorescence decays of PP measured as a function of temperature, the forward (Ea = 9 kJ/mol in ethyl cyanide (EtCN) and 6 kJ/mol in MeCN) and backward (Ed = 16 kJ/mol in EtCN and MeCN) ICT reaction barriers are determined. From these data, -Delta H (7 kJ/mol (EtCN); 10 kJ/mol (MeCN)) is calculated, in good agreement with the results coming from Phi'(ICT)/Phi(LE). The data for Ea show that the forward ICT barrier becomes smaller with increasing solvent polarity, whereas the absence of change for Ed comes from the compensating increase of -DeltaH. Both observations are indicative of a late transition state for the LE --> ICT reaction. For PP in EtCN and MeCN, the ICT radiative rate constant k'(f)(ICT) increases with temperature. This is caused by the ICT low transition dipole moment and hence does not contain information on the molecular structure (twisted or planar) of the ICT state. The fast ICT observed with PP supports our previous conclusion, based on a comparison of PP with its planarized derivative fluorazene, that the pyrrole and phenyl moieties in the ICT state of PP are coplanar and possess substantial electronic coupling.
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Affiliation(s)
- Toshitada Yoshihara
- Max-Planck-Institut für biophysikalische Chemie, Spektroskopie und Photochemische Kinetik, 37070 Göttingen, Germany
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Dahl K, Biswas R, Ito N, Maroncelli M. Solvent Dependence of the Spectra and Kinetics of Excited-State Charge Transfer in Three (Alkylamino)benzonitriles. J Phys Chem B 2005; 109:1563-85. [PMID: 16851128 DOI: 10.1021/jp046605p] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Steady-state absorption and emission spectra and emission decay kinetics are reported for 4-aminobenzonitrile (ABN), 4-(1-azetidinyl)benzonitrile (P4C), 4-(1-pyrrolidinyl)benzonitrile (P5C), and 4-(1-piperidinyl)benzonitrile (P6C) in 24 room temperature solvents. In solvents of modest to high polarity, P4C, P5C, and P6C exhibit dual fluorescence and emission decays characteristic of the transformation from an initially prepared (LE) state to a more polar charge transfer (CT) state, whereas ABN does not undergo this reaction. The frequencies of the steady-state absorption and emission spectra of all of these solutes can be rationalized using a dielectric continuum description of the solvent and considering only the minima on the reactive surfaces, which are assumed to involve both an intramolecular (twisting) and a solvation coordinate. Characteristics of the gas-phase solutes deduced from this analysis are in good agreement with electronic structure calculations and indicate that differences in their spectra mainly reflect differences in the relative energies of the gas-phase LE and CT states. The relative yields of LE and CT emission are not described as satisfactorily by this model, and reasons for this failure are discussed. The kinetics of the LE --> CT reaction vary considerably with solute and solvent. In many solvents, the emission decays of P4C are reasonably described by a simple two-state kinetic scheme with time-independent rate constants. In P5C and P6C multiexponential decays are observed that reflect time-dependent shifts of the component spectra as well as time-dependent reaction rates. A simplified analysis of these complex dynamics provides estimates for both the free energy change Delta(r)G and (average) LE --> CT rate constant k(f) for a wide range of solute and solvent combinations. The driving force for reaction (-Delta(r)G) follows the order P6C > P5C > P4C and increases with increasing solvent polarity. The reaction rates are correlated to Delta(r)G and follow the opposite trend. The relationships observed between k(f) and Delta(r)G suggest that static solvent effects, i.e., barrier height changes, are the primary determinants of the solvent dependence in P4C. Correlations between barrier-corrected rates and solvation times suggest that dynamical solvent effects contribute substantially to the solvent dependence of the rates in P5C, and especially P6C.
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Affiliation(s)
- K Dahl
- Department of Chemistry, Penn State University, University Park, PA 16802, USA
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Belau L, Haas Y, Rettig W. Dual Emission of 4-(1H-Pyrrol-1-yl)benzonitrile Clusters with Acetonitrile in a Supersonic Jet and Its Absence in Phenylpyrrole Clusters. J Phys Chem A 2004. [DOI: 10.1021/jp037547v] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Leonid Belau
- Department of Physical Chemistry and the Farkas Center for Light Induced Processes, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Yehuda Haas
- Department of Physical Chemistry and the Farkas Center for Light Induced Processes, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Wolfgang Rettig
- Humboldt University of Berlin, Brook-Taylor-Str. 2, D-12489 Berlin, Germany
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Kauffman JF, Khajehpour M, Saleh N. Electron Transfer in a Flexible, Tethered Donor−Acceptor Pair: The Influence of Solute Conformation on Solvent-Dependent Free Energies. J Phys Chem A 2004. [DOI: 10.1021/jp035784s] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- John F. Kauffman
- Department of Chemistry, University of MissouriColumbia, Columbia, Missouri 65211
| | - Mazdak Khajehpour
- Department of Chemistry, University of MissouriColumbia, Columbia, Missouri 65211
| | - Na'il Saleh
- Department of Chemistry, University of MissouriColumbia, Columbia, Missouri 65211
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22
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Rappoport D, Furche F. Photoinduced Intramolecular Charge Transfer in 4-(Dimethyl)aminobenzonitrile − A Theoretical Perspective. J Am Chem Soc 2004; 126:1277-84. [PMID: 14746501 DOI: 10.1021/ja037806u] [Citation(s) in RCA: 198] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recent advances in time-dependent density functional theory (TDDFT) have led to computational methods that can predict properties of photoexcited molecules with satisfactory accuracy at comparably moderate cost. We apply these methods to study the photophysics and photochemistry of 4-(dimethyl)aminobenzonitrile (DMABN). DMABN is considered the paradigm of photoinduced intramolecular charge transfer (ICT), leading to dual fluorescence in polar solvents. By comparison of calculated emission energies, dipole moments, and vibrational frequencies with recent results from transient spectroscopy measurements, a definitive assignment of the electronic and geometric structure of the two lowest singlet excited states of DMABN is possible for the first time. We investigate the mechanism of the ICT reaction by means of minimum energy path calculations. The results confirm existing state-crossing models of dual fluorescence. Our study suggests that analytical TDDFT derivative methods will be useful to predict and classify emissive properties of other donor-acceptor systems as well.
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Affiliation(s)
- Dmitrij Rappoport
- Institut für Physikalische Chemie, Universität Karlsruhe, Kaiserstrasse 12, 76128 Karlsruhe, Germany
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23
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Grabowski ZR, Rotkiewicz K, Rettig W. Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures. Chem Rev 2003; 103:3899-4032. [PMID: 14531716 DOI: 10.1021/cr940745l] [Citation(s) in RCA: 2228] [Impact Index Per Article: 106.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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24
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Bothwell TG, Unruh JR, Johnson CK. Tyrosine and peptide reorientational mobility in polymer solutions: Time-dependent fluorescence anisotropy measurements. Biopolymers 2003; 69:351-62. [PMID: 12833262 DOI: 10.1002/bip.10363] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The ability of peptides to form biologically active conformations that bind to receptors is governed by their dynamics and their propensity to form stable structures. Such factors are consequently important in the design of peptide drugs. Moreover, the stability of such peptides depends on interactions of the peptide with the surrounding matrix. In this article, we study the effect of the polymer poly(vinyl pyrrolidone) (PVP) on the mobility and orientational dynamics of tyrosine and a model peptide, Val-Tyr-Pro-Asn-Gly-Ala (VYPNGA) in glycerol-water solutions. Orientational dynamics are studied experimentally by time-resolved fluorescence anisotropy decays of tyrosine. The presence of PVP leads to the possibility of a distribution of environments for the peptide. The orientational dynamics of tyrosine show that the probe molecule experiences two very different environments. In one, tyrosine rotational motion is weakly coupled to PVP, while in the other, tyrosine interacts strongly with PVP leading to much slower rotational times. The dynamics of VYPNGA are more complex. Fast intramolecular, localized reorientations of the tyrosine are detected. The temperature dependence of the reorientational dynamics of the tyrosine side chain reveal that these motions are shielded from solvent friction. In contrast, global motions of the peptide are severely restricted by PVP, suggesting the ability of the polymer to restrict peptide mobility.
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Affiliation(s)
- Troy G Bothwell
- Department of Chemistry, University of Kansas, Lawrence, KS 66045, USA
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25
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Pillai ZS, Sudeep PK, Thomas KG. Effect of viscosity on the singlet-excited state dynamics of some hemicyanine dyes. RESEARCH ON CHEMICAL INTERMEDIATES 2003. [DOI: 10.1163/156856703764929958] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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26
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Li R, Hageman MJ, Topp EM. Effect of viscosity on the deamidation rate of a model Asn-hexapeptide. THE JOURNAL OF PEPTIDE RESEARCH : OFFICIAL JOURNAL OF THE AMERICAN PEPTIDE SOCIETY 2002; 59:211-20. [PMID: 11966978 DOI: 10.1034/j.1399-3011.2002.00985.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The effect of viscosity on the deamidation rate of a model Asn-containing hexapeptide (l-Val-l-Tyr-Pro-l-Asn-Gly-l-Ala) was assessed in aqueous solution and in solids containing varying amounts of poly(vinyl pyrrolidone) (PVP) and water. Stability studies were conducted at 0.1 mg/mL peptide and 0-50% PVP (w/w) in aqueous solution, and at 5% (w/w) peptide and different relative humidities (31.6, 53.1, 74.4 and 96%) in the solid state. The parent peptide and its deamidation products were analysed by reverse-phase high-performance liquid chromatography. Deamidation rates decreased with increasing solvent viscosity in a manner described by a semi-empirical mathematical model developed to describe this relationship. The results suggest that the motion of the Asn side-chain along the reaction coordinate is a function of the macroscopic solvent viscosity. However, the apparent energy barrier for the diffusive movement of the side-chain appears to be less than the energy barrier for that associated with macroscopic viscosity. The dependence of the deamidation rate on viscosity in both viscous solution and hydrated solids further demonstrates the importance of mobility in peptide deamidation.
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Affiliation(s)
- R Li
- Department of Pharmaceutical Chemistry, The University of Kansas, Lawrence, KS 66047, USA
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27
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Fuss W, Pushpa KK, Rettig W, Schmid WE, Trushin SA. Ultrafast charge transfer via a conical intersection in dimethylaminobenzonitrile. Photochem Photobiol Sci 2002; 1:255-62. [PMID: 12661965 DOI: 10.1039/b111678a] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The L(a)-like S2 state (2A) of 4-(dimethylamino)benzonitrile was pumped at 267 nm in the gas phase at 130 degrees C. Nonresonant multiphoton ionization at 800 nm with mass-selective detection then probed the subsequent processes. Whereas ionization at the Franck-Condon geometry only gave rise to the parent ion, fragmentation increased on motion towards the charge-transfer (CT) state. This useful difference is ascribed to a geometry-dependent resonance in the ion. The time constants found are interpreted by ultrafast (approximately 68 fs) relaxation through a conical intersection to both the CT and the L(b)-type S1 state (1B). Then the population equilibrates between these two states within 1 ps. From there the molecule relaxes within 90 ps to a lower excited state which can only be a triplet state (T(n)) and then decomposes within 300 ps. Previous experiments either investigated only 1B --> CT relaxation-which does not take place in the gas phase or nonpolar solvents for energetic reasons--or, starting from S2 excitation, typically had insufficient time resolution (>1 ps) to detect the temporary charge transfer. Only recently temporary population of the CT state was found in a nonpolar solvent (Kwok et al., J. Phys. Chem. A. 2000, 104, 4188), a result fully consistent with our mechanism. We also show that S2 --> S1 relaxation does not occur vertically but involves an intermediate strong geometrical distortion, passing through a conical intersection.
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Affiliation(s)
- Werner Fuss
- Max-Planck-Institut für Quantenoptik, D-85741 Garching, Germany.
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28
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Maus M, Rettig W. The Excited State Equilibrium between Two Rotational Conformers of a Sterically Restricted Donor−Acceptor Biphenyl As Characterized by Global Fluorescence Decay Analysis. J Phys Chem A 2001. [DOI: 10.1021/jp012432h] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Michael Maus
- W. Nernst-Institut für Physikalische und Theoretische Chemie, Humboldt-Universität zu Berlin, Bunsenstrasse 1, D-10117 Berlin, Germany
| | - Wolfgang Rettig
- W. Nernst-Institut für Physikalische und Theoretische Chemie, Humboldt-Universität zu Berlin, Bunsenstrasse 1, D-10117 Berlin, Germany
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29
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From Cyanines to Styryl Bases — Photophysical Properties, Photochemical Mechanisms, and Cation Sensing Abilities of Charged and Neutral Polymethinic Dyes. ACTA ACUST UNITED AC 2001. [DOI: 10.1007/978-3-642-56853-4_7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
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30
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Gude C, Rettig W. Radiative and Nonradiative Excited State Relaxation Channels in Squaric Acid Derivatives Bearing Differently Sized Donor Substituents: A Comparison of Experiment and Theory. J Phys Chem A 2000. [DOI: 10.1021/jp000139w] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Claudia Gude
- Institut für Chemie, Physikalische und Theoretische Chemie, Humboldt-Universität zu Berlin, Bunsenstrasse 1, D-10117 Berlin, Germany
| | - Wolfgang Rettig
- Institut für Chemie, Physikalische und Theoretische Chemie, Humboldt-Universität zu Berlin, Bunsenstrasse 1, D-10117 Berlin, Germany
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31
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Rettig W, Zietz B. Do twisting and pyramidalization contribute to the reaction coordinate of charge-transfer formation in DMABN and derivatives? Chem Phys Lett 2000. [DOI: 10.1016/s0009-2614(99)01323-8] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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32
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Strehmel B, Strehmel V, Younes M. Fluorescence probes for investigation of epoxy systems and monitoring of crosslinking processes. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1099-0488(19990701)37:13<1367::aid-polb3>3.0.co;2-k] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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33
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Sczepan M, Rettig W, L. Bricks Y, Slominski YL, Tolmachev AI. Unsymmetric cyanines: chemical rigidization and photophysical properties. J Photochem Photobiol A Chem 1999. [DOI: 10.1016/s1010-6030(99)00045-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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34
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Maus M, Rettig W, Bonafoux D, Lapouyade R. Photoinduced Intramolecular Charge Transfer in a Series of Differently Twisted Donor−Acceptor Biphenyls As Revealed by Fluorescence. J Phys Chem A 1999. [DOI: 10.1021/jp9905023] [Citation(s) in RCA: 214] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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