1
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Sánchez F, Gutiérrez M, Douhal A. Taking Advantage of a Luminescent ESIPT-Based Zr-MOF for Fluorochromic Detection of Multiple External Stimuli: Acid and Base Vapors, Mechanical Compression, and Temperature. ACS APPLIED MATERIALS & INTERFACES 2023; 15:56587-56599. [PMID: 37983009 DOI: 10.1021/acsami.3c14348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2023]
Abstract
Luminescent materials responsive to external stimuli have captivated great attention owing to their potential implementation in noninvasive photonic sensors. Luminescent metal-organic frameworks (LMOFs), a type of porous crystalline material, have emerged as one of the most promising candidates for these applications. Moreover, LMOFs constructed with organic linkers that undergo excited-state intramolecular proton-transfer (ESIPT) reactions are particularly relevant since changes in the surrounding environment induce modifications in their emission properties. Herein, an ESIPT-based LMOF, UiO-66-(OH)2, has been synthesized, spectroscopically and photodynamically characterized, and tested for detecting multiple external stimuli. First, the spectroscopic and photodynamic characterization of the organic linker (2,5-dihydroxyterephthalic acid (DHT)) and the UiO-66-(OH)2 MOF demonstrates that the emission properties are mainly governed by the enol → keto tautomerization, occurring in the organic linker via the ESIPT reaction. Afterward, the UiO-66-(OH)2 MOF proves for the first time to be a promising candidate to detect vapors of acid (HCl) and base (Et3N) toxic chemicals, changes in the mechanical compression (exercised pressure), and changes in the temperature. These results shed light on the potential of ESIPT-based LMOFs to be implemented in the development of advanced optical materials and luminescent sensors.
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Affiliation(s)
- Francisco Sánchez
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, S/N, 45071 Toledo, Spain
| | - Mario Gutiérrez
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, S/N, 45071 Toledo, Spain
| | - Abderrazzak Douhal
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, S/N, 45071 Toledo, Spain
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2
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de la Hoz Tomás M, Yamaguchi M, Cohen B, Hisaki I, Douhal A. Deciphering the ultrafast dynamics of a new tetraphenylethylene derivative in solutions: charge separation, phenyl ring rotation and CC bond twisting. Phys Chem Chem Phys 2023; 25:1755-1767. [PMID: 36594826 DOI: 10.1039/d2cp05220b] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Tetraphenylethylene (TPE) derivatives are one of the fundamental units for developing aggregation induced emission (AIE) scaffolds. However, the underlying mechanisms implicated in the relaxation of the excited TPE remain a topic of ongoing discussion, while the effect of bulky substituents on its photobehaviour is still under scrutiny. Here, we report a detailed study of the photophysical properties of a new symmetrical and bulky TPE derivative with terphenyl groups (TTECOOBu) in solvents of different polarities and viscosities. Using femto- to nanosecond (fs-ns) time-resolved absorption and emission techniques, we elucidated the role of the phenyl group rotations and core ethylene bond twisting in its behaviour. We demonstrate that TTECOOBu in DCM solutions undergoes a 600 fs charge separation along the ethylene bond leading to a resonance structure with a lifetime of ∼1 ns. The latter relaxes via two consecutive events: a twisting of the ethylene bond (∼ 9 ps) and a rotation of the phenyl rings (∼ 30 ps) leading to conformationally-relaxed species with a largely Stokes-shifted emission (∼ 12 500 cm-1). The formation of the red-emitting species clearly depends on the solvent viscosity and rigidity of the medium. Contrary to the photobehavior in the highly viscous triacetin or rigid polymer matrix of PMMA, a reversible mechanism was observed in DCM and DMF solutions. These results provide new findings on the ultrafast mechanisms of excited TPE derivatives and should help in the development of new molecular rotors with interesting AIE properties for photonic applications.
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Affiliation(s)
- Mario de la Hoz Tomás
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, S/N, 45071 Toledo, Spain.
| | - Mao Yamaguchi
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
| | - Boiko Cohen
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, S/N, 45071 Toledo, Spain.
| | - Ichiro Hisaki
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
| | - Abderrazzak Douhal
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, S/N, 45071 Toledo, Spain.
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3
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Li C, Hu B, Cao Y, Li Y. Unveiling the dehydrogenation mechanism of dihydrogen‐bonded phenol‐borane‐dimethylamine complex in the ground and excited states. J PHYS ORG CHEM 2022. [DOI: 10.1002/poc.4415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Chaozheng Li
- School of Mechanical and Electrical Engineering Henan Institute of Science and Technology Xinxiang China
| | - Bo Hu
- School of Mechanical and Electrical Engineering Henan Institute of Science and Technology Xinxiang China
| | - Yonghua Cao
- School of Mechanical and Electrical Engineering Henan Institute of Science and Technology Xinxiang China
| | - Yongfeng Li
- School of Mechanical and Electrical Engineering Henan Institute of Science and Technology Xinxiang China
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4
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Gutiérrez M, García E, Monterde C, Sánchez F, Douhal A. Modulating the spectroscopy and dynamics of a proton-transfer dye by functionalizing with phenyl groups. Phys Chem Chem Phys 2022; 24:6828-6835. [PMID: 35244633 DOI: 10.1039/d1cp05294b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Molecules undergoing excited-state proton transfer (ESPT) reactions are among the most interesting systems from spectroscopic and photophysical viewpoints. These molecules can be further functionalized with electron donating or accepting groups, inducing intramolecular charge transfer (ICT) events, which might be coupled to the ESIPT ones, conferring them with different spectroscopic and photophysical properties, which can be essential to implement the related materials in many key scientific and technological fields. Here, we report new benzimidazole derivatives that are functionalized with a phenyl group, 2-(5,10-diphenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenol (DP-HPPI), and its methylated equivalent, 2-(2-methoxyphenyl)-5,10-diphenyl-1H-phenanthro[9,10-d]imidazole (DP-MPPI). The results prove that these molecules in solutions undergo an ultrafast ICT (400-700 fs) reaction. Additionally, DP-HPPI also undergoes a reversible ESIPT process in dichloromethane. However, this is precluded in acetonitrile due to the involvement of intermolecular H-bonds in this solvent. These results provide key insights into the development of proton-transfer materials with bespoke spectral and photodynamical properties.
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Affiliation(s)
- Mario Gutiérrez
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, S. N., 45071 Toledo, Spain.
| | - Eduardo García
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, S. N., 45071 Toledo, Spain.
| | - Cristina Monterde
- Instituto de Química Orgánica General, IQOG-CSIC, Juan de la Cierva, 3, 28006 Madrid, Spain
| | - Félix Sánchez
- Instituto de Química Orgánica General, IQOG-CSIC, Juan de la Cierva, 3, 28006 Madrid, Spain
| | - Abderrazzak Douhal
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, S. N., 45071 Toledo, Spain.
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Femto- to Millisecond Time-Resolved Photodynamics of a Double-Functionalized Push-Pull Organic Linker: Potential Candidate for Optoelectronically Active MOFs. Int J Mol Sci 2020; 21:ijms21124366. [PMID: 32575438 PMCID: PMC7352538 DOI: 10.3390/ijms21124366] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 06/11/2020] [Accepted: 06/16/2020] [Indexed: 12/25/2022] Open
Abstract
The design of improved organic linkers for the further engineering of smarter metal–organic framework (MOF) materials has become a paramount task for a wide number of material scientists. In this report, a luminescent double-functionalized push–pull (electron donor–acceptor) archetype organic molecule, dimethyl 4-amino-8-cyanonaphthalene-2,6-dicarboxylate (Me2CANADC), has been synthesized and characterized. The optical steady-state properties of Me2CANADC are strongly influenced by the surrounding environment as a direct consequence of its strong charge transfer (CT) character. The relaxation from its first electronically excited singlet state follows a double pathway: (1) on one side deactivating from its local excited (LE) state in the sub-picosecond or picosecond time domain, and (2) on the other side undergoing an ultrafast intramolecular charge transfer (ICT) reaction that is slowing down in viscous solvents. The deactivation to the ground state of these species with CT character is the origin of the Me2CANADC luminescence, and they present solvent-dependent lifetime values ranging from 8 to 18 ns. The slow photodynamics of Me2CANADC unveils the coexistence of a non-emissive triplet excited state and the formation of a long-lived charge separated state (2 µs). These observations highlight the promising optical properties of Me2CANADC linker, opening a window for the design of new functional MOFs with huge potential to be applied in the fields of luminescent sensing and optoelectronics.
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Wiethaus G, Toldo JM, da Silveira Santos F, da Costa Duarte R, Gonçalves PFB, Rodembusch FS. Experimental and theoretical investigation of long-wavelength fluorescence emission in push–pull benzazoles: intramolecular proton transfer or charge transfer in the excited state? Phys Chem Chem Phys 2019; 21:4408-4420. [DOI: 10.1039/c8cp05186k] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
ESIPT is disfavoured and charge-transfer emission, prior to ESIPT, seems to be responsible for long-emission wavelengths.
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Affiliation(s)
- Guilherme Wiethaus
- Grupo de Pesquisa em Fotoquímica Orgânica Aplicada
- Universidade Federal do Rio Grande do Sul – Instituto de Química
- Porto Alegre-RS
- Brazil
| | - Josene Maria Toldo
- Grupo de Química Teórica e Computacional
- Universidade Federal do Rio Grande do Sul – Instituto de Química
- Porto Alegre-RS
- Brazil
| | - Fabiano da Silveira Santos
- Grupo de Pesquisa em Fotoquímica Orgânica Aplicada
- Universidade Federal do Rio Grande do Sul – Instituto de Química
- Porto Alegre-RS
- Brazil
| | - Rodrigo da Costa Duarte
- Grupo de Pesquisa em Fotoquímica Orgânica Aplicada
- Universidade Federal do Rio Grande do Sul – Instituto de Química
- Porto Alegre-RS
- Brazil
| | - Paulo Fernando Bruno Gonçalves
- Grupo de Química Teórica e Computacional
- Universidade Federal do Rio Grande do Sul – Instituto de Química
- Porto Alegre-RS
- Brazil
| | - Fabiano Severo Rodembusch
- Grupo de Pesquisa em Fotoquímica Orgânica Aplicada
- Universidade Federal do Rio Grande do Sul – Instituto de Química
- Porto Alegre-RS
- Brazil
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7
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Gomez E, Alarcos N, Monterde C, Sánchez F, Moreno M, Douhal A. Experimental and theoretical insights into the influence of electronic density on proton-transfer reactions. Phys Chem Chem Phys 2018; 20:27149-27161. [PMID: 30334550 DOI: 10.1039/c8cp03185a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report on the excited-state behavior of proton-transfer phenanthroimidazole derivatives, such as HPPI and NMHPPI, in solutions using steady-state and femto- to nanosecond time-resolved fluorescence spectroscopies. Experimental observations are supported by theoretical calculations (TDDFT). In dichloromethane (DCM) and acetonitrile (ACN), two different paths are found for the excited-state intramolecular proton-transfer (ESIPT) reactions following two different channels. A fast and direct channel (ESIPT1) in 1-2.5 ps and a slower one (ESIPT2) in 12-15 ps, the latter being more influenced by the solvent viscosity (30 ps for HPPI and 20 ps for NMHPPI in triacetin (TAC) solutions). The slowing down of the ESIPT2 reaction is explained in terms of an intramolecular charge transfer (ICT) reaction coupled to a twisting motion to reach a more suitable conformation of the involved parts in the proton-transfer motion. The absence of OH/OD exchange effects in the ultrafast and slow proton-transfer dynamics suggests that the ESIPT reactions, which involve intramolecular and solvent coordinates, do not occur via tunneling. These results reveal new insights into the photobehavior of proton-transfer dyes, which might help in designing photosensors or lighting devices.
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Affiliation(s)
- Eduardo Gomez
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, S.N., 45071 Toledo, Spain.
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8
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Du C, Zhou Q, Zhang M, Song P, Ma F. Excited-state intramolecular proton transfer of 6-amino-2-(2′-hydroxyphenyl) benzoxazole (6A-HBO) in different solvents. J PHYS ORG CHEM 2018. [DOI: 10.1002/poc.3901] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Can Du
- Department of Physics; Liaoning University; Shenyang China
| | - Qiao Zhou
- Department of Physics; Liaoning University; Shenyang China
| | - Meixia Zhang
- Department of Physics; Liaoning University; Shenyang China
| | - Peng Song
- Department of Physics; Liaoning University; Shenyang China
- Liaoning Key Laboratory of Semiconductor Light Emitting and Photocatalytic Materials; Liaoning University; Shenyang China
| | - Fengcai Ma
- Department of Physics; Liaoning University; Shenyang China
- Liaoning Key Laboratory of Semiconductor Light Emitting and Photocatalytic Materials; Liaoning University; Shenyang China
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9
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Mohbiya DR, Sekar N. Tuning ‘Stokes Shift’ and ICT Character by Varying the Donor Group in Imidazo[1,5 a]pyridines: A Combined Optical, DFT, TD-DFT and NLO Approach. ChemistrySelect 2018. [DOI: 10.1002/slct.201702579] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Dhanraj R. Mohbiya
- Dyestuff Technology Department; Institute of Chemical Technology; Nathalal Parekh Marg, Matunga Mumbai 400019 India
| | - Nagaiyan Sekar
- Dyestuff Technology Department; Institute of Chemical Technology; Nathalal Parekh Marg, Matunga Mumbai 400019 India
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10
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Alarcos N, Cohen B, Ziółek M, Douhal A. Photochemistry and Photophysics in Silica-Based Materials: Ultrafast and Single Molecule Spectroscopy Observation. Chem Rev 2017; 117:13639-13720. [PMID: 29068670 DOI: 10.1021/acs.chemrev.7b00422] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Silica-based materials (SBMs) are widely used in catalysis, photonics, and drug delivery. Their pores and cavities act as hosts of diverse guests ranging from classical dyes to drugs and quantum dots, allowing changes in the photochemical behavior of the confined guests. The heterogeneity of the guest populations as well as the confinement provided by these hosts affect the behavior of the formed hybrid materials. As a consequence, the observed reaction dynamics becomes significantly different and complex. Studying their photobehavior requires advanced laser-based spectroscopy and microscopy techniques as well as computational methods. Thanks to the development of ultrafast (spectroscopy and imaging) tools, we are witnessing an increasing interest of the scientific community to explore the intimate photobehavior of these composites. Here, we review the recent theoretical and ultrafast experimental studies of their photodynamics and discuss the results in comparison to those in homogeneous media. The discussion of the confined dynamics includes solvation and intra- and intermolecular proton-, electron-, and energy transfer events of the guest within the SBMs. Several examples of applications in photocatalysis, (photo)sensors, photonics, photovoltaics, and drug delivery demonstrate the vast potential of the SBMs in modern science and technology.
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Affiliation(s)
- Noemí Alarcos
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha , Avenida Carlos III, S.N., 45071 Toledo, Spain
| | - Boiko Cohen
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha , Avenida Carlos III, S.N., 45071 Toledo, Spain
| | - Marcin Ziółek
- Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University , Umultowska 85, 61-614 Poznań, Poland
| | - Abderrazzak Douhal
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha , Avenida Carlos III, S.N., 45071 Toledo, Spain
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11
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Li Y, Chu TS. DFT/TDDFT Study on the Sensing Mechanism of a Fluorescent Probe for Hydrogen Sulfide: Excited State Intramolecular Proton Transfer Coupled Twisted Intramolecular Charge Transfer. J Phys Chem A 2017. [DOI: 10.1021/acs.jpca.7b02606] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Yang Li
- State Key Laboratory
of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Tian-Shu Chu
- State Key Laboratory
of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P. R. China
- Institute for Computational Sciences and
Engineering, Laboratory of New Fiber Material and Modern Textile,
the Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071, P. R. China
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12
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Substituent Modulation from ESIPT to ICT Emission in Benzoimidazolphenyl-methanones Derivatives: Synthesis, Photophysical and DFT Study. J SOLUTION CHEM 2017. [DOI: 10.1007/s10953-017-0602-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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13
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Kumpulainen T, Lang B, Rosspeintner A, Vauthey E. Ultrafast Elementary Photochemical Processes of Organic Molecules in Liquid Solution. Chem Rev 2016; 117:10826-10939. [DOI: 10.1021/acs.chemrev.6b00491] [Citation(s) in RCA: 249] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Tatu Kumpulainen
- Department of Physical Chemistry,
Sciences II, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Bernhard Lang
- Department of Physical Chemistry,
Sciences II, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Arnulf Rosspeintner
- Department of Physical Chemistry,
Sciences II, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Eric Vauthey
- Department of Physical Chemistry,
Sciences II, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
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14
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The Effect of Substituent Position on Excited State Intramolecular Proton Transfer in Benzoxazinone Derivatives: Experiment and DFT Calculation. J Fluoresc 2016; 27:235-242. [DOI: 10.1007/s10895-016-1950-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2016] [Accepted: 10/03/2016] [Indexed: 11/26/2022]
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15
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Azarias C, Budzák Š, Laurent AD, Ulrich G, Jacquemin D. Tuning ESIPT fluorophores into dual emitters. Chem Sci 2016; 7:3763-3774. [PMID: 29997864 PMCID: PMC6008603 DOI: 10.1039/c5sc04826e] [Citation(s) in RCA: 118] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 02/23/2016] [Indexed: 12/24/2022] Open
Abstract
Using first-principle approaches, we show how ESIPT can be controlled by fine-tuning of substituents, hence leading to new dual emitters.
Dyes undergoing excited-state intramolecular proton transfer (ESIPT) are known to present large Stokes shifts as a result of the important geometrical reorganisation following photon absorption. When the ESIPT process is not quantitative, one can obtain dual emitters characterised by two distinct fluorescence bands, observed due to emissions from both the canonical and ESIPT isomers. However, dual emission generally requires to maintain a very specific balance, as the relative excited-state free energies of the two tautomers have to be within a narrow window to observe the phenomenon. Consequently, simple chemical intuition is insufficient to optimise dual emission. In the present contribution, we investigate, with the help of quantum-mechanical tools and more precisely, time-dependent density functional theory (TD-DFT) and algebraic diagrammatic construction (ADC), a wide panel of possible ESIPT/dual emitters with various substituents. The selected protocol is first shown to be very robust on a series of structures with known experimental behaviour, and next is applied to novel derivatives with various substituents located at different positions. This work encompasses the largest chemical library of potential ESIPT compounds studied to date. We pinpoint the most promising combinations for building dual emitters, highlight unexpected combination effects and rationalise the impact of the different auxochromes.
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Affiliation(s)
- Cloé Azarias
- CEISAM , UMR CNRS 6230 , Université de Nantes , BP 92208, 2, Rue de la Houssinière , 44322 Nantes, Cedex 3 , France . ; Tel: +33-2-51-12-55-64
| | - Šimon Budzák
- CEISAM , UMR CNRS 6230 , Université de Nantes , BP 92208, 2, Rue de la Houssinière , 44322 Nantes, Cedex 3 , France . ; Tel: +33-2-51-12-55-64
| | - Adèle D Laurent
- CEISAM , UMR CNRS 6230 , Université de Nantes , BP 92208, 2, Rue de la Houssinière , 44322 Nantes, Cedex 3 , France . ; Tel: +33-2-51-12-55-64
| | - Gilles Ulrich
- Institut de Chimie et Procédés pour l'Energie , l'Environnement et la Santé (ICPEES) UMR7515 CNRS Université de Strasbourg , 25 rue Becquerel , 67087 Strasbourg Cedex 02 , France
| | - Denis Jacquemin
- CEISAM , UMR CNRS 6230 , Université de Nantes , BP 92208, 2, Rue de la Houssinière , 44322 Nantes, Cedex 3 , France . ; Tel: +33-2-51-12-55-64.,Institut Universitaire de France , 1, rue Descartes , F-75005 Paris Cedex 05 , France
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16
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Alarcos N, Gutiérrez M, Liras M, Sánchez F, Moreno M, Douhal A. Direct observation of breaking of the intramolecular H-bond, and slowing down of the proton motion and tuning its mechanism in an HBO derivative. Phys Chem Chem Phys 2016; 17:14569-81. [PMID: 25966780 DOI: 10.1039/c5cp01437a] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We report on spectroscopic and photodynamical behaviours of 5-amino-2-(2'-hydroxyphenyl)benzoxazole (5A-HBO) in different solutions. The dye undergoes an ultrafast ICT reaction (<50 fs) (comparable to that observed for its methylated derivative, 5A-MBO), in agreement with the results of TD-DFT theoretical calculations (gas phase). Depending on the used solvent, the ICT reaction can be followed by a reversible/irreversible excited-state intramolecular proton transfer (ESIPT) reaction or by breaking of the intramolecular hydrogen bond (IHB). 5A-HBO in n-heptane solution exhibits an irreversible and slow (20 ps) ESIPT reaction, while that of the parent compound, HBO, takes place in less than 150 fs. Compared to excited HBO behaviour, theoretical calculations on 5A-HBO suggest a higher energy barrier (∼4 kcal mol(-1)) between the relaxed enol and keto tautomers, in addition to a less stabilization of the latter, which is in agreement with experiments in n-heptane. On the other hand, in dichloromethane, after the ICT reaction a subsequent and reversible proton motion occurs in an extraordinary slower regime (ns-time scale). No isotopic effect (OH/OD exchange) was observed in this solvent reflecting that the reversible ESIPT reaction evolves along the IHB and solvent coordinates. Using tetrahydrofurane and acetonitrile, we observed a breaking of the IHB due to specific intermolecular interactions with solvent molecules. This leads to the formation of open-enol forms, which undergo an ICT reaction as it occurs in 5A-MBO. These results bring new findings in the coupled ICT and ESIPT reactions. The photobehaviour of this new dye remarkably changes with the solvent nature, opening up the window for further research and possible applications in sensing polarity or H-bonding of media similar to that of the biological ones.
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Affiliation(s)
- Noemí Alarcos
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, S.N., 45071 Toledo, Spain.
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17
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Alarcos N, Gutiérrez M, Liras M, Sánchez F, Douhal A. From intra- to inter-molecular hydrogen bonds with the surroundings: steady-state and time-resolved behaviours. Photochem Photobiol Sci 2015; 14:1306-18. [PMID: 26066612 DOI: 10.1039/c5pp00079c] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report on the photodynamics of 2-(2'-hydroxyphenyl)benzoxazole (HBO), compared to its amino derivatives, 6-amino-2-(2'-hydroxypheny)benzoxazole (6A-HBO) and 5-amino-2-(2'-hydroxypheny)benzoxazole (5A-HBO) in N,N-dimethylformamide (DMF) solutions. HBO at S0 shows a reversible deprotonation reaction leading to the production of anionic forms. However, for 6A-HBO and 5A-HBO, DMF containing KOH is necessary to produce the anions. Excited HBO in DMF exhibits intra- as well as inter-molecular proton transfer (ESIPT and ESPT) reactions. With excitation at 330 nm, we observed the open-enol, anti-enol and keto forms with different emission and lifetimes (620 ps, 1.5 ns, and 74 ps, respectively), while with the excitation at 433 nm, only the anionic species emission was detected (3.7 ns). Contrary to HBO, 6A-HBO and 5A-HBO do not exhibit any proton transfer process, and only the emissions of the open-enol charge-transferred forms (open-ECT) were observed, which are comparable to those of their methylated derivatives (6A-MBO and 5A-MBO). Femtosecond studies of 6A-MBO and 6A-HBO in DMF indicate that an intramolecular charge-transfer (ICT) reaction (∼80 fs) and solvent relaxation process (2 ps) take place at S1. Remarkably, the photoinduced breaking of the intramolecular hydrogen bond of 6A-HBO and the formation of an intermolecular hydrogen bond with DMF molecules occurs in 80 ps, while for 5A-HBO, this process occurs in less than 10 ps. In this study, we have demonstrated that the presence and position of the amino group in the HBO framework change both the S0 and S1 behaviours of the intramolecular H-bonds; a result which might be useful for the design and better understanding of supramolecular systems based on intra- and intermolecular H-bonds.
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Affiliation(s)
- Noemí Alarcos
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, S.N., 45071 Toledo, Spain.
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Alarcos N, Gutierrez M, Liras M, Sánchez F, Douhal A. An abnormally slow proton transfer reaction in a simple HBO derivative due to ultrafast intramolecular-charge transfer events. Phys Chem Chem Phys 2015; 17:16257-69. [PMID: 25870162 DOI: 10.1039/c5cp00577a] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We report on the steady-state, picosecond and femtosecond time-resolved studies of a charge and proton transfer dye 6-amino-2-(2'-hydroxyphenyl)benzoxazole (6A-HBO) and its methylated derivative 6-amino-2-(2'-methoxyphenyl)benzoxazole (6A-MBO), in different solvents. With femtosecond resolution and comparison with the photobehaviour of 6A-MBO, we demonstrate for 6A-HBO in solution, the photoproduction of an intramolecular charge-transfer (ICT) process at S1 taking place in ∼140 fs or shorter, followed by solvent relaxation in the charge transferred species. The generated structure (syn-enol charge transfer conformer) experiences an excited-state intramolecular proton-transfer (ESIPT) reaction to produce a keto-type tautomer. This subsequent proton motion occurs in 1.2 ps (n-heptane), 14 ps (DCM) and 35 ps (MeOH). In MeOH, it is assisted by the solvent molecules and occurs through tunneling for which we got a large kinetic isotope effect (KIE) of about 13. For the 6A-DBO (deuterated sample in CD3OD) the global proton-transfer reaction takes place in 200 ps, showing a remarkable slow KIE regime. The slow ESIPT reaction in DCM (14 ps), not through tunnelling as it is not sensitive to OH/OD exchange, has however to overcome an energy barrier using intramolecular as well as solvent coordinates. The rich ESIPT dynamics of 6A-HBO in the used solutions is governed by an ICT reaction, triggered by the amino group, and it is solvent dependent. Thus, the charge injection to a 6A-HBO molecular frame makes the ICT species more stable, and the phenol group less acidic, slowing down the subsequent ESIPT reaction. Our findings bring new insights into the coupling between ICT and ESIPT reactions on the potential-energy surfaces of several barriers.
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Affiliation(s)
- Noemí Alarcos
- Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, S.N., 45071 Toledo, Spain.
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