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Dobrowolski JC, Karpińska G. Substituent Effect in the First Excited Triplet State of Monosubstituted Benzenes. ACS OMEGA 2020; 5:9477-9490. [PMID: 32363300 PMCID: PMC7191863 DOI: 10.1021/acsomega.0c00712] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 03/16/2020] [Indexed: 05/08/2023]
Abstract
The structure of 30 monosubstituted benzenes in the first excited triplet T1 state was optimized with both unrestricted (U) and restricted open shell (RO) approximations combined with the ωB97XD/aug-cc-pVTZ basis method. The substituents exhibited diverse σ- and π-electron-donating and/or -withdrawing groups. Two different positions of the substituents are observed in the studied compounds in the T1 state: one distorted from the plane and the other coplanar with a quinoidal ring. The majority of the substituents are π-electron donating in the first group while π-electron withdrawing in the second one. Basically, U- and RO-ωB97XD approximations yield concordant results except for the B-substituents and a few of the planar groups. In the T1 state, the studied molecules are not aromatic, yet aromaticity estimated using the HOMA (harmonic oscillator model of aromaticity) index increases from ca. -0.2 to ca. 0.4 with substituent distortion, while in the S1 state, they are only slightly less aromatic than in the ground state (HOMA ≈0.8 vs ≈1.0, respectively). Unexpectedly, the sEDA(T1) and pEDA(T1) substituent effect descriptors do not correlate with analogous parameters for the ground and first excited singlet states. This is because in the T1 state, the geometry of the ring changes dramatically and the sEDA(T1) and pEDA(T1) descriptors do not characterize only the functional group but the entire molecule. Thus, they cannot provide useful scales for the substituents in the T1 states. We found that the spin density in the T1 states is accumulated at the Cipso and Cp atoms, and with the substituent deformation angle, it nonlinearly increases at the former while decreases at the latter. It appeared that the gap between singly unoccupied molecular orbital and singly occupied molecular orbital (SUMO-SOMO) is determined by the change of the SOMO energy because the former is essentially constant. For the nonplanar structures, SOMO correlates with the torsion angle of the substituent and the ground-state pEDA(S0) descriptor of the π-electron-donating substituents ranging from 0.02 to 0.2 e. Finally, shapes of the SOMO-1 instead of SOMO frontier orbitals in the T1 state somehow resemble the highest occupied molecular orbital ones of the S0 and S1 states. For several planar systems, the shape of the U- and RO-density functional theory-calculated SOMO-1 orbitals differs substantially.
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2
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Dobrowolski JC, Lipiński PFJ, Karpińska G. Substituent Effect in the First Excited Singlet State of Monosubstituted Benzenes. J Phys Chem A 2018; 122:4609-4621. [PMID: 29698609 DOI: 10.1021/acs.jpca.8b02209] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
sEDA, pEDA, and cSAR descriptors of the substituent effect were determined for >30 monosubstituted benzenes in the first excited singlet S1 state at the LC-ωB97XD/aug-cc-pVTZ level. It was found that in the S1 state, the σ- and π-valence electrons are a bit less and a bit more affected, respectively, than in the S0 state, but basically, the effect in both states remains the same. In the S0 and S1 states, the d(C-X) distances to the substituent's first atom and the ring perimeter correlate with the sEDA and pEDA in the appropriate states, respectively. The energies and the gap of the frontier orbitals in the two states are linearly correlated and for the HOMO(S1), LUMO(S1), and HOMO(S1)-LUMO(S1) gap correlate also with the pEDA(S1) and cSAR(S1) descriptors. In all studied correlations, three similar groups of substituents can be distinguished, for which correlations (i) are very good, (ii) deviate slightly, and (iii) deviate significantly. Comparison of the shape of the HOMO(S0) and HOMO(S1) orbitals shows that for case (i) HOMO orbitals exhibit almost perfect antisymmetry against the benzene plane, for case (ii) the antisymmetry of HOMO in one of the states is either perturbed or changed, and for case (iii) one HOMO state has σ-character.
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Affiliation(s)
- Jan Cz Dobrowolski
- Department for Medicines Biotechnology and Bioinformatics , National Medicines Institute , 30/34 Chełmska Street , 00-725 Warsaw , Poland
| | - Piotr F J Lipiński
- Department of Neuropeptides , Mossakowski Medical Research Centre PAS , 5 Pawińskiego Street , 02-106 Warsaw , Poland
| | - Grażyna Karpińska
- Department for Medicines Biotechnology and Bioinformatics , National Medicines Institute , 30/34 Chełmska Street , 00-725 Warsaw , Poland
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Ashwood B, Ortiz-Rodríguez LA, Crespo-Hernández CE. Photochemical relaxation pathways of S 6-methylthioinosine and O 6-methylguanosine in solution. Faraday Discuss 2018; 207:351-374. [PMID: 29372193 DOI: 10.1039/c7fd00193b] [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
S6-Methylthioinosine and O6-methylguanosine are byproducts resulting from the enzymatic reactions of sulfur-substituted prodrugs in cells and from the interaction of alkylating agents with cellular DNA, respectively. Their photochemistry has not been investigated, and it is currently unknown whether light absorption by these byproducts may pose any threat to the cell. In this contribution, their photoinduced processes upon absorption of UVB radiation are reported using broadband transient absorption spectroscopy. Plausible electronic relaxation mechanisms are proposed for both biological molecules, which are supported by steady-state absorption and emission measurements, and by singlet and triplet vertical excitation energies performed on a large subset of ground-state optimized conformational isomers in solution. The results are compared to the body of knowledge gathered in the scientific literature about the light-induced processes in the sulfur-substituted and canonical purine monomers. In particular, it is shown that S6-methylation decreases the rate to populate the lowest-energy triplet state and blueshifts the ground-state absorption spectrum compared to those for the sulfur-substituted prodrugs and for the 6-thioguanosine metabolite. Similarly, O6-methylation decreases the rate of internal conversion to the ground state observed in the guanine monomers by more than 10-fold in acetonitrile and 40-fold in aqueous solution, while it redshifts the ground-state absorption spectrum. Collectively, this investigation provides relevant new insights about the relationship between structural modifications of the purine chromophore and the electronic relaxation mechanisms in this important group of biological molecules.
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Affiliation(s)
- Brennan Ashwood
- Department of Chemistry, Center for Chemical Dynamics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, USA.
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4
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Peng XL, Migani A, Li QS, Li ZS, Blancafort L. Theoretical study of non-Hammett vs. Hammett behaviour in the thermolysis and photolysis of arylchlorodiazirines. Phys Chem Chem Phys 2018; 20:1181-1188. [DOI: 10.1039/c7cp07281c] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Calculations show that the different Hammett behaviour of arylchlorodiazirines is due to different mechanisms in the ground and excited state.
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Affiliation(s)
- Xing-Liang Peng
- Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials
- Key Laboratory of Cluster Science of Ministry of Education
- School of Chemistry and Chemical Engineering
- Beijing Institute of Technology
- 100081 Beijing
| | - Annapaola Migani
- Departament de Química Biològica i Modelització Molecular
- IQAC-CSIC
- Jordi Girona 18-26
- 08034 Barcelona
- Spain
| | - Quan-Song Li
- Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials
- Key Laboratory of Cluster Science of Ministry of Education
- School of Chemistry and Chemical Engineering
- Beijing Institute of Technology
- 100081 Beijing
| | - Ze-Sheng Li
- Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials
- Key Laboratory of Cluster Science of Ministry of Education
- School of Chemistry and Chemical Engineering
- Beijing Institute of Technology
- 100081 Beijing
| | - Lluís Blancafort
- Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona
- Facultat de Ciències
- C/M. A. Capmany 69
- 17003 Girona
- Spain
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5
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Brister MM, Piñero-Santiago LE, Morel M, Arce R, Crespo-Hernández CE. Photochemical Relaxation Pathways in Dinitropyrene Isomer Pollutants. J Phys Chem A 2017; 121:8197-8206. [PMID: 28984454 DOI: 10.1021/acs.jpca.7b04769] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Dinitropyrenes are polycyclic aromatic pollutants prevalent in the environment. While their transformations by sunlight in the environment have been documented, the effect that the nitro-group substitution pattern has on the relaxation pathways has not been extensively studied. In this contribution, the steady-state and femtosecond-to-microsecond excited-state dynamics of 1,3-dinitropyrene and 1,8-dinitropyrene isomers are investigated upon visible light excitation at 425 nm and compared with those recently reported for the 1,6-dinitropyrene isomer. The experimental results are complemented with ground- and excited-state density functional calculations. It is shown that excitation at 425 nm results in the ultrafast branching of the excited-state population in the S1 state to populate the triplet state in ca. 90% yield and to form a nitropyrenoxy radical in less than 10% yield. In addition, the position of the NO2 group does not affect significantly the excited-state relaxation mechanism, while it does influence the absorption and fluorescence spectra, the fluorescence, triplet, singlet oxygen, and photodegradation yields, as well as the relative yield of radical formation. Radical formation is implicated in the photodegradation of these pollutants, while in the presence of hydrogen donors, direct reactions from the triplet state are also observed.
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Affiliation(s)
- Matthew M Brister
- Department of Chemistry, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Luis E Piñero-Santiago
- Department of Chemistry, University of Puerto Rico , Río Piedras Campus, San Juan, Puerto Rico 00931, United States
| | - María Morel
- Department of Chemistry, University of Puerto Rico , Río Piedras Campus, San Juan, Puerto Rico 00931, United States
| | - Rafael Arce
- Department of Chemistry, University of Puerto Rico , Río Piedras Campus, San Juan, Puerto Rico 00931, United States
| | - Carlos E Crespo-Hernández
- Department of Chemistry, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
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6
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Pollum M, Ashwood B, Jockusch S, Lam M, Crespo-Hernández CE. Unintended Consequences of Expanding the Genetic Alphabet. J Am Chem Soc 2016; 138:11457-60. [DOI: 10.1021/jacs.6b06822] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Marvin Pollum
- Department
of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Brennan Ashwood
- Department
of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Steffen Jockusch
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
| | - Minh Lam
- Department
of Dermatology, Case Western Reserve School of Medicine, Cleveland, Ohio 44106, United States
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7
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Vendrell-Criado V, Rodríguez-Muñiz GM, Yamaji M, Lhiaubet-Vallet V, Cuquerella MC, Miranda MA. Two-Photon Chemistry from Upper Triplet States of Thymine. J Am Chem Soc 2013; 135:16714-9. [DOI: 10.1021/ja408997j] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Victoria Vendrell-Criado
- Instituto
de Tecnología Química UPV-CSIC, Universitat Politècnica de València, Av. Los Naranjos s/n, 46022 Valencia, Spain
| | - Gemma M. Rodríguez-Muñiz
- Instituto
de Tecnología Química UPV-CSIC, Universitat Politècnica de València, Av. Los Naranjos s/n, 46022 Valencia, Spain
| | - Minoru Yamaji
- Division
of Molecular Science, Faculty of Science and Technology, Gunma University, Kiryu Gunma 376-8515, Japan
| | - Virginie Lhiaubet-Vallet
- Instituto
de Tecnología Química UPV-CSIC, Universitat Politècnica de València, Av. Los Naranjos s/n, 46022 Valencia, Spain
| | - M. Consuelo Cuquerella
- Instituto
de Tecnología Química UPV-CSIC, Universitat Politècnica de València, Av. Los Naranjos s/n, 46022 Valencia, Spain
| | - Miguel A. Miranda
- Instituto
de Tecnología Química UPV-CSIC, Universitat Politècnica de València, Av. Los Naranjos s/n, 46022 Valencia, Spain
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8
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Vogt RA, Reichardt C, Crespo-Hernández CE. Excited-State Dynamics in Nitro-Naphthalene Derivatives: Intersystem Crossing to the Triplet Manifold in Hundreds of Femtoseconds. J Phys Chem A 2013; 117:6580-8. [DOI: 10.1021/jp405656n] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- R. Aaron Vogt
- Department of Chemistry, Center
for Chemical Dynamics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Christian Reichardt
- Department of Chemistry, Center
for Chemical Dynamics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Carlos E. Crespo-Hernández
- Department of Chemistry, Center
for Chemical Dynamics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
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9
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Vogt RA, Gray TG, Crespo-Hernández CE. Subpicosecond Intersystem Crossing in Mono- and Di(organophosphine)gold(I) Naphthalene Derivatives in Solution. J Am Chem Soc 2012; 134:14808-17. [DOI: 10.1021/ja303592q] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- R. Aaron Vogt
- Department
of Chemistry and Center for Chemical Dynamics, Case Western Reserve University, Cleveland, Ohio 44106,
United States
| | - Thomas G. Gray
- Department
of Chemistry and Center for Chemical Dynamics, Case Western Reserve University, Cleveland, Ohio 44106,
United States
| | - Carlos E. Crespo-Hernández
- Department
of Chemistry and Center for Chemical Dynamics, Case Western Reserve University, Cleveland, Ohio 44106,
United States
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10
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Marazzi M, López-Delgado A, Fernández-González MA, Castaño O, Frutos LM, Temprado M. Modulating Nitric Oxide Release by S-Nitrosothiol Photocleavage: Mechanism and Substituent Effects. J Phys Chem A 2012; 116:7039-49. [DOI: 10.1021/jp304707n] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Marco Marazzi
- Departamento de Química Física, Universidad de Alcalá, E-28871 Alcalá
de Henares, Madrid, Spain
| | - Alberto López-Delgado
- Departamento de Química Física, Universidad de Alcalá, E-28871 Alcalá
de Henares, Madrid, Spain
| | | | - Obis Castaño
- Departamento de Química Física, Universidad de Alcalá, E-28871 Alcalá
de Henares, Madrid, Spain
| | - Luis Manuel Frutos
- Departamento de Química Física, Universidad de Alcalá, E-28871 Alcalá
de Henares, Madrid, Spain
| | - Manuel Temprado
- Departamento de Química Física, Universidad de Alcalá, E-28871 Alcalá
de Henares, Madrid, Spain
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11
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Sakamoto M, Majima T. Photochemistry for the Synthesis of Noble Metal Nanoparticles. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2010. [DOI: 10.1246/bcsj.20100097] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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12
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Reichardt C, Vogt RA, Crespo-Hernández CE. On the origin of ultrafast nonradiative transitions in nitro-polycyclic aromatic hydrocarbons: Excited-state dynamics in 1-nitronaphthalene. J Chem Phys 2009; 131:224518. [DOI: 10.1063/1.3272536] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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13
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Horvat M, Görner H, Warzecha KD, Neudörfl J, Griesbeck AG, Mlinarić-Majerski K, Basarić N. Photoinitiated domino reactions: N-(adamantyl)phthalimides and N-(adamantylalkyl)phthalimides. J Org Chem 2009; 74:8219-31. [PMID: 19874065 DOI: 10.1021/jo901753z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Phthalimides 1-6 undergo photochemical reactions upon direct irradiation as well as triplet sensitization and give rise to new products. Besides formation of the primary photoproducts, the first photochemical step initiates a subsequent thermal domino reaction or a domino sequence of a thermal and a photochemical reaction. The latter, involving two photochemical intramolecular gamma-H abstractions, was observed with phthalimides 1, 3, and 6 and delivered stereospecifically the hexacyclic benzazepine products 12, 19, and 27, respectively. The lowest triplet states of 1-6 were characterized in several solvents upon direct and acetone-sensitized excitation. The intermolecular electron transfer from triethylamine and DABCO was studied, and the radical anions were observed. Electrochemical measurements showed that intramolecular electron transfer from the adamantyl group of 1-6 to the lowest triplet state of the phthalimides is not feasible. The formation of products can be explained by intramolecular H-abstraction from the (alkyl)adamantane to the excited phthalimide, either from the excited singlet state or a hidden upper excited triplet state.
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Affiliation(s)
- Margareta Horvat
- Department of Organic Chemistry and Biochemistry, Ruder Bosković Institute, Bijenicka cesta 54, 10 000 Zagreb, Croatia
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14
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Zhang Y, Wang L, Moss RA, Platz MS. Ultrafast Spectroscopy of Arylchlorodiazirines: Hammett Correlations of Excited State Lifetimes. J Am Chem Soc 2009; 131:16652-3. [DOI: 10.1021/ja907915z] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Yunlong Zhang
- Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, and Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903
| | - Lei Wang
- Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, and Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903
| | - Robert A. Moss
- Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, and Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903
| | - Matthew S. Platz
- Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, and Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903
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15
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Collado-Fregoso E, Zugazagoitia JS, Plaza-Medina EF, Peon J. Excited-State Dynamics of Nitrated Push−Pull Molecules: The Importance of the Relative Energy of the Singlet and Triplet Manifolds. J Phys Chem A 2009; 113:13498-508. [PMID: 19839627 DOI: 10.1021/jp905379y] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Elisa Collado-Fregoso
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, México, 04510, D.F., Mexico
| | - Jimena S. Zugazagoitia
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, México, 04510, D.F., Mexico
| | - Eddy F. Plaza-Medina
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, México, 04510, D.F., Mexico
| | - Jorge Peon
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, México, 04510, D.F., Mexico
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16
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Zugazagoitia JS, Collado-Fregoso E, Plaza-Medina EF, Peon J. Relaxation in the Triplet Manifold of 1-Nitronaphthalene Observed by Transient Absorption Spectroscopy. J Phys Chem A 2009; 113:805-10. [DOI: 10.1021/jp8087397] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Jimena S. Zugazagoitia
- Universidad Nacional Autónoma de México, Instituto de Química, Ciudad Universitaria, 04510, México, D.F., México
| | - Elisa Collado-Fregoso
- Universidad Nacional Autónoma de México, Instituto de Química, Ciudad Universitaria, 04510, México, D.F., México
| | - Eddy F. Plaza-Medina
- Universidad Nacional Autónoma de México, Instituto de Química, Ciudad Universitaria, 04510, México, D.F., México
| | - Jorge Peon
- Universidad Nacional Autónoma de México, Instituto de Química, Ciudad Universitaria, 04510, México, D.F., México
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17
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Cai X, Yamaji M, Sakamoto M, Fujitsuka M, Majima T. The C–O bond dissociation of naphthoxymethyl compounds in the higher triplet excited state using two-color two-laser flash photolysis. Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2007.06.062] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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18
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Cai X, Sakamoto M, Yamaji M, Fujitsuka M, Majima T. CO-Bond Cleavage of Esters with a Naphthyl Group in the Higher Triplet Excited State during Two-Color Two-Laser Flash Photolysis. Chemistry 2007; 13:3143-9. [PMID: 17212365 DOI: 10.1002/chem.200600822] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A C-O-bond cleavage of esters having a naphthyl group, NpCO-OR and RCO-ONp (Np=alpha- and beta-naphthyl ((alpha)Np and (beta)Np, respectively), R=Ph and Me), was found during the two-color two-laser flash photolysis in acetonitrile. The C-O-bond cleavage occurred when NpCO-OR and RCO-ONp were excited to the singlet excited states (S1). On the other hand, no reaction occurred from the lowest triplet excited states (T1). When NpCO-OR(T1) and RCO-ONp(T1) were excited to the higher triplet excited states (Tn) using the second laser during the two-color two-laser flash photolysis, the C-O-bond cleavage occurred. The C-O-bond cleavage quantum yield (Phi) was estimated from the plots of the T1-state esters disappeared within a laser flash versus the second laser intensities. The C-O-bond cleavage in (beta)NpCO-OPh(Tn) occurred more efficiently than in (alpha)NpCO-OPh(Tn) and that in PhCO-O(beta)Np(Tn) occurred more efficiently than in PhCO-O(alpha)Np(Tn). The Phi value for ester with Ph and beta-Np groups was larger than that for ester with Ph and alpha-Np groups. The Phi value for MeCO-O(alpha)Np(Tn) was similar to those for PhCO-ONp(Tn), while that for MeCO-O(beta)Np(Tn) was much smaller than those for PhCO-ONp(Tn) and MeCO-O(alpha)Np(Tn). On the other hand, no C-O-bond cleavage was observed in NpCO-OMe(Tn). The Phi value depended on the characters of the groups (Np, Ph, and Me) on the ester. Whether R is Ph or Me with or without pi electron, respectively, is important for the C-O-bond cleavage. In other words, electronic delocalization of the T(n) state including Np and ester groups is necessary for the occurrence of the C-O-bond cleavage in NpCO-OR(Tn) and RCO-ONp(Tn).
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Affiliation(s)
- Xichen Cai
- The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan
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19
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Yamaji M, Kojima A, Tobita S. Stepwise Laser Photolysis Studies of β-Bond Cleavage in Highly Excited Triplet States of Biphenyl Derivatives Having C−O Bonds. J Phys Chem A 2007; 111:770-6. [PMID: 17266216 DOI: 10.1021/jp065782i] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Photochemical profiles of beta-bond dissociation in highly excited triplet states (Tn) of biphenyl derivatives having C-O bonds were investigated in solution, using stepwise laser photolysis techniques. The lowest triplet states (T1) were produced by triplet sensitization of acetone (Ac) upon 308-nm laser photolysis. The molar absorption coefficients of the T1 states were determined using triplet sensitization techniques. Any photochemical reactions were absent in the T1 states. Upon 355-nm laser flash photolysis of the T1 states, they underwent fragmentation, because of homolysis of the C-O bond in the Tn states from the observations of the transient absorption of the corresponding radicals. The quantum yields (Phidec) for the decomposition of the T1 states upon the second 355-nm laser excitation were determined. Based on the Phidec values and the bond dissociation energies (BDEs) for the C-O bond fission, the state energies (ERT) of the reactive highly excited triplet states (TR) were determined. It was revealed that (i) the Phidec was related to the energy difference (DeltaE) between the BDE and the ERT, and (ii) the rate (kdis) of beta-cleavage in the TR state was formulated as being simply proportional to DeltaE. The reaction mechanism for beta-bond cleavage in the TR states was discussed.
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Affiliation(s)
- Minoru Yamaji
- Department of Chemistry, Gunma University, Kiryu 376-8515, Japan.
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Direct fluorescence lifetime measurement of excited radical cation of 1,3,5-trimethoxybenzene by ns–ps two-color two-laser flash photolysis. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.10.102] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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