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Rieger P, Pueschmann S, Haas M, Schmallegger M, Guedes de la Cruz G, Griesser T. Exploring Aromatic S-Thioformates as Photoinitiators. Polymers (Basel) 2023; 15:polym15071647. [PMID: 37050262 PMCID: PMC10097006 DOI: 10.3390/polym15071647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 02/14/2023] [Accepted: 02/16/2023] [Indexed: 03/29/2023] Open
Abstract
Thiyl radicals were generated from aromatic S-thioformates by photolysis. The corresponding photo-initiated decarbonylation allows initiating polymerization reactions in both acrylate- and thiol-acrylate-based resin systems. Compared to aromatic thiols, the introduction of the photolabile formyl group prevents undesired reactions with acrylate monomers allowing photoinitiators (PIs) with constant reactivity over storage. To demonstrate the potential of S-thioformates as PIs, the bifunctional molecule S,S′-(thiobis(4,1-phenylene))dimethanethioate (2b) was synthesized, providing reactivity under visible light excitation. Consequently, acrylate-based formulations could successfully be processed by digital light processing (DLP)-based stereolithography at 405 nm in high resolution.
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Huang X, Orimoto Y, Aoki Y. Theoretical Analysis of Properties of Ground and Excited States for Photodissociation of the C-O Bond in Polycarbonates. J Phys Chem A 2021; 125:6662-6673. [PMID: 34319114 DOI: 10.1021/acs.jpca.1c03074] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Quantum chemical calculations were carried out to investigate the properties of the ground state (GS) and the excited state (ES) of bisphenol-A polycarbonate (PC) with bisphenol-A hydrogen carbonate (BPAHC) as a model compound. Time-dependent density functional theory (TDDFT) was used to obtain the absorption spectrum and the corresponding transition natures of BPAHC. Furthermore, the ESs related to the transitions of the carbonate group and neighboring phenyl ring were optimized employing the TDDFT method for photodegradation. Our results showed that the carbonate group is broken at an ES with relatively high energy, which has a significant C-O bond cleavage within the carbonate group compared to that of GS geometry. The carbonate group C-O bond cleavage is caused by two reasons. One is the transition from the O lone pair to the carbonate π anti-bonding which is commonly known, and the other one is the transition from the O lone pair to the phenyl group (adjacent to the carbonate group) π anti-bonding that is newly proposed.
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Affiliation(s)
- Xiao Huang
- Department of Material Sciences, Faculty of Engineering Sciences, Kyushu University, 6-1 Kasuga-Park, Fukuoka 816-8580, Japan
| | - Yuuichi Orimoto
- Department of Material Sciences, Faculty of Engineering Sciences, Kyushu University, 6-1 Kasuga-Park, Fukuoka 816-8580, Japan
| | - Yuriko Aoki
- Department of Material Sciences, Faculty of Engineering Sciences, Kyushu University, 6-1 Kasuga-Park, Fukuoka 816-8580, Japan.,Japan Science and Technology Agency, CREST, 4-1-8 Hon-chou, Kawaguchi, Saitama 332-0012, Japan
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Quindt MI, Gola GF, Ramirez JA, Bonesi SM. Photo-Fries Rearrangement of Some 3-Acylestrones in Homogeneous Media: Preparative and Mechanistic Studies. J Org Chem 2019; 84:7051-7065. [DOI: 10.1021/acs.joc.9b00786] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Matías I. Quindt
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Orgánica, Buenos Aires, C1428EGA, Argentina
- CONICET−Universidad de Buenos Aires, Centro de Investigaciones en Hidratos de Carbono (CIHIDECAR), Buenos Aires, C1428EGA, Argentina
| | - Gabriel F. Gola
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Orgánica, Buenos Aires, C1428EGA, Argentina
- CONICET−Universidad de Buenos Aires, Unidad de Microanálisis y Métodos Físicos Aplicados a Química Orgánica (UMYMFOR), Buenos Aires, C1428EHA, Argentina
| | - Javier A. Ramirez
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Orgánica, Buenos Aires, C1428EGA, Argentina
- CONICET−Universidad de Buenos Aires, Unidad de Microanálisis y Métodos Físicos Aplicados a Química Orgánica (UMYMFOR), Buenos Aires, C1428EHA, Argentina
| | - Sergio M. Bonesi
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Orgánica, Buenos Aires, C1428EGA, Argentina
- CONICET−Universidad de Buenos Aires, Centro de Investigaciones en Hidratos de Carbono (CIHIDECAR), Buenos Aires, C1428EGA, Argentina
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Siano G, Crespi S, Mella M, Bonesi SM. Selectivity in the Photo-Fries Rearrangement of Some Aryl Benzoates in Green and Sustainable Media. Preparative and Mechanistic Studies. J Org Chem 2019; 84:4338-4352. [DOI: 10.1021/acs.joc.9b00334] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Gastón Siano
- Departamento de Química Orgánica, CIHIDECAR − CONICET, Facultad de Ciencias Exactas y Naturales, University of Buenos Aires, 3er Piso, Pabellón 2, Ciudad Universitaria, Buenos Aires 1428, Argentina
| | - Stefano Crespi
- Dipartimento di Chimica, University of Pavia, Sezione Chimica Organica, v.le Taramelli 12, 27100 Pavia, Italy
| | - Mariella Mella
- Dipartimento di Chimica, University of Pavia, Sezione Chimica Organica, v.le Taramelli 12, 27100 Pavia, Italy
| | - Sergio M. Bonesi
- Departamento de Química Orgánica, CIHIDECAR − CONICET, Facultad de Ciencias Exactas y Naturales, University of Buenos Aires, 3er Piso, Pabellón 2, Ciudad Universitaria, Buenos Aires 1428, Argentina
- Dipartimento di Chimica, University of Pavia, Sezione Chimica Organica, v.le Taramelli 12, 27100 Pavia, Italy
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Toldo JM, Barbatti M, Gonçalves PFB. A three-state model for the photo-Fries rearrangement. Phys Chem Chem Phys 2017; 19:19103-19108. [DOI: 10.1039/c7cp03777e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photo-Fries rearrangement plays a central role in synthesis, but it is still unclear how it works. A three-state model can explain it.
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Affiliation(s)
- Josene M. Toldo
- Department of Physical Chemistry
- Federal University of Rio Grande do Sul
- Porto Alegre-RS
- Brazil
- Aix Marseille Univ
| | | | - Paulo F. B. Gonçalves
- Department of Physical Chemistry
- Federal University of Rio Grande do Sul
- Porto Alegre-RS
- Brazil
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7
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“Mono” and “bifunctional” aromatic esterificated benzophenone photoinitiators for free radical polymerization. Polym Bull (Berl) 2014. [DOI: 10.1007/s00289-014-1274-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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8
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Murdock D, Harris SJ, Luke J, Grubb MP, Orr-Ewing AJ, Ashfold MNR. Transient UV pump-IR probe investigation of heterocyclic ring-opening dynamics in the solution phase: the role played by nσ* states in the photoinduced reactions of thiophenone and furanone. Phys Chem Chem Phys 2014; 16:21271-9. [PMID: 25175813 DOI: 10.1039/c4cp03653k] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The heterocyclic ring-opening dynamics of thiophenone and furanone dissolved in CH3CN have been probed by ultrafast transient infrared spectroscopy. Following irradiation at 267 nm (thiophenone) or 225 nm (furanone), prompt (τ < 1 ps) ring-opening is confirmed by the appearance of a characteristic antisymmetric ketene stretching feature around 2150 cm(-1). The ring-opened product molecules are formed highly vibrationally excited, and cool subsequently on a ∼6.7 ps timescale. By monitoring the recovery of the parent (S0) bleach, it is found that ∼60% of the initially photoexcited thiophenone molecules reform the parent molecule, in stark contrast with the case in furanone where there is less than 10% parent bleach recovery. Complementary ab initio calculations of potential energy cuts along the S-C([double bond, length as m-dash]O) and O-C([double bond, length as m-dash]O) ring-opening coordinate reveals insights into the reaction mechanism, and the important role played by dissociative (n/π)σ* states in the UV-induced photochemistry of such heterocyclic systems.
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Affiliation(s)
- Daniel Murdock
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, UKBS8 1TS.
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9
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Pozdnyakov IP, Zhang X, Maksimova TA, Yanshole VV, Wu F, Grivin VP, Plyusnin VF. Wavelength-dependent photochemistry of acetaminophen in aqueous solutions. J Photochem Photobiol A Chem 2014. [DOI: 10.1016/j.jphotochem.2013.10.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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10
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Harris SJ, Murdock D, Grubb MP, Greetham GM, Clark IP, Towrie M, Ashfold MNR. Transient electronic and vibrational absorption studies of the photo-Claisen and photo-Fries rearrangements. Chem Sci 2014. [DOI: 10.1039/c3sc52893f] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Lu P, Lam JWY, Liu J, Jim CKW, Yuan W, Chan CYK, Xie N, Hu Q, Cheuk KKL, Tang BZ. Regioselective Alkyne Polyhydrosilylation: Synthesis and Photonic Properties of Poly(silylenevinylene)s. Macromolecules 2011. [DOI: 10.1021/ma201203w] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Ping Lu
- Fok Ying Tung Research Institute, The Hong Kong University of Science & Technology, Nansha, Guangzhou, China
- Department of Chemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun 130012, China
| | - Jacky W. Y. Lam
- Fok Ying Tung Research Institute, The Hong Kong University of Science & Technology, Nansha, Guangzhou, China
- Department of Chemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Jianzhao Liu
- Fok Ying Tung Research Institute, The Hong Kong University of Science & Technology, Nansha, Guangzhou, China
- Department of Chemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Cathy K. W. Jim
- Fok Ying Tung Research Institute, The Hong Kong University of Science & Technology, Nansha, Guangzhou, China
- Department of Chemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Wangzhang Yuan
- Fok Ying Tung Research Institute, The Hong Kong University of Science & Technology, Nansha, Guangzhou, China
- Department of Chemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Carrie Y. K. Chan
- Fok Ying Tung Research Institute, The Hong Kong University of Science & Technology, Nansha, Guangzhou, China
- Department of Chemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Ni Xie
- Fok Ying Tung Research Institute, The Hong Kong University of Science & Technology, Nansha, Guangzhou, China
- Department of Chemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Qin Hu
- Fok Ying Tung Research Institute, The Hong Kong University of Science & Technology, Nansha, Guangzhou, China
- Department of Chemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Kevin K. L. Cheuk
- The Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong, China
| | - Ben Zhong Tang
- Fok Ying Tung Research Institute, The Hong Kong University of Science & Technology, Nansha, Guangzhou, China
- Department of Chemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
- Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, China
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Bach T, Hehn JP. Photochemical reactions as key steps in natural product synthesis. Angew Chem Int Ed Engl 2011; 50:1000-45. [PMID: 21246702 DOI: 10.1002/anie.201002845] [Citation(s) in RCA: 581] [Impact Index Per Article: 44.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Indexed: 12/15/2022]
Abstract
Photochemical reactions contribute in a significant way to the existing repertoire of carbon-carbon bond-forming reactions by allowing access to exceptional molecular structures that cannot be obtained by conventional means. In this Review, the most important photochemical transformations that have been employed in natural product synthesis are presented. Selected total syntheses are discussed as examples, with particular attention given to the photochemical key step and its stereoselectivity. The structural relationship between the photochemically generated molecule and the natural product is shown, and, where necessary, the consecutive reactions in the synthesis are illustrated and classified.
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Affiliation(s)
- Thorsten Bach
- Lehrstuhl für Organische Chemie I, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
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13
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Bach T, Hehn JP. Photochemische Reaktionen als Schlüsselschritte in der Naturstoffsynthese. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201002845] [Citation(s) in RCA: 177] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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14
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Gohdo M, Takamasu T, Wakasa M. Photochemical primary process of photo-Fries rearrangement reaction of 1-naphthyl acetate as studied by MFEprobe. Phys Chem Chem Phys 2011; 13:755-61. [DOI: 10.1039/c0cp00077a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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15
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Gohdo M, Wakasa M. Reexamination of the Photochemical Primary Process of Photo-Fries Rearrangement Reaction as Studied by MFE Probe. CHEM LETT 2010. [DOI: 10.1246/cl.2010.106] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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16
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Jim CKW, Qin A, Lam JWY, Häussler M, Liu J, Yuen MMF, Kim JK, Ng KM, Tang BZ. Facile Polycyclotrimerization of “Simple” Arylene Bipropiolates: A Metal-Free, Regioselective Route to Functional Hyperbranched Polymers with High Optical Transparency, Tunable Refractive Index, Low Chromatic Aberration, and Photoresponsive Patternability. Macromolecules 2009. [DOI: 10.1021/ma900076z] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
| | - Anjun Qin
- Department of Polymer Science and Engineering, Key Laboratory of Macromolecular Synthesis and Functionalization of the Ministry of Education of China, Zhejiang University, Hangzhou 310027, China
| | | | | | | | | | | | | | - Ben Zhong Tang
- Department of Polymer Science and Engineering, Key Laboratory of Macromolecular Synthesis and Functionalization of the Ministry of Education of China, Zhejiang University, Hangzhou 310027, China
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Griesser T, Höfler T, Jakopic G, Belzik M, Kern W, Trimmel G. Refractive index modulation in polymers bearing photoreactive phenyl and naphthyl ester units using different UV wavelengths. ACTA ACUST UNITED AC 2009. [DOI: 10.1039/b903410b] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Griesser T, Adams J, Wappel J, Kern W, Leggett GJ, Trimmel G. Micrometer and nanometer scale patterning using the photo-fries rearrangement: toward selective execution of molecular transformations with nanoscale spatial resolution. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:12420-12425. [PMID: 18837527 DOI: 10.1021/la802382p] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The photolithographic modification of monolayers provides a versatile and powerful means of fabricating functionalized nanostructured surfaces. In this contribution, we present photosensitive thiol-bearing aryl ester groups which are capable of undergoing the so-called photo-Fries rearrangement to yield hydroxyketones. Phenyl 16-mercaptohexadecanoate was prepared by a three-step synthesis. This molecule undergoes a photoisomerization reaction upon illumination with UV light at ca. 250 nm. Subsequently this molecule was applied as a self-assembled monolayer on gold. Following photochemical modification, the adsorbates were selectively derivatized to yield amino-functionalized surfaces using a simple two-step reaction. This reaction was monitored by X-ray photoelectron spectroscopy and contact angle measurements and friction force microscopy. Micrometer-scale patterned surfaces were produced using a contact mask in conjunction with a frequency-doubled argon ion laser (lambda=244 nm). Near-field optical exposure was carried out by coupling the laser to a scanning near-field optical microscope and yielded nanometer-scale resolution. Following derivatization, the resulting structures were analyzed by friction force microscopy. Clear contrast was observed in the friction signal following surface modification.
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Affiliation(s)
- Thomas Griesser
- Institute for Chemistry and Technology of Materials (ICTM), Graz University of Technology, Stremayrgasse 16, 8010 Graz, Austria
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Höfler T, Grießer T, Gruber M, Jakopic G, Trimmel G, Kern W. Photo-Fries Rearrangement in Polymeric Media: An Investigation on Fully Aromatic Esters Containing the Naphthyl Chromophore. MACROMOL CHEM PHYS 2008. [DOI: 10.1002/macp.200700456] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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20
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Daschiel U, Höfler T, Jakopic G, Schmidt V, Kern W. Selected Polymers that Contain Aromatic Ester Units: Synthesis, Photoreactions, and Refractive Index Modulation. MACROMOL CHEM PHYS 2007. [DOI: 10.1002/macp.200700035] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Schalk O, Unterreiner AN. Ultrafast Relaxation Dynamics of Perchlorinated Cycloheptatriene in Solution. J Phys Chem A 2007; 111:3231-40. [PMID: 17428037 DOI: 10.1021/jp066193f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The photochemistry of perchlorinated cycloheptatriene (CHTCl(8)) has been studied by means of ultrafast pump-probe, transient anisotropy and continuous UV-irradiation experiments in various solvents as well as by DFT calculations. After UV-excitation to the 1A' '-state, two competing reactions occur--a [1,7]-sigmatropic chlorine migration via two ultrafast internal conversions and a [4,5]-electrocyclization forming octachlorobicylo[3.2.0]hepta-[2,6]-diene. The first reaction has been studied by excitation with a 263 nm femtosecond-laser pulse. Pump-probe experiments reveal a first, solvent-independent time constant, tau1(CHTCl(8)) = 140 fs, that can be associated with the electronic relaxation of the 2A'-1A' ' transition, while a second one, tau2(CHTCl(8)), ranges from 0.9 to 1.8 ps depending on the polarity of the solvent. This finding is consistent with a [1,7]-chlorine migration during the 1A'-2A' transition where the migrating chlorine atom is partly negatively charged. The charge separation has also been confirmed by DFT calculations. Transient anisotropy measurements result in a time zero value of r(0) = 0.35 after deconvolution and a decay constant of tau1(a) = 120 fs, which can be explained by vibrational motions of CHTCl(8) in the electronically excited states, 1A' ' and 2A'. After continuous UV-irradiation of CHTCl(8), octachlorobicylo[3.2.0]hepta-[2,6]-diene is primarily formed with a solvent-dependent yield. From these investigations, we suggest a relaxation mechanism for CHTCl(8) after photoexcitation that is comparable to cycloheptatriene.
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Affiliation(s)
- O Schalk
- Institut für Physikalische Chemie, Kaiserstr. 12, 76128 Karlsruhe Universität Karlsruhe (TH), Germany
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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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Höfler T, Grießer T, Gstrein X, Trimmel G, Jakopic G, Kern W. UV reactive polymers for refractive index modulation based on the photo-Fries rearrangement. POLYMER 2007. [DOI: 10.1016/j.polymer.2007.01.041] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Zarkadis AK, Georgakilas V, Perdikomatis GP, Trifonov A, Gurzadyan GG, Skoulika S, Siskos MG. Triplet- vs. singlet-state imposed photochemistry. The role of substituent effects on the photo-Fries and photodissociation reaction of triphenylmethyl silanes. Photochem Photobiol Sci 2005; 4:469-80. [PMID: 15920631 DOI: 10.1039/b502089a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The photochemistry of three structurally very similar triphenylmethylsilanes 1, 2, 3 [p-X-C(6)H(4)-CPh(2)-SiMe(3): X = PhCO, 1; H, ; Ph(OCH(2)CH(2)O)C, 3] is described by means of 248 and 308 nm nanosecond laser flash photolysis (ns-LFP), femtosecond LFP, EPR spectroscopy, emission spectroscopy (fluorescence, phosphorescence), ns-pulse radiolysis (ns-PR), photoproduct analysis studies in MeCN, and X-ray crystallographic analysis of the two key-compounds 1 and 2. The photochemical behavior of 1, 2 and 3 is discussed and compared with that of a fourth one, 4, bearing on the p-position an amino group (X = Me(2)N) and whose detailed photochemistry we reported earlier (J. Org. Chem., 2000, 65, 4274-4280). Silane 1 undergoes on irradiation with 248 and 308 nm laser light a fast photodissociation of the C-Si bond giving the p-(benzoyl)triphenylmethyl radical (1*) with a rate constant of k(diss)= 3 x 10(7) s(-1). The formation of 1* is a one-quantum process and takes place via the carbonyl triplet excited state with high quantum yield (Phi(rad)= 0.9); the intervention of the triplet state is clearly demonstrated through the phosphorescence spectrum and quenching experiments with ferrocene (k(q)= 9.3 x 10(9) M(-1) s(-1)), Et(3)N (1.1 x 10(9) M(-1) s(-1)), and styrene (3.1 x 10(9) M(-1) s(-1)) giving quenching rate constants very similar to those of benzophenone. For comparative reasons radical 1* was generated independently from p-(benzoyl)triphenylmethyl bromide via pulse radiolysis in THF and its absorption coefficient at lambda(max)= 340 nm was determined ([epsilon]= 27770 M(-1) cm(-1)). We found thus that the p-PhCO-derivative 1 behaves similar to the p-Me(2)N one (the latter giving the p-(dimethylamino)triphenylmethyl radical with Phi(rad)= 0.9), irrespective of their completely different ground state electronic properties. In contrast, compounds 2, 3 that bear only the aromatic chromophore give by laser or lamp irradiation both, (i) radical products [Ph(3)C* and p-Ph(OCH(2)CH(2)O)C-C(6)H(4)-C(*)Ph(2), respectively] after dissociation of the central C-Si bond (Phi(rad)= 0.16), and (ii) persistent photo-Fries rearrangement products (of the type of 5-methylidene-6-trimethylsilyl-1,3-cyclohexadiene) absorbing at 300-450 nm and arising from a 1,3-shift of the SiMe(3) group from the benzylic to the ortho-position of the aromatic ring (Phi approximately 0.85 for 2). Using fs-LFP on 2 we showed that the S(1) state recorded at 100 fs after the pulse decays on a time scale of 500 fs giving Ph(3)C* through C-Si bond dissociation. In a second step and within the next 10 ps trityl radicals either escape from the solvent cage (the quantum yield of Ph(3)C* formation Phi(rad)= 0.16 was measured with ns-LFP), or undergo in-cage recombination to photo-Fries products. Thus, singlet excited states (S(1)) of the aromatic organosilanes (2, 3) prefer photo-Fries rearrangement products, while triplet excited states (1, 4) favor free radicals. Both reactions proceed via a common primary photodissociation step (C-Si bond homolysis) and differentiate obviously in the multiplicity of the resulting geminate radical pairs; singlet radical pairs give preferably photo-Fries products following an in-cage recombination, while triplet radical pairs escape the solvent cage (MeCN). The results demonstrate the crucial role which is played by the chromophore which prescribes in a sense, (i) the multiplicity of the intervening excited state and consequently that of the resulting geminate radical pair, and (ii) the dominant reaction path to be followed: the benzophenone- and anilino-chromophore present in silanes 1 and 4, respectively, impose effective intersystem crossing transitions (k(isc)= 10(11) s(-1) and 6 x 10(8) s(-1), respectively) leading to triplet states and finally to free radical products, while the phenyl chromophore in 2 and 3, possessing ineffective isc (k(isc)= 6 x 10(6) s(-1)) leads to photo-Fries product formation via the energetic high lying S(1) state [approximately 443 kJ mol(-1)(106 kcal mol(-1))].
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