1
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Li H, Gong X, Ni H, Lu P, Luo X, Wen J, Yang Y, Qian X, Sun Z, Wu J. Light-Induced Ultrafast Molecular Dynamics: From Photochemistry to Optochemistry. J Phys Chem Lett 2022; 13:5881-5893. [PMID: 35730581 PMCID: PMC9251772 DOI: 10.1021/acs.jpclett.2c01119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
By precisely controlling the waveform of ultrashort laser fields, electronic and nuclear motions in molecules can be steered on extremely short time scales, even in the attosecond regime. This new research field, termed "optochemistry", presents the light field in the time-frequency domain and opens new avenues for tailoring molecular reactions beyond photochemistry. This Perspective summarizes the ultrafast laser techniques employed in recent years for manipulating the molecular reactions based on waveform control of intense ultrashort laser pulses, where the chemical reactions can take place in isolated molecules, clusters, and various nanosystems. The underlying mechanisms for the coherent control of molecular dynamics are explicitly explored. Challenges and opportunities coexist in the field of optochemistry. Advanced technologies and theoretical modeling are still being pursued, with great prospects for controlling chemical reactions with unprecedented spatiotemporal precision.
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Affiliation(s)
- Hui Li
- State
Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Xiaochun Gong
- State
Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Hongcheng Ni
- State
Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Peifen Lu
- State
Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Xiao Luo
- School
of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
| | - Jin Wen
- State
Key Laboratory for Modification of Chemical Fibers and Polymer Materials,
College of Materials Science and Engineering, Donghua University, Shanghai 201620, China
| | - Youjun Yang
- State
Key Laboratory of Bioreactor Engineering, Shanghai Key Laboratory
of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Xuhong Qian
- State
Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
- School
of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
| | - Zhenrong Sun
- State
Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Jian Wu
- State
Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
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2
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Usui R, Yamamoto K, Okajima H, Mutoh K, Sakamoto A, Abe J, Kobayashi Y. Photochromic Radical Complexes That Show Heterolytic Bond Dissociation. J Am Chem Soc 2020; 142:10132-10142. [PMID: 32363867 DOI: 10.1021/jacs.0c02739] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photochromic materials have been widely used in various research fields because of their variety of photoswitching properties based on various molecular frameworks and bond breaking processes, such as homolysis and heterolysis. However, while a number of photochromic molecular frameworks have been reported so far, there are few reports on photochromic molecular frameworks that show both homolysis and heterolysis depending on the substituents with high durability. The biradicals and zwitterions generated by homolysis and heterolysis have different physical and chemical properties and different potential applications. Therefore, the rational photochromic molecular design to control the bond dissociation in the excited state on demand expands the versatility for photoswitch materials beyond the conventional photochromic molecular frameworks. In this study, we synthesized novel photochromic molecules based on the framework of a radical-dissociation-type photochromic molecule: phenoxyl-imidazolyl radical complex (PIC). While the conventional PIC shows the photoinduced homolysis, the substitution of a strong electron-donating moiety to the phenoxyl moiety enables the bond dissociation process to be switched from homolysis to heterolysis. This study gives a strategy for controlling the bond dissociation process of the excited state of photochromic systems, and the strategy enables us to develop further novel radical and zwitterionic photoswitches.
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Affiliation(s)
- Ryosuke Usui
- Department of Applied Chemistry, College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan
| | - Katsuya Yamamoto
- Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan
| | - Hajime Okajima
- Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan
| | - Katsuya Mutoh
- Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan
| | - Akira Sakamoto
- Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan
| | - Jiro Abe
- Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan
| | - Yoichi Kobayashi
- Department of Applied Chemistry, College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan
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3
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Breloy L, Negrell C, Mora AS, Li WSJ, Brezová V, Caillol S, Versace DL. Vanillin derivative as performing type I photoinitiator. Eur Polym J 2020. [DOI: 10.1016/j.eurpolymj.2020.109727] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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4
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Kim SH, Jang M, Moon DY, Park BS. Leaving group effect on photochemistry of ortho-alkylphenacyl carboxylate. Tetrahedron Lett 2018. [DOI: 10.1016/j.tetlet.2018.10.042] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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5
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Schüppel F, Roos MK, de Vivie-Riedle R. Ultrafast non-adiabatic dynamics of excited diphenylmethyl bromide elucidated by quantum dynamics and semi-classical on-the-fly dynamics. Phys Chem Chem Phys 2018; 20:22753-22761. [PMID: 30140797 DOI: 10.1039/c8cp03257b] [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
Carbocations and carboradicals are key intermediates in organic chemistry. Typically UV laser excitation is used to induce homolytical or heterolytical bond cleavage in suitable precursor molecules. Of special interest hereby are diphenylmethyl compounds (Ph2CH-X) with X = Cl, Br as a leaving group as they form diphenylmethyl radicals (Ph2CH˙) and cations (Ph2CH+) within a femtosecond time scale in polar solvents. In this work, we build on our methodology developed for the chlorine case and investigate the photodissociation reaction of Ph2CH-Br by state-of-the-art theoretical methods. On the one hand, we employ specially adapted reactive coordinates for a grid-based wave packet dynamics in reduced dimensionality using the Wilson G-matrix ansatz for the kinetic part of the Hamiltonian. On the other hand, we use full-dimensional semiclassical on-the-fly dynamics with Tully's fewest switches surface hopping routine for comparison. We apply both methods to explain remarkable differences in experimental transient absorption measurements for Cl or Br as the leaving group. The wave packet motion, visible only for the bromine leaving group, can be related to the crucial role of the central carbon atom, which undergoes rehybridization from sp3 to sp2 during the photoinduced bond cleavage. Comparable features are the two consecutive conical intersections near the Franck-Condon region controlling the product splitting to Ph2CH˙/Br˙ and Ph2CH+/Br- as well as the difference in delay time for the respective product formation.
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Affiliation(s)
- Franziska Schüppel
- Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany.
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6
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Kumara MN, Nakahara T, Kobayashi S, Fujio M, Mishima M. Nucleophilicities of Alcohols and Water in Acetonitrile Based on Reactivities of Benzhydrylium Ions. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2018. [DOI: 10.1246/bcsj.20170360] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Manikyanahally N. Kumara
- Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Tesshu Nakahara
- Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Shinjiro Kobayashi
- Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Mizue Fujio
- Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Masaaki Mishima
- Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
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7
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Park JH, Hughs M, Chung TS, Ayitou AJL, Breslin VM, Garcia-Garibay MA. Generation and Reactivity Studies of Diarylmethyl Radical Pairs in Crystalline Tetraarylacetones via Laser Flash Photolysis Using Nanocrystalline Suspensions. J Am Chem Soc 2017; 139:13312-13317. [PMID: 28844142 DOI: 10.1021/jacs.7b04449] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The nanosecond electronic spectra and kinetics of the radical pairs from various crystalline tetraarylacetones were obtained using transmission laser flash photolysis methods by taking advantage of aqueous nanocrystalline suspensions in the presence of submicellar CTAB, which acts as a surface passivator. After showing that all tetraarylacetones react efficiently by a photodecarbonylation reaction in the crystalline state, we were able to detect the intermediate radical pairs within the ca. 8 ns laser pulse of our laser setup. We showed that the solid-state spectra of the radical pairs are very similar to those detected in solution, with λmax in the 330-360 nm range. Kinetics in the solid state was observed to be biexponential and impervious to the presence of oxygen or variations in laser power. A relatively short-lived component (0.3-1.7 μs) accounts for only 3-8% of the total decay with a longer-lived component having a time constant in the range of 40-90 μs depending on the nature of the substituents.
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Affiliation(s)
- Jin H Park
- Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States
| | - Melissa Hughs
- Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States
| | - Tim S Chung
- Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States
| | - A Jean-Luc Ayitou
- Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States
| | - Vanessa M Breslin
- Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States
| | - Miguel A Garcia-Garibay
- Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States
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8
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Masui Y, Hattori T, Onaka M. Reversible Generation of Labile Secondary Carbocations from Alcohols in the Nanospace of H-Mordenite and Their Long-Lasting Preservation at Ambient Temperature. J Am Chem Soc 2017; 139:8612-8620. [PMID: 28565906 DOI: 10.1021/jacs.7b03336] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Secondary carbocations are rarely observed spectrometrically for prolonged durations at ambient temperatures because of their instability. In this study, when 4,4'-difluorobenzhydrol (1) was mixed with H-mordenite (H-Mor), the 4,4'-difluorodiphenylmethyl cation (2) was generated as the main product, identified by UV-vis and 13C-MAS NMR spectroscopies, and was preserved for over 1 week at ambient temperature. Surprisingly, the polymerization and disproportionation of 1 barely proceeded within the micropores of H-Mor. However, these side reactions prevailed in TfOH and formation of 2 was not observed. Preservation of other secondary carbocations from benzhydrol, 4,4'-dichlorobenzhydrol, and 9-fluorenol was also realized in H-Mor. It was confirmed that the generation of 2 from 1 was controlled by thermodynamic equilibrium rather than kinetic regulations. The equilibrium between 2 and 1 was accompanied by reversible chromism, which could be easily controlled by altering the moisture content in H-Mor. Moreover, novel insights into specific acid catalysis in zeolites densely populated with acid sites on the inner surface of micropores are described herein.
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Affiliation(s)
- Yoichi Masui
- Graduate School of Arts and Sciences, The University of Tokyo , 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Taiki Hattori
- Graduate School of Science, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Makoto Onaka
- Graduate School of Arts and Sciences, The University of Tokyo , 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
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9
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Thallmair S, Roos MK, de Vivie-Riedle R. Molecular features in complex environment: Cooperative team players during excited state bond cleavage. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2016; 3:043205. [PMID: 26958588 PMCID: PMC4752547 DOI: 10.1063/1.4941600] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 12/22/2015] [Indexed: 06/05/2023]
Abstract
Photoinduced bond cleavage is often employed for the generation of highly reactive carbocations in solution and to study their reactivity. Diphenylmethyl derivatives are prominent precursors in polar and moderately polar solvents like acetonitrile or dichloromethane. Depending on the leaving group, the photoinduced bond cleavage occurs on a femtosecond to picosecond time scale and typically leads to two distinguishable products, the desired diphenylmethyl cations (Ph2CH(+)) and as competing by-product the diphenylmethyl radicals ([Formula: see text]). Conical intersections are the chief suspects for such ultrafast branching processes. We show for two typical examples, the neutral diphenylmethylchloride (Ph2CH-Cl) and the charged diphenylmethyltriphenylphosphonium ions ([Formula: see text]) that the role of the conical intersections depends not only on the molecular features but also on the interplay with the environment. It turns out to differ significantly for both precursors. Our analysis is based on quantum chemical and quantum dynamical calculations. For comparison, we use ultrafast transient absorption measurements. In case of Ph2CH-Cl, we can directly connect the observed signals to two early three-state and two-state conical intersections, both close to the Franck-Condon region. In case of the [Formula: see text], dynamic solvent effects are needed to activate a two-state conical intersection at larger distances along the reaction coordinate.
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Affiliation(s)
| | - Matthias K Roos
- Department Chemie, Ludwig-Maximilians-Universität München , D-81377 München, Germany
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10
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Barbieri A, De Carlo Chimienti R, Del Giacco T, Di Stefano S, Lanzalunga O, Lapi A, Mazzonna M, Olivo G, Salamone M. Oxidation of Aryl Diphenylmethyl Sulfides Promoted by a Nonheme Iron(IV)-Oxo Complex: Evidence for an Electron Transfer-Oxygen Transfer Mechanism. J Org Chem 2016; 81:2513-20. [PMID: 26886491 DOI: 10.1021/acs.joc.6b00099] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The oxidation of a series of aryl diphenylmethyl sulfides (4-X-C6H4SCH(C6H5)2, where X = OCH3 (1), X = CH3 (2), X = H (3), and X = CF3 (4)) promoted by the nonheme iron(IV)-oxo complex [(N4Py)Fe(IV)═O](2+) occurs by an electron transfer-oxygen transfer (ET-OT) mechanism as supported by the observation of products (diphenylmethanol, benzophenone, and diaryl disulfides) deriving from α-C-S and α-C-H fragmentation of radical cations 1(+•)-4(+•), formed besides the S-oxidation products (aryl diphenylmethyl sulfoxides). The fragmentation/S-oxidation product ratios regularly increase through a decrease in the electron-donating power of the aryl substituents, that is, by increasing the fragmentation rate constants of the radical cations as indicated by a laser flash photolysis (LFP) study of the photochemical oxidation of 1-4 carried out in the presence of N-methoxyphenanthridinium hexafluorophosphate (MeOP(+)PF6(-)).
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Affiliation(s)
- Alessia Barbieri
- Dipartimento di Chimica and Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione c/o Dipartimento di Chimica, Università degli Studi di Roma "La Sapienza" , P. le A. Moro 5, 00185 Rome, Italy
| | - Rosemilia De Carlo Chimienti
- Dipartimento di Chimica and Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione c/o Dipartimento di Chimica, Università degli Studi di Roma "La Sapienza" , P. le A. Moro 5, 00185 Rome, Italy
| | - Tiziana Del Giacco
- Dipartimento di Chimica, Biologia e Biotecnologie and Centro di Eccellenza Materiali Innovativi Nanostrutturati, Università di Perugia , Via Elce di Sotto 8, 06123 Perugia, Italy
| | - Stefano Di Stefano
- Dipartimento di Chimica and Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione c/o Dipartimento di Chimica, Università degli Studi di Roma "La Sapienza" , P. le A. Moro 5, 00185 Rome, Italy
| | - Osvaldo Lanzalunga
- Dipartimento di Chimica and Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione c/o Dipartimento di Chimica, Università degli Studi di Roma "La Sapienza" , P. le A. Moro 5, 00185 Rome, Italy
| | - Andrea Lapi
- Dipartimento di Chimica and Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione c/o Dipartimento di Chimica, Università degli Studi di Roma "La Sapienza" , P. le A. Moro 5, 00185 Rome, Italy
| | - Marco Mazzonna
- Dipartimento di Chimica and Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione c/o Dipartimento di Chimica, Università degli Studi di Roma "La Sapienza" , P. le A. Moro 5, 00185 Rome, Italy
| | - Giorgio Olivo
- Dipartimento di Chimica and Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione c/o Dipartimento di Chimica, Università degli Studi di Roma "La Sapienza" , P. le A. Moro 5, 00185 Rome, Italy
| | - Michela Salamone
- Dipartimento di Scienze e Tecnologie Chimiche, Università "Tor Vergata" , Via della Ricerca Scientifica 1, I-00133 Rome, Italy
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11
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Bettoni M, Del Giacco T, Stradiotto M, Elisei F. Photoinduced One-Electron Oxidation of Benzyl Methyl Sulfides in Acetonitrile: Time-Resolved Spectroscopic Evidence for a Thionium Ion Intermediate. J Org Chem 2015; 80:8001-8. [DOI: 10.1021/acs.joc.5b01052] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Marta Bettoni
- Dipartimento
di Ingegneria Civile ed Ambientale, ‡Dipartimento di Chimica, Biologia
e Biotecnologie, and §Centro di Eccellenza Materiali Innovativi Nanostrutturati (CEMIN), Università di Perugia, 06123 Perugia, Italy
| | - Tiziana Del Giacco
- Dipartimento
di Ingegneria Civile ed Ambientale, ‡Dipartimento di Chimica, Biologia
e Biotecnologie, and §Centro di Eccellenza Materiali Innovativi Nanostrutturati (CEMIN), Università di Perugia, 06123 Perugia, Italy
| | - Marina Stradiotto
- Dipartimento
di Ingegneria Civile ed Ambientale, ‡Dipartimento di Chimica, Biologia
e Biotecnologie, and §Centro di Eccellenza Materiali Innovativi Nanostrutturati (CEMIN), Università di Perugia, 06123 Perugia, Italy
| | - Fausto Elisei
- Dipartimento
di Ingegneria Civile ed Ambientale, ‡Dipartimento di Chimica, Biologia
e Biotecnologie, and §Centro di Eccellenza Materiali Innovativi Nanostrutturati (CEMIN), Università di Perugia, 06123 Perugia, Italy
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12
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Cyr D, Das P. Quenching of diphenylmethyl radical fluorescence by cyanoaromatics and phenols. RESEARCH ON CHEMICAL INTERMEDIATES 2015. [DOI: 10.1007/s11164-014-1914-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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13
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Mayr H, Ammer J, Baidya M, Maji B, Nigst TA, Ofial AR, Singer T. Scales of Lewis basicities toward C-centered Lewis acids (carbocations). J Am Chem Soc 2015; 137:2580-99. [PMID: 25555037 DOI: 10.1021/ja511639b] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Equilibria for the reactions of benzhydryl cations (Ar2CH(+)) with phosphines, tert-amines, pyridines, and related Lewis bases were determined photometrically in CH2Cl2 and CH3CN solution at 20 °C. The measured equilibrium constants can be expressed by the sum of two parameters, defined as the Lewis Acidity (LA) of the benzhydrylium ions and the Lewis basicity (LB) of the phosphines, pyridines, etc. Least-squares minimization of log K = LA + LB with the definition LA = 0 for (4-MeOC6H4)2CH(+) gave a Lewis acidity scale for 18 benzhydrylium ions covering 18 orders of magnitude in CH2Cl2 as well as Lewis basicities (with respect to C-centered Lewis acids) for 56 bases. The Lewis acidities correlated linearly with the quantum chemically calculated (B3LYP/6-311++G(3df,2pd)//B3LYP/6-31G(d,p) level) methyl anion affinities of the corresponding benzhydrylium ions, which can be used as reference compounds for characterizing a wide variety of Lewis bases. The equilibrium measurements were complemented by isothermal titration calorimetry studies. Rates of SN1 solvolyses of benzhydryl chlorides, bromides, and tosylates derived from E(13-33)(+), i.e., from highly reactive carbocations, correlate excellently with the corresponding Lewis acidities and the quantum chemically calculated methyl anion affinities. This correlation does not hold for solvolyses of derivatives of the better stabilized amino-substituted benzhydrylium ions E(1-12)(+). In contrast, the correlation between electrophilic reactivities and Lewis acidities (or methyl anion affinities) is linear for all donor-substituted benzhydrylium ions E(1-21)(+), while the acceptor-substituted benzhydrylium ions E(26-33)(+) react more slowly than expected from their thermodynamic stabilities. The boundaries of linear rate-equilibrium relationships were thus defined.
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Affiliation(s)
- Herbert Mayr
- Department Chemie, Ludwig-Maximilians-Universität München , Butenandtstraße 5-13, Haus F, 81377 München, Germany
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14
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Cyr D, Das P. Kinetics of C–C and C–H Bond Cleavage in Phenyl Alkane Radical Cations Generated by Photoinduced Electron Transfer. J Phys Chem A 2014; 118:11155-67. [DOI: 10.1021/jp508556z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Douglas Cyr
- Physical
Sciences Department, Cameron University, Lawton, Oklahoma 73505, United States
| | - Paritosh Das
- Physical
Sciences Department, Cameron University, Lawton, Oklahoma 73505, United States
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15
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Kendale J, Valentín EM, Woerpel KA. Solvent effects in the nucleophilic substitutions of tetrahydropyran acetals promoted by trimethylsilyl trifluoromethanesulfonate: trichloroethylene as solvent for stereoselective C- and O-glycosylations. Org Lett 2014; 16:3684-7. [PMID: 24991982 PMCID: PMC4334250 DOI: 10.1021/ol501471c] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Indexed: 12/03/2022]
Abstract
The selectivities of nucleophilic substitution reactions of tetrahydropyran acetals promoted by trimethylsilyl trifluoromethanesulfonate depend upon the reaction solvent. Polar solvents favor the formation of S(N)1 products, while nonpolar solvents favor S(N)2 products. Trichloroethylene was identified as the solvent most likely to give S(N)2 products in both C- and O-glycosylation reactions.
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Affiliation(s)
- Joanna
C. Kendale
- Department
of Chemistry, New York University, New York, New York 10003, United States
| | - Elizabeth M. Valentín
- Department
of Chemistry, New York University, New York, New York 10003, United States
| | - K. A. Woerpel
- Department
of Chemistry, New York University, New York, New York 10003, United States
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16
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Thallmair S, Fingerhut BP, de Vivie-Riedle R. Ground and Excited State Surfaces for the Photochemical Bond Cleavage in Phenylmethylphenylphosphonium Ions. J Phys Chem A 2013; 117:10626-33. [DOI: 10.1021/jp403082r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sebastian Thallmair
- Department
Chemie, Ludwig-Maximilians-Universität München, D-81377 München, Germany
- Lehrstuhl
für BioMolekulare Optik, Ludwig-Maximilians-Universität München, D-80538 München, Germany
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17
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Dockheer SM, Gubler L, Koppenol WH. Reactions of the tetraoxidosulfate(˙-) and hydroxyl radicals with poly(sodium α-methylstyrene sulfonate). Phys Chem Chem Phys 2013; 15:4975-83. [PMID: 23443676 DOI: 10.1039/c3cp44341h] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Poly(α-methylstyrene sulfonic acid) (PAMS) represents a class of polymers that can form the protogenic constituent in electrolyte membranes for fuel cells. Oxidative stress is thought to play an important role in the degradation of the fuel cell membranes. Having previously established that damage may be mediated via abstraction of a benzylic hydrogen, we examined model compounds similar to those used before, but with a methyl group at the α-position. We studied the reaction of HO˙ and SO4(˙-), generated by pulse radiolysis, with model compounds in aqueous solution, and measured k = (2 ± 0.5) × 10(10) M(-1) s(-1) and (2 - 3) × 10(10) M(-1) s(-1) for the reaction of HO˙ with PAMS with average molecular weights of 2640 Da (PAMS-2640) and 6440 Da (PAMS-6440), respectively, at room temperature. At low pH, the decay of the hydroxycyclohexadienyl radical thus formed is accompanied by the formation of an absorption band in the visible region of the spectrum, which we tentatively assign to the radical cation of PAMS-2640 and -6440. The radical cation of PAMS-2640, formed by the reaction of SO4(˙-) with k = (6 ± 1) × 10(8) M(-1) s(-1), has a local absorption maximum at 560 nm, with ε560 ≥ 1400 M(-1) cm(-1). For the reaction of HO˙ and SO4(˙-) with the model compound benzenesulfonate, we measured k = (4-5) × 10(9) M(-1) s(-1) and (1.0 ± 0.3) × 10(8) M(-1) s(-1), respectively, while the reaction of SO4(˙-) with PAMS-6440 proceeds with (0.8-1) × 10(9) M(-1) s(-1). The 4-sulfophenoxyl radical was generated via the reaction of N3˙ with 4-hydroxybenzenesulfonate; ε410 ≥ 2300 M(-1) cm(-1). Not unexpectedly, the radical cation of PAMS is longer-lived than that of polystyrene sulfonic acid. Furthermore, fragmentation may result in desulfonation.
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Affiliation(s)
- Sindy M Dockheer
- Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology, Zurich, Switzerland
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18
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Sailer CF, Riedle E. Photogeneration and reactions of benzhydryl cations and radicals: A complex sequence of mechanisms from femtoseconds to microseconds. PURE APPL CHEM 2013. [DOI: 10.1351/pac-con-13-04-01] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Benzhydryl radicals and cations are reactive intermediates central to the
understanding of organic reactivity. They can be generated from benzhydryl
halides by UV irradiation. We performed transient absorption (TA) measurements
over the range from femtoseconds to microseconds to unravel the complete
reaction scheme. The 290–720-nm probe range allows the unambiguous monitoring of
all fragments. The appearance of the radical is delayed to the optical
excitation, the onset of the cation signal is found even later. Ab initio
calculations show that this non-rate behavior in the 100 fs range is due to
wavepacket motion from the Franck–Condon region to two distinct conical
intersections. The rise of the optical signal with a quasi-exponential time of
300 fs is assigned to the planarization and solvation of the photoproducts. The
bond cleavage predominantly generates radical pairs. A subsequent electron
transfer (ET) transforms radical pairs into ion pairs. Due to the broad
interradical distance distribution and the distance dependence, the ET is
strongly non-exponential. Part of the ion pairs recombine geminately. The ET and
the recombination are terminated by the depletion of close pairs and diffusional
separation. The remaining free radicals and cations undergo further reactions in
the nanosecond to microsecond regime.
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Affiliation(s)
- Christian F. Sailer
- 1Lehrstuhl für BioMolekulare Optik, Ludwig-Maximilians-Universität (LMU), München, Germany
| | - Eberhard Riedle
- 1Lehrstuhl für BioMolekulare Optik, Ludwig-Maximilians-Universität (LMU), München, Germany
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19
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Ammer J, Mayr H. Photogeneration of carbocations: applications in physical organic chemistry and the design of suitable precursors. J PHYS ORG CHEM 2013. [DOI: 10.1002/poc.3132] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Johannes Ammer
- Department Chemie; Ludwig-Maximilians-Universität München; Butenandtstrasse 5-13 (Haus F) 81377 München Germany
| | - Herbert Mayr
- Department Chemie; Ludwig-Maximilians-Universität München; Butenandtstrasse 5-13 (Haus F) 81377 München Germany
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20
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Hiratsuka H, Horiuchi H, Kudo T, Minegish T, Yonemoto A, Kusakari N, Okutsu T, Kamiyama N, Murakami S. Evidence for the Specific Species of Benzyltriethoxysilane Derivatives with a High-Coordination Silicon Atom. J Phys Chem A 2013; 117:4817-27. [DOI: 10.1021/jp308642z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hiroshi Hiratsuka
- Department of Chemistry and
Chemical Biology, and International Education and Research Center
for Silicon Science, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
| | - Hiroaki Horiuchi
- Department of Chemistry and
Chemical Biology, and International Education and Research Center
for Silicon Science, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
| | - Takako Kudo
- Department of Chemistry and
Chemical Biology, and International Education and Research Center
for Silicon Science, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
| | - Takeshi Minegish
- Department of Chemistry and
Chemical Biology, and International Education and Research Center
for Silicon Science, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
| | - Atsushi Yonemoto
- Department of Chemistry and
Chemical Biology, and International Education and Research Center
for Silicon Science, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
| | - Nobuharu Kusakari
- Department of Chemistry and
Chemical Biology, and International Education and Research Center
for Silicon Science, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
| | - Tetsuo Okutsu
- Department of Chemistry and
Chemical Biology, and International Education and Research Center
for Silicon Science, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
| | - Naoki Kamiyama
- Department of Chemistry and
Chemical Biology, and International Education and Research Center
for Silicon Science, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
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21
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Lang M, Holzmeier F, Fischer I, Hemberger P. Threshold Photoionization of Fluorenyl, Benzhydryl, Diphenylmethylene, and Their Dimers. J Phys Chem A 2013; 117:5260-8. [DOI: 10.1021/jp403158z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Melanie Lang
- Institute of Physical and Theoretical
Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Fabian Holzmeier
- Institute of Physical and Theoretical
Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Ingo Fischer
- Institute of Physical and Theoretical
Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Patrick Hemberger
- Molecular Dynamics Group, Paul Scherrer Institut (PSI), CH-5232 Villigen PSI,
Switzerland
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22
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Sailer CF, Thallmair S, Fingerhut BP, Nolte C, Ammer J, Mayr H, Pugliesi I, de Vivie-Riedle R, Riedle E. A Comprehensive Microscopic Picture of the Benzhydryl Radical and Cation Photogeneration and Interconversion through Electron Transfer. Chemphyschem 2013; 14:1423-37. [DOI: 10.1002/cphc.201201057] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Indexed: 11/09/2022]
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23
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Hallett-Tapley GL, D'Alfonso C, Pacioni NL, McTiernan CD, González-Béjar M, Lanzalunga O, Alarcon EI, Scaiano JC. Gold nanoparticle catalysis of the cis–trans isomerization of azobenzene. Chem Commun (Camb) 2013; 49:10073-5. [DOI: 10.1039/c3cc41669k] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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24
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Nigst TA, Ammer J, Mayr H. Photogeneration of benzhydryl cations by near-UV laser flash photolysis of pyridinium salts. J Phys Chem A 2012; 116:8494-9. [PMID: 22849534 DOI: 10.1021/jp3049247] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Laser flash irradiation of substituted N-benzhydryl pyridinium salts yields benzhydryl cations (diarylcarbenium ions) and/or benzhydryl radicals (diarylmethyl radicals). The use of 3,4,5-triamino-substituted pyridines as photoleaving groups allowed us to employ the third harmonic of a Nd/YAG laser (355 nm) for the photogeneration of benzhydryl cations. In this way, benzhydryl cations can also be photogenerated in the presence of aromatic compounds and in solvents which are opaque at the wavelength of the quadrupled Nd/YAG laser (266 nm). To demonstrate the scope and limitations of this method, the rate constants for the bimolecular reactions of benzhydryl cations with several substituted pyridines were determined in acetonitrile and with water in acetone. The obtained data agree with results obtained by stopped-flow UV-vis spectroscopic measurements. The rate constants for the reaction of the 4,4'-bis[methyl(2,2,2-trifluoroethyl)amino]benzhydrylium ion with 4-(dimethylamino)pyridine were also determined in dimethyl sulfoxide, N,N-dimethylformamide, and acetone. From the second-order rate constants, we derived the nucleophilicity parameters N and s(N) for the substituted pyridines, as defined by the linear free energy relationship, log k(2) = s(N)(N + E).
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Affiliation(s)
- Tobias A Nigst
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13 (Haus F), 81377 München, Germany
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25
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Ammer J, Nolte C, Mayr H. Free Energy Relationships for Reactions of Substituted Benzhydrylium Ions: From Enthalpy over Entropy to Diffusion Control. J Am Chem Soc 2012; 134:13902-11. [DOI: 10.1021/ja306522b] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Johannes Ammer
- Department
Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus F), 81377
München, Germany
| | - Christoph Nolte
- Department
Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus F), 81377
München, Germany
| | - Herbert Mayr
- Department
Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus F), 81377
München, Germany
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26
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Ammer J, Sailer CF, Riedle E, Mayr H. Photolytic Generation of Benzhydryl Cations and Radicals from Quaternary Phosphonium Salts: How Highly Reactive Carbocations Survive Their First Nanoseconds. J Am Chem Soc 2012; 134:11481-94. [DOI: 10.1021/ja3017522] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Johannes Ammer
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus F), 81377
München, Germany
| | - Christian F. Sailer
- Lehrstuhl für BioMolekulare
Optik, Ludwig-Maximilians-Universität München, Oettingenstrasse 67, 80538 München, Germany
| | - Eberhard Riedle
- Lehrstuhl für BioMolekulare
Optik, Ludwig-Maximilians-Universität München, Oettingenstrasse 67, 80538 München, Germany
| | - Herbert Mayr
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus F), 81377
München, Germany
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27
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Fingerhut BP, Sailer CF, Ammer J, Riedle E, de Vivie-Riedle R. Buildup and Decay of the Optical Absorption in the Ultrafast Photo-Generation and Reaction of Benzhydryl Cations in Solution. J Phys Chem A 2012; 116:11064-74. [DOI: 10.1021/jp300986t] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Benjamin P. Fingerhut
- Department Chemie, Ludwig-Maximilians-Universität (LMU), Butenandt-Strasse 11, 81377 München, Germany
| | - Christian F. Sailer
- Lehrstuhl für BioMolekulare
Optik, Ludwig-Maximilians-Universität (LMU), Oettingenstrasse 67, 80538 München, Germany
| | - Johannes Ammer
- Department Chemie, Ludwig-Maximilians-Universität (LMU), Butenandt-Strasse 11, 81377 München, Germany
| | - Eberhard Riedle
- Lehrstuhl für BioMolekulare
Optik, Ludwig-Maximilians-Universität (LMU), Oettingenstrasse 67, 80538 München, Germany
| | - Regina de Vivie-Riedle
- Department Chemie, Ludwig-Maximilians-Universität (LMU), Butenandt-Strasse 11, 81377 München, Germany
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29
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Encapsulation of diphenylmethyl phosphonium salts in reverse micelles: Enhanced bimolecular reaction of the photofragments. Chem Phys Lett 2011. [DOI: 10.1016/j.cplett.2011.06.087] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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30
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Mayr H, Patz M. Modelling carbocationic polymerizations: Kinetics of the reactions of carbocations with alkenes. ACTA ACUST UNITED AC 2011. [DOI: 10.1002/masy.19961070111] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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31
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Hallett-Tapley GL, Schepp NP, Cozens FL. The reactivity of diarylmethyl carbocations within non-protic zeolites. CAN J CHEM 2011. [DOI: 10.1139/v10-150] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The generation of diarylmethyl carbocations within non-protic zeolites (LiY, NaY, KY, RbY, CsY, and NaX) was carried out via laser excitation (266 nm or 266 nm / 308 nm) of diarylacetic acids. Rapid loss of CO2, followed by photochemical oxidation of the diarylmethyl radicals resulted in the formation of the diarylmethyl carbocations. The reactivity of the diarylmethyl carbocations was found to be highly dependent on the alkali metal counterion and the Si/Al ratio of the zeolite framework. Furthermore, the effect of various para-electron donating substituents (4-H, 3-CH3, 4-CH3, 4,4′-CH3, and 4-OCH3) on the diarylmethyl carbocation reactivity was investigated. Comparison of the Hammett plots constructed for the reactivity of the diarylmethyl carbocations in zeolites with those in solution (CH3CN–H2O (1:2) and TFE) showed decreased sensitivity of the electrophilic species towards para-electron donating substituents in the heterogeneous media. The leveling effect observed in the zeolite Hammett plots has been attributed to the presence of an isokinetic relationship, specifically, a low isokinetic temperature for the reaction of diarylmethyl carbocations with the aluminosilicate zeolite framework.
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Affiliation(s)
| | - Norman P. Schepp
- Department of Chemistry, Dalhousie University, Halifax, NS B3H 4J3, Canada
| | - Frances L. Cozens
- Department of Chemistry, Dalhousie University, Halifax, NS B3H 4J3, Canada
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32
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BANERJEE SANGHAMITRA, SAMANTA ANUNAY. Laser flash photolysis study on 9-phenylxanthenium tetrafluoroborate: Identification of new features due to the triplet state. J CHEM SCI 2011. [DOI: 10.1007/s12039-011-0070-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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33
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Ammer J, Baidya M, Kobayashi S, Mayr H. Nucleophilic reactivities of tertiary alkylamines. J PHYS ORG CHEM 2010. [DOI: 10.1002/poc.1707] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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34
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Ma C, Kwok W, An HY, Guan X, Fu M, Toy P, Phillips D. A Time-Resolved Spectroscopic Study of the Bichromophoric Phototrigger 3′,5′-Dimethoxybenzoin Diethyl Phosphate: Interaction Between the Two Chromophores Determines the Reaction Pathway. Chemistry 2010; 16:5102-18. [DOI: 10.1002/chem.200902891] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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35
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Ammer J, Mayr H. Electrophilic Reactivity of the α,α-Dimethylbenzyl (Cumyl) Cation. Macromolecules 2010. [DOI: 10.1021/ma9024569] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Johannes Ammer
- Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus F), 81377 München, Germany
| | - Herbert Mayr
- Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus F), 81377 München, Germany
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36
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Krumper JR, Salamant WA, Woerpel KA. Correlations between nucleophilicities and selectivities in the substitutions of tetrahydropyran acetals. J Org Chem 2010; 74:8039-50. [PMID: 19813702 DOI: 10.1021/jo901639b] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Selectivities that deviate from S(N)1 stereoelectronic models in the nucleophilic substitutions of tetrahydropyran acetals were investigated. When weak nucleophiles were employed, stereoselectivities conformed to known S(N)1 stereoelectronic models. In contrast, stereoselectivities in the substitutions of acetals with strong nucleophiles depended on reaction conditions. Erosions in selectivities were observed when strong nucleophiles were employed in the absence of coordinating counterions. These erosions in selectivities are attributed to rates of nucleophilic additions to oxocarbenium ion intermediates that approach the diffusion limit. When triflate counterions were present, however, S(N)2-like pathways became accessible with strong nucleophiles. In most cases examined, the major stereoisomers formed from reactions that proceeded through S(N)2-like pathways were opposite to the major stereoisomers formed from the analogous reactions that proceeded through S(N)1 pathways.
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Affiliation(s)
- Jennifer R Krumper
- Department of Chemistry, University of California, Irvine, California 92697-2025, USA
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37
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Stabilities and Reactivities of Carbocations. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2010. [DOI: 10.1016/s0065-3160(08)44002-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
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38
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Cao Q, Guan X, George MW, Phillips DL, Ma C, Kwok WM, Li M, Du Y, Sun XZ, Xue J. Ultrafast time-resolved transient infrared and resonance Raman spectroscopic study of the photo-deprotection and rearrangement reactions of p-hydroxyphenacyl caged phosphates. Faraday Discuss 2010. [DOI: 10.1039/b908188g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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39
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Abstract
Unsaturated benzyl cations (4-MeOC(6)H(4))CH(+)-(CH(2))(n)-CH=CH(2) (1) have been generated laser-flash photolytically in acetonitrile in the presence of enol ethers or 2-methylfuran. The reactions of the cations 1 (n=2 and 4) with these pi-nucleophiles follow second-order rate laws with rate constants comparable to those of the analogous saturated species (4-MeOC(6)H(4))CH(+)-(CH(2))(3)CH(3). Product studies show the absence of cyclization products. In contrast, the carbocation (4-MeOC(6)H(4))CH(+)-(CH(2))(3)-CH=CH(2) (1 d) undergoes a highly reversible 6-endo-trig cyclization which is approximately 10(7) times faster than the corresponding intermolecular reaction of (4-MeOC(6)H(4))CH(+)-(CH(2))(3)CH(3) with hex-1-ene. This cyclization yields a highly electrophilic, partially bridged carbocation, which accounts for the finding that 1 d is consumed eight times faster in trifluoroethanol solution than all other carbocations of this series. Quantum-chemical calculations (B3LYP/6-311G(d,p) and MP2/6-31+G(2d,p)) have been performed to elucidate the structures of the involved carbocations. Consequences of these findings on the role of pi-participation in solvolysis reactions are discussed.
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Affiliation(s)
- Lei Shi
- Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus F), 81377 München (Germany), Fax: (+49) 89-2180-77717
| | - Markus Horn
- Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus F), 81377 München (Germany), Fax: (+49) 89-2180-77717
| | - Shinjiro Kobayashi
- Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus F), 81377 München (Germany), Fax: (+49) 89-2180-77717
| | - Herbert Mayr
- Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus F), 81377 München (Germany), Fax: (+49) 89-2180-77717
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40
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Kanzian T, Nigst TA, Maier A, Pichl S, Mayr H. Nucleophilic Reactivities of Primary and Secondary Amines in Acetonitrile. European J Org Chem 2009. [DOI: 10.1002/ejoc.200900925] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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41
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Karakostas N, Naumov S, Brede O. Free Electron Transfer with Bifunctional Donors: p-Aminotritylsilanes. J Phys Chem A 2009; 113:14087-94. [DOI: 10.1021/jp9073569] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nikolaos Karakostas
- University of Leipzig, Wilhelm Ostwald Institute of Physical and Theoretical Chemistry, Linne’strasse 2, 04103 Leipzig, Germany, and Leibniz Institute of Surface Modification, Permoserstrasse 15, 04318 Leipzig, Germany
| | - Sergej Naumov
- University of Leipzig, Wilhelm Ostwald Institute of Physical and Theoretical Chemistry, Linne’strasse 2, 04103 Leipzig, Germany, and Leibniz Institute of Surface Modification, Permoserstrasse 15, 04318 Leipzig, Germany
| | - Ortwin Brede
- University of Leipzig, Wilhelm Ostwald Institute of Physical and Theoretical Chemistry, Linne’strasse 2, 04103 Leipzig, Germany, and Leibniz Institute of Surface Modification, Permoserstrasse 15, 04318 Leipzig, Germany
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42
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Okajima M, Soga K, Watanabe T, Terao K, Nokami T, Suga S, Yoshida JI. Generation of Diarylcarbenium Ion Pools via Electrochemical C–H Bond Dissociation. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2009. [DOI: 10.1246/bcsj.82.594] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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43
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Krumper JR, Salamant WA, Woerpel KA. Continuum of mechanisms for nucleophilic substitutions of cyclic acetals. Org Lett 2008; 10:4907-10. [PMID: 18844363 DOI: 10.1021/ol8019956] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effect of nucleophile strength on diastereoselectivity in the nucleophilic substitution of cyclic acetals was explored. Stereoselectivity remained constant and high as nucleophilicity increased until a threshold value was reached. Beyond this point, however, selection of Lewis acid determined whether stereochemical inversion or erosion was observed.
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Affiliation(s)
- Jennifer R Krumper
- Department of Chemistry, University of California, Irvine, California 92697-2025, USA
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Baciocchi E, Del Giacco T, Lanzalunga O, Mencarelli P, Procacci B. Photosensitized Oxidation of Alkyl Phenyl Sulfoxides. C−S Bond Cleavage in Alkyl Phenyl Sulfoxide Radical Cations. J Org Chem 2008; 73:5675-82. [DOI: 10.1021/jo801088n] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Enrico Baciocchi
- Dipartimento di Chimica and Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione c/o Dipartimento di Chimica, Sapienza Università di Roma, P.le A. Moro 5, 00185 Rome, Italy, and Dipartimento di Chimica and Centro di Eccellenza Materiali Innovativi Nanostrutturati, Università di Perugia, via Elce di sotto 8, 06123 Perugia, Italy
| | - Tiziana Del Giacco
- Dipartimento di Chimica and Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione c/o Dipartimento di Chimica, Sapienza Università di Roma, P.le A. Moro 5, 00185 Rome, Italy, and Dipartimento di Chimica and Centro di Eccellenza Materiali Innovativi Nanostrutturati, Università di Perugia, via Elce di sotto 8, 06123 Perugia, Italy
| | - Osvaldo Lanzalunga
- Dipartimento di Chimica and Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione c/o Dipartimento di Chimica, Sapienza Università di Roma, P.le A. Moro 5, 00185 Rome, Italy, and Dipartimento di Chimica and Centro di Eccellenza Materiali Innovativi Nanostrutturati, Università di Perugia, via Elce di sotto 8, 06123 Perugia, Italy
| | - Paolo Mencarelli
- Dipartimento di Chimica and Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione c/o Dipartimento di Chimica, Sapienza Università di Roma, P.le A. Moro 5, 00185 Rome, Italy, and Dipartimento di Chimica and Centro di Eccellenza Materiali Innovativi Nanostrutturati, Università di Perugia, via Elce di sotto 8, 06123 Perugia, Italy
| | - Barbara Procacci
- Dipartimento di Chimica and Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione c/o Dipartimento di Chimica, Sapienza Università di Roma, P.le A. Moro 5, 00185 Rome, Italy, and Dipartimento di Chimica and Centro di Eccellenza Materiali Innovativi Nanostrutturati, Università di Perugia, via Elce di sotto 8, 06123 Perugia, Italy
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45
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Diao L, Wan P. Chemistry of photogenerated α-phenyl-substituted o-, m-, and p-quinone methides from phenol derivatives in aqueous solution. CAN J CHEM 2008. [DOI: 10.1139/v07-125] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The enhanced photochemical reactivity of o-substituted phenols in its propensity to give o-quinone methide (o-QM) intermediates via excited state intramolecular proton transfer (ESIPT) was uncovered by Keith Yates as part of his now classic studies of photohydration of aromatic alkenes, alkynes, and related compounds. Photogeneration of QMs and the study of their chemistry along with potential biological applications are the focus of many groups. In this work, photochemical precursors to o-, m-, and p-QMs based on substituted phenols (hydroxybenzyl alcohols) and related compounds have been studied in aqueous solution as a function of pH and water content. The focus will be on QMs that are stabilized by an α-phenyl substituent, which enhances quantum yields for their formation, with the resulting QMs having longer lifetimes and easier to detect. Noteworthy is that all QM isomers can be photogenerated with the o and m isomers being the most efficient, consistent with the Zimmerman “ortho-meta” effect. m-QMs have formal non-Kekulé structures, and although they can be routinely photogenerated, are found to be most reactive. One m-QM was found to undergo a photocondensation reaction at high pH giving rise to m-substituted oligomers. The mechanism of QM formation in aqueous solution is believed to involve singlet excited phenols that undergo adiabatic deprotonation to give the corresponding photoexcited phenolate ion, which subsequently expels the hydroxide ion (photodehydroxylation). A pathway involving direct loss of water for the o-isomers is also possible in organic solvents.Key words: quinone methides, phenols, excited state acidity, solvolysis, carbocations, meta effect, photopolymerization, non-Kekulé intermediates.
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46
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Heeb LR, Peters KS. Picosecond Kinetic Study of the Photoinduced Homolysis of Benzhydryl Acetates: The Nature of the Conversion of Radical Pairs into Ion Pairs. J Am Chem Soc 2008; 130:1711-7. [DOI: 10.1021/ja077105n] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Libby R. Heeb
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309
| | - Kevin S. Peters
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309
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47
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Fingerhut BP, Geppert D, de Vivie-Riedle R. Ultrafast dissociation pathways of diphenylmethyl chloride to generate reactive carbo cations. Chem Phys 2008. [DOI: 10.1016/j.chemphys.2007.07.034] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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48
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Del Giacco T, Faltoni A, Elisei F. Anomalous reactivity of radical cations produced by photosensitized oxidation of 4-methoxybenzyl alcohol derivatives: role of the sensitizer. Phys Chem Chem Phys 2008; 10:200-10. [DOI: 10.1039/b711541e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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49
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Peters KS. Nature of Dynamic Processes Associated with the SN1 Reaction Mechanism. Chem Rev 2007; 107:859-73. [PMID: 17319730 DOI: 10.1021/cr068021k] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Kevin S Peters
- Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, Colorado 80309-0215, USA
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50
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Gross CL, Girolami GS. Synthesis and NMR Studies of [(C5Me5)Os(L)H2(H2)+] Complexes. Evidence of the Adoption of Different Structures by a Dihydrogen Complex in Solution and the Solid State. Organometallics 2007. [DOI: 10.1021/om061017e] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Christopher L. Gross
- The School of Chemical Sciences, The University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801
| | - Gregory S. Girolami
- The School of Chemical Sciences, The University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801
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