1
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Rap DB, Simon A, Steenbakkers K, Schrauwen JGM, Redlich B, Brünken S. Fingerprinting fragments of fragile interstellar molecules: dissociation chemistry of pyridine and benzonitrile revealed by infrared spectroscopy and theory. Faraday Discuss 2023; 245:221-244. [PMID: 37404008 PMCID: PMC10510038 DOI: 10.1039/d3fd00015j] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 03/22/2023] [Indexed: 07/06/2023]
Abstract
The cationic fragmentation products in the dissociative ionization of pyridine and benzonitrile have been studied by infrared action spectroscopy in a cryogenic ion trap instrument at the Free-Electron Lasers for Infrared eXperiments (FELIX) Laboratory. A comparison of the experimental vibrational fingerprints of the dominant cationic fragments with those from quantum chemical calculations revealed a diversity of molecular fragment structures. The loss of HCN/HNC is shown to be the major fragmentation channel for both pyridine and benzonitrile. Using the determined structures of the cationic fragments, potential energy surfaces have been calculated to elucidate the nature of the neutral fragment partner. In the fragmentation chemistry of pyridine, multiple non-cyclic structures are formed, whereas the fragmentation of benzonitrile dominantly leads to the formation of cyclic structures. Among the fragments are linear cyano-(di)acetylene˙+, methylene-cyclopropene˙+ and o- and m-benzyne˙+ structures, the latter possible building blocks in interstellar polycyclic aromatic hydrocarbon (PAH) formation chemistry. Molecular dynamics simulations using density functional based tight binding (MD/DFTB) were performed and used to benchmark and elucidate the different fragmentation pathways based on the experimentally determined structures. The implications of the difference in fragments observed for pyridine and benzonitrile are discussed in an astrochemical context.
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Affiliation(s)
- Daniël B Rap
- Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
| | - Aude Simon
- Laboratoire de Chimie et Physique Quantiques (LCPQ), Fédération FeRMI, CNRS & Université Toulouse III - Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse, France
| | - Kim Steenbakkers
- Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
| | - Johanna G M Schrauwen
- Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
| | - Britta Redlich
- Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
| | - Sandra Brünken
- Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
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2
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Fischer I, Hemberger P. Photoelectron Photoion Coincidence Spectroscopy of Biradicals. Chemphyschem 2023; 24:e202300334. [PMID: 37325876 DOI: 10.1002/cphc.202300334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 06/15/2023] [Accepted: 06/15/2023] [Indexed: 06/17/2023]
Abstract
The electronic structure of biradicals is characterized by the presence of two unpaired electrons in degenerate or near-degenerate molecular orbitals. In particular, some of the most relevant species are highly reactive, difficult to generate cleanly and can only be studied in the gas phase or in matrices. Unveiling their electronic structure is, however, of paramount interest to understand their chemistry. Photoelectron photoion coincidence (PEPICO) spectroscopy is an excellent approach to explore the electronic states of biradicals, because it enables a direct correlation between the detected ions and electrons. This permits to extract unique vibrationally resolved photoion mass-selected threshold photoelectron spectra (ms-TPES) to obtain insight in the electronic structure of both the neutral and the cation. In this review we highlight most recent advances on the spectroscopy of biradicals and biradicaloids, utilizing PEPICO spectroscopy and vacuum ultraviolet (VUV) synchrotron radiation.
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Affiliation(s)
- Ingo Fischer
- Julius-Maximilians-Universität Würzburg, Institut für Physikalische und Theoretische Chemie, Am Hubland, D-97074, Würzburg, Germany
| | - Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institut (PSI), CH-5232, Villigen, Switzerland
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3
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Li Q, Hua Y, Tang C, Chen D, Luo M, Xia H. Isolation, Reactivity, and Tunable Properties of a Strained Antiaromatic Osmacycle. J Am Chem Soc 2023; 145:7580-7591. [PMID: 36952602 DOI: 10.1021/jacs.3c00942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/25/2023]
Abstract
Strain and antiaromaticity in compounds are recognized as two substantial destabilizing features, and consequently, realization of dual destabilizing features in a single molecule is challenging and far more difficult in a single ring. Moreover, transformation of an antiaromatic framework to different antiaromatic or aromatic species is a significant subject in antiaromatic chemistry and has attracted increasing interest. In this work, we isolated a highly strained antiaromatic metallacycle in which a cyclic metal vinylidene unit is embedded. Computational studies revealed its ring strain energies and antiaromatic character and showed that the metal incorporation and the phosphonium substituents play a crucial role in its stabilization. The mechanism of its formation has been illustrated by density functional theory (DFT) calculations and the isolation of a key intermediate. We further discovered diverse reactivities and structural reshuffling of this unusual strained antiaromatic complex according to its two destabilizing characters. We obtained two isomers of metallaindenes fused with oxiranes from the direct oxidation of the metal vinylidene or by nucleophilic addition to an isolated metallacyclocumulene formed by the reaction of metal vinylidene with hydroxide ion, achieving a reconfiguration of the antiaromatic framework. Transformations of the antiaromatic metallacycle by electrophiles to various aromatic metallaindynes have been achieved, and that a condensed Fukui function was employed to confirm the regioselectivity of the electrophilic additions, and the acid/base-induced aromaticity switch along with tunable photophysical properties were investigated. These interesting transformations not only enrich the chemistry of metal vinylidenes and antiaromatics and could also perform potentially as switchable optical materials.
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Affiliation(s)
- Qian Li
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
| | - Yuhui Hua
- Shenzhen Grubbs Institute, Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, P. R. China
| | - Chun Tang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
| | - Dafa Chen
- Shenzhen Grubbs Institute, Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, P. R. China
| | - Ming Luo
- Shenzhen Grubbs Institute, Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, P. R. China
| | - Haiping Xia
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
- Shenzhen Grubbs Institute, Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, P. R. China
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4
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Gerlach M, Karaev E, Schaffner D, Hemberger P, Fischer I. Threshold Photoelectron Spectrum of m-Benzyne. J Phys Chem Lett 2022; 13:11295-11299. [PMID: 36449562 DOI: 10.1021/acs.jpclett.2c03216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Due to their unusual electronic structure, the biradical m-benzyne, C6H4, and its cation are of considerable interest in chemistry. Here, the photoion mass-selected threshold photoelectron spectrum of the m-benzyne biradical is presented. An adiabatic ionization energy of 8.65 ± 0.015 eV is derived, while a vibrational progression of 0.10 eV is assigned to the ν9+ ring breathing mode, in excellent agreement with computations. The experimental spectrum was reproduced well by Franck-Condon spectral modeling of the 2A1 ← X 1A1 transition, in which the cation retains a monocyclic C6 framework. The energetically close-lying bicyclic 2A2 cation state exhibits low Franck-Condon factors, due to the large change in geometry, and thus cannot be observed.
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Affiliation(s)
- M Gerlach
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - E Karaev
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - D Schaffner
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - P Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institut (PSI), CH-5232 Villigen-PSI, Switzerland
| | - I Fischer
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
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5
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Gutowski Ł, Liszewska M, Bartosewicz B, Budner B, Weyher JL, Jankiewicz BJ. Investigation of organic monoradicals reactivity using surface-enhanced Raman spectroscopy. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 278:121312. [PMID: 35537259 DOI: 10.1016/j.saa.2022.121312] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 03/28/2022] [Accepted: 04/23/2022] [Indexed: 06/14/2023]
Abstract
Surface-enhanced Raman spectroscopy (SERS) and self-assembled monolayer (SAM) approaches were used to investigate the reactions of organic monoradicals with methanol. An attempt was made to generate monoradicals from thiophenols and phenylmethanethiols substituted with bromine, iodine, and nitro groups by irradiation with UV light. Monolayers of radical precursors were deposited on SERS substrates, which were then immersed in methanol and irradiated for 1 and/or 3, 6, 12 and 24 h in a UV photochemical reactor. Pre- and postreaction SERS spectra were obtained by using a confocal Raman microscope and compared with the spectra of expected products of the radical reaction with methanol. Our studies have shown that the efficiency of monoradical generation is highly dependent on the chemical structure of the precursor. In addition, it is shown that both the SERS substrate and experimental conditions used strongly influence the obtained results.
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Affiliation(s)
- Łukasz Gutowski
- Institute of Optoelectronics, Military University of Technology, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland.
| | - Malwina Liszewska
- Institute of Optoelectronics, Military University of Technology, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland.
| | - Bartosz Bartosewicz
- Institute of Optoelectronics, Military University of Technology, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland.
| | - Bogusław Budner
- Institute of Optoelectronics, Military University of Technology, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland.
| | - Jan L Weyher
- Institute of High-Pressure Physics, Polish Academy of Sciences, Sokołowska 29/37, 01-142 Warsaw, Poland.
| | - Bartłomiej J Jankiewicz
- Institute of Optoelectronics, Military University of Technology, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland.
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6
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Lewars E. Another possible planar tetracoordinate carbon saturated hydrocarbon, a computational study. CAN J CHEM 2019. [DOI: 10.1139/cjc-2018-0315] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Building on earlier computational work by Radom and Rasmussen, the author found a smaller candidate (C17H16) for a hydrocarbon with a planar tetracoordinate carbon atom than the candidate (C23H24) that had been reported by those workers. This molecule is apparently very unstable but nevertheless significant because it may be the smallest neutral hydrocarbon with such a carbon atom and its smaller size makes it easier to study at high computational levels.
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Affiliation(s)
- Errol Lewars
- Department of Chemistry, Trent University, Peterborough, ON K9J 7B8, Canada
- Department of Chemistry, Trent University, Peterborough, ON K9J 7B8, Canada
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7
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Luo S, Kuhn AJ, Castano I, Castro C, Karney WL. Hydrogen Shifts in Aryl Radicals and Diradicals: The Role of m-Benzynes. J Org Chem 2018; 83:314-322. [PMID: 29224344 DOI: 10.1021/acs.joc.7b02724] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Density functional and coupled cluster results are presented for hydrogen shifts in radicals derived from polycyclic aromatic hydrocarbons (PAHs) and for rearrangement mechanisms for several phenylenes. RCCSD(T)/cc-pVDZ//UBLYP/cc-pVDZ free energy barriers for 1,4-H shifts at 298 K are consistently predicted to be ca. 25 kcal/mol, whereas barriers for 1,5- and 1,6-shifts range from 6 to 28 kcal/mol. The barriers correlate reasonably well with the distance from the radical center to the shifting hydrogen in the reactant. Proposed mechanisms (via diradical intermediates) of known rearrangements of linear [3]phenylene, benzo[b]biphenylene, and angular [4]phenylene have BD(T)/cc-pVDZ//(U)BLYP/cc-pVDZ computed barriers of 74-82 kcal/mol, consistent with pyrolysis temperatures of 900 to 1100 °C. Hydrogen shift reactions in most of the aryl diradicals arising from phenylenes produce m-benzyne intermediates which, despite being 8-15 kcal/mol more stable than other diradicals involved in the pathways, do not significantly lower the computed overall free energies of activation.
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Affiliation(s)
- Simon Luo
- Department of Chemistry and ‡Department of Environmental Science, University of San Francisco , 2130 Fulton Street, San Francisco, California 94117, United States
| | - Ariel J Kuhn
- Department of Chemistry and ‡Department of Environmental Science, University of San Francisco , 2130 Fulton Street, San Francisco, California 94117, United States
| | - Ioannina Castano
- Department of Chemistry and ‡Department of Environmental Science, University of San Francisco , 2130 Fulton Street, San Francisco, California 94117, United States
| | - Claire Castro
- Department of Chemistry and ‡Department of Environmental Science, University of San Francisco , 2130 Fulton Street, San Francisco, California 94117, United States
| | - William L Karney
- Department of Chemistry and ‡Department of Environmental Science, University of San Francisco , 2130 Fulton Street, San Francisco, California 94117, United States
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8
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Pavliček N, Majzik Z, Collazos S, Meyer G, Pérez D, Guitián E, Peña D, Gross L. Generation and Characterization of a meta-Aryne on Cu and NaCl Surfaces. ACS NANO 2017; 11:10768-10773. [PMID: 29028295 DOI: 10.1021/acsnano.7b06137] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We describe the generation of a meta-aryne at low temperature (T = 5 K) using atomic manipulation on Cu(111) and on bilayer NaCl on Cu(111). We observe different voltage thresholds for dehalogenation of the precursor and different reaction products depending on the substrate surface. The chemical structure is resolved by atomic force microscopy with CO-terminated tips, revealing the radical positions and confirming a diradical rather than an anti-Bredt olefin structure for this meta-aryne on NaCl.
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Affiliation(s)
- Niko Pavliček
- IBM Research-Zurich , Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Zsolt Majzik
- IBM Research-Zurich , Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Sara Collazos
- CIQUS, Universidade de Santiagode Compostela , 15782 Santiago de Compostela, Spain
| | - Gerhard Meyer
- IBM Research-Zurich , Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Dolores Pérez
- CIQUS, Universidade de Santiagode Compostela , 15782 Santiago de Compostela, Spain
| | - Enrique Guitián
- CIQUS, Universidade de Santiagode Compostela , 15782 Santiago de Compostela, Spain
| | - Diego Peña
- CIQUS, Universidade de Santiagode Compostela , 15782 Santiago de Compostela, Spain
| | - Leo Gross
- IBM Research-Zurich , Säumerstrasse 4, 8803 Rüschlikon, Switzerland
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9
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Affiliation(s)
- Curt Wentrup
- School of Chemistry and Molecular Biosciences The University of Queensland Brisbane Qld 4072 Australien
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10
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Wentrup C. Flash Vacuum Pyrolysis: Techniques and Reactions. Angew Chem Int Ed Engl 2017; 56:14808-14835. [PMID: 28675675 DOI: 10.1002/anie.201705118] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Indexed: 12/13/2022]
Abstract
Flash vacuum pyrolysis (FVP) had its beginnings in the 1940s and 1950s, mainly through mass spectrometric detection of pyrolytically formed free radicals. In the 1960s many organic chemists started performing FVP experiments with the purpose of isolating new and interesting compounds and understanding pyrolysis processes. Meanwhile, many different types of apparatus and techniques have been developed, and it is the purpose of this review to present the most important methods as well as a survey of typical reactions and observations that can be achieved with the various techniques. This includes preparative FVP, chemical trapping reactions, matrix isolation, and low temperature spectroscopy of reactive intermediates and unstable molecules, the use of online mass, photoelectron, microwave, and millimeterwave spectroscopies, gas-phase laser pyrolysis, pulsed pyrolysis with supersonic jet expansion, very low pressure pyrolysis for kinetic investigations, solution-spray and falling-solid FVP for involatile compounds, and pyrolysis over solid supports and reagents. Moreover, the combination of FVP with matrix isolation and photochemistry is a powerful tool for investigations of reaction mechanism.
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Affiliation(s)
- Curt Wentrup
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld, 4072, Australia
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11
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Sah C, Jacob L, Saraswat M, Venkataramani S. Does a Nitrogen Lone Pair Lead to Two Centered-Three Electron (2c-3e) Interactions in Pyridyl Radical Isomers? J Phys Chem A 2017; 121:3781-3791. [PMID: 28423280 DOI: 10.1021/acs.jpca.7b01501] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Each of the three isomeric pyridyl radicals (2-, 3-, and 4-dehydropyridines) contains a lone pair and an unpaired electron. As a result, a potential two centered-three electron interaction between the radical electron and the lone pair through-space (TS) and/or through-bond (TB) can exist that may influence the stability of the radicals. Due to the change in geometrical positions relative to each other, the strength of interaction can be varied. In this study, we investigated the structural and stability aspects of pyridyl radical isomers with a major emphasis on the interaction of a nitrogen lone pair with the radical center. In order to obtain evidence for such interactions, protonated and N-oxide analogues of the corresponding isomeric pyridyl radicals have been considered in such a way to understand the consequences due to unavailability of the lone pair. Similarly, electron attachment and detachment energies at the radical center (vertical detachment energy, VDE, of corresponding anions and vertical ionization energy, VIE, of radical isomers) have been calculated to find out the interaction trend upon modification at the radical center. Different levels of theory including (U)B3LYP/cc-pVTZ, (U)M06/cc-pVTZ, CBS-QB3, single-point energy calculations at (U)CCSD(T)/cc-pVTZ, and multireference CASSCF/cc-pVTZ methods have been employed in this regard. A closer inspection of geometries, relative stability order, spin density, electrostatic potential, molecular orbitals, NBO analysis, and vibrational analysis have showed a strong and stabilizing TS interaction between the radical center and the lone pair in the case of the 2-pyridyl radical. On the other hand, the 4-pyridyl radical showed stabilizing interactions only via TB coupling, whereas the TS interaction is nonexistent. Despite the presence of both interactions in the case of the 3-pyridyl radical, their overall influence is less effective toward stability.
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Affiliation(s)
- Chitranjan Sah
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali , Sector 81, SAS Nagar, Knowledge City, Mohali, Punjab 140306, India
| | - Lilit Jacob
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali , Sector 81, SAS Nagar, Knowledge City, Mohali, Punjab 140306, India
| | - Mayank Saraswat
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali , Sector 81, SAS Nagar, Knowledge City, Mohali, Punjab 140306, India
| | - Sugumar Venkataramani
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali , Sector 81, SAS Nagar, Knowledge City, Mohali, Punjab 140306, India
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12
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Simic-Milosevic V, Mehlhorn M, Morgenstern K. Imaging the Bonds of Dehalogenated Benzene Radicals on Cu(111) and Au(111). Chemphyschem 2016; 17:2679-85. [PMID: 27272737 DOI: 10.1002/cphc.201600495] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Indexed: 11/07/2022]
Abstract
Dissociative adsorption of doubly substituted benzene molecules leads to formation of benzyne radicals. In this study, co-adsorbed hydrogen molecules are used in scanning tunneling hydrogen microscopy to enhance the contrast of the meta- and the para-isomers of these radicals on Cu(111) and Au(111). Up to three hydrogen molecules are attached to one radical. One hydrogen molecule reveals the orientation of the carbon ring and its adsorption site, allowing discrimination between the two radicals. Two hydrogen molecules reflect the bond picture of the carbon skeleton and reveals that adsorption on Cu(111) distorts the meta- isomer differently from its gas-phase distortion. Three hydrogen molecules allow us to determine the bond picture of a minor species.
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Affiliation(s)
| | - Michael Mehlhorn
- Institut für Experimentalphysik, FU Berlin, Arnimallee 14, D-14195, Berlin, Germany
| | - Karina Morgenstern
- Institut für Experimentalphysik, FU Berlin, Arnimallee 14, D-14195, Berlin, Germany. .,Ruhr-Universität Bochum, Lehrstuhl für Physikalische Chemie I, D-44780, Bochum, Germany.
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13
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Sinha Ray S, Ghosh A, Chattopadhyay S, Chaudhuri RK. Taming the Electronic Structure of Diradicals through the Window of Computationally Cost Effective Multireference Perturbation Theory. J Phys Chem A 2016; 120:5897-916. [DOI: 10.1021/acs.jpca.6b03211] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Suvonil Sinha Ray
- Department of Chemistry, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103, India
| | - Anirban Ghosh
- Department of Chemistry, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103, India
| | - Sudip Chattopadhyay
- Department of Chemistry, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103, India
| | - Rajat K. Chaudhuri
- Theoretical Physics, Indian Institute of Astrophysics, Bangalore 560034, India
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14
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Evaluation of modern DFT functionals and G3n-RAD composite methods in the modelization of organic singlet diradicals. J Mol Model 2016; 22:76. [DOI: 10.1007/s00894-016-2950-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 02/29/2016] [Indexed: 11/26/2022]
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15
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Ito S. Chain-growth polymerization enabling formation/introduction of arylene groups into polymer main chains. Polym J 2016. [DOI: 10.1038/pj.2016.18] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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16
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Edel K, Fink RF, Bettinger HF. Isomerization and fragmentation pathways of 1,2-azaborine. J Comput Chem 2015; 37:110-6. [PMID: 26418051 DOI: 10.1002/jcc.24189] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 07/28/2015] [Accepted: 07/30/2015] [Indexed: 11/11/2022]
Abstract
The generation of 1,2-azaborine (4), the BN-analogue of ortho-benzyne, was recently achieved by elimination of tert-butyldimethylchlorosilane under the conditions of flash vacuum pyrolysis. The present investigation identifies by computational means pathways for the thermal isomerization and fragmentation of 1,2-azaborine. The computations were performed using single reference (hybrid/density functional, second order Møller-Plesset perturbation, and coupled cluster theories) as well as multiconfiguration methods (complete active space SCF based second order perturbation theory, multireference configuration interaction, and multiconfiguration coupled electron pair approximation) with basis sets up to polarized triple-ζ quality. The 1,2-azaborine is, despite the distortion of its molecular structure, the most stable C4H4BN isomer investigated. The formation of BN-endiyne isomers is highly unfavorable as the identified pathways involve barriers close to 80 kcal mol(-1). The concerted fragmentation to ethyne and 2-aza-3-bora-butadiyne even has a barrier close to 120 kcal mol(-1). The fragmentation of BN-enediynes has energetic requirements similar to enediynes.
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Affiliation(s)
- Klara Edel
- Institut Für Organische Chemie, Universität Tübingen, Auf Der Morgenstelle 18, Tübingen, 72076, Germany
| | - Reinhold F Fink
- Institut Für Physikalische Und Theoretische Chemie, Universität Tübingen, Auf Der Morgenstelle 18, Tübingen, 72076, Germany
| | - Holger F Bettinger
- Institut Für Organische Chemie, Universität Tübingen, Auf Der Morgenstelle 18, Tübingen, 72076, Germany
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17
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Toh SY, Djuricanin P, Momose T, Miyazaki J. UV Photochemistry of Benzene and Cyclohexadienyl Radical in Solid Parahydrogen. J Phys Chem A 2015; 119:2683-91. [DOI: 10.1021/jp5098537] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shin Yi Toh
- Department
of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
| | - Pavle Djuricanin
- Department
of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
| | - Takamasa Momose
- Department
of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
| | - Jun Miyazaki
- Department
of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
- Department
of Liberal Arts and Basic Sciences, College of Industrial Technology, Nihon University, 2-11-1 Shinei, Narashino, Chiba 275-8576, Japan
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18
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Garza AJ, Jiménez-Hoyos CA, Scuseria GE. Electronic correlation without double counting via a combination of spin projected Hartree-Fock and density functional theories. J Chem Phys 2014; 140:244102. [DOI: 10.1063/1.4883491] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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19
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Schutski R, Jiménez-Hoyos CA, Scuseria GE. Analytic energy gradient for the projected Hartree–Fock method. J Chem Phys 2014; 140:204101. [DOI: 10.1063/1.4876490] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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20
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Hatua K, Nandi PK. Third-order NLO property of beryllium-pyridyne complexes. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2014. [DOI: 10.1142/s0219633613500752] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Six pyridyne isomers and their complexes with beryllium have been considered for the theoretical study of the third-order polarizability. The NLO properties are calculated by employing the DFT functionals BLYP, B3LYP, BHHLYP, B3PW91, BP86 and B2PLYP for the 6-311++G(d,p) basis set. The C - Be bond length in the complexes varies within 1.644 Å–1.771 Å indicating covalent interactions between the metal and pyridynes. The present investigation reveals that the magnitude of second-hyperpolarizability of pyridynes strongly enhances upon complex formation with beryllium. The maximum hyperpolarizability has been predicted for the 2,5-diberyllium pyridine complex. The lowest value of hyperpolarizability is obtained for the 2,3- and 3,4-diberyllium pyridine complexes. The chosen DFT methods predict almost identical pattern of variation of NLO property. The variation of second-hyperpolarizability has been satisfactorily explained by the excitation energy and transition dipole moment associated with the most dominant excited state.
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Affiliation(s)
- Kaushik Hatua
- Department of Chemistry, Bengal Engineering and Science University, Shibpur, Howrah 711 103, India
| | - Prasanta K. Nandi
- Department of Chemistry, Bengal Engineering and Science University, Shibpur, Howrah 711 103, India
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21
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Abstract
Consistent with the definition of diradicals, triradicals arespecies in which three electrons occupy three (nearly) degenerate orbitals, resulting in close-lying quartet and doublet states. The same concepts and rules that can be used to predict and rationalize the ground state multiplicity of diradicals also apply to triradicals, but the greater number of states in triradicals generally leads to more complex electronic structures. Most experimentally accessible triradicals are based onorganic π-systems; therefore triradicals are classified according to the σ/π symmetry of the nominally nonbonding molecular orbitals (NBMOs). The tridehydrobenzenes are prototypal σσσ triradicals with doublet ground states and significant doublet-quartet energy splittings. In all three isomers, the ordering of electronic states depends critically on the distance between the m-radical centers, which makes computational studies of these systems demanding. The experimental IR spectrum of matrix-isolated 1,2,3-tridehydrobenzene led to a revision of the previous ground state assignment based on computations. This work demonstrates the close interplay between experiment and theory in this realm of reactive intermediate chemistry. 1,3,5-Tridehydrobenzene can be isolated as its trifluoro derivative. The stabilization of dehydrophenyl nitrenes, typical members of the σσπ family of triradicals, also requires ortho-fluorination. Because of their quartet ground states, derivatives of 2-dehydrophenyl nitrene and 4-dehydrophenyl nitrene could be studied using IR or EPR spectroscopy. The zero-field splitting parameters of these systems provide direct evidence for the contribution of carbenoid resonance structures to the resonance hybrid of the high-spin systems. According to computations, the through-bond coupling of the in-plane electrons thermodynamically stabilizes the doublet ground states of m-dehydrophenyl nitrenes. But for the same reasons, these systems are prone to ring-opening reactions, which make them difficult to isolate. Remarkably, the m-phenylene unit leads to strongly antiferromagnetic coupling in σσπ triradicals, while o- or p-coupling results in high-spin systems. The more common all-π systems show the opposite pattern because the latter connectivity naturally results in closed-shell arrangements. Within the family of σππ triradicals, we could characterize 2-dehydro-m-xylylene and 4-dehydro-m-xylylene by EPR spectroscopy, whereas the 5-isomer features a doublet ground state. This observation is readily rationalized considering the nodal characteristics of the NBMOs involved and by simple spin polarization models. 1,3,5-Trimethylenebenzene strongly prefers ferromagnetic coupling and features a robust quartet ground state. We have synthesized this πππ triradical in cryogenic matrices and characterized it by IR and EPR spectroscopy. Interestingly, the triradical is photochemically much more stable than m-xylylene, a diradical that shows fascinating rearrangements upon irradiation in cryogenic matrices.
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Affiliation(s)
- Michael Winkler
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
| | - Wolfram Sander
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
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22
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Gao J, Jankiewicz BJ, Reece J, Sheng H, Cramer CJ, Nash JJ, Kenttämaa HI. On the factors that control the reactivity of meta-benzynes. Chem Sci 2014. [DOI: 10.1039/c4sc00194j] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The key reactivity controlling parameters of meta-benzynes have been identified and demonstrated to have a major influence on their reactivity.
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Affiliation(s)
- Jinshan Gao
- Department of Chemistry
- Purdue University
- West Lafayette, USA
| | | | - Jennifer Reece
- Department of Chemistry
- Purdue University
- West Lafayette, USA
| | - Huaming Sheng
- Department of Chemistry
- Purdue University
- West Lafayette, USA
| | - Christopher J. Cramer
- Department of Chemistry
- Chemical Theory Center and Supercomputing Institute
- University of Minnesota
- Minneapolis, USA
| | - John J. Nash
- Department of Chemistry
- Purdue University
- West Lafayette, USA
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23
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Ghigo G, Maranzana A, Tonachini G. o-Benzyne fragmentation and isomerization pathways: a CASPT2 study. Phys Chem Chem Phys 2014; 16:23944-51. [DOI: 10.1039/c4cp02582b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The mechanism for the thermal fragmentation of o-benzyne to C4H2 + C2H2 and C6H2.
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Affiliation(s)
- Giovanni Ghigo
- Dipartimento di Chimica
- Università di Torino
- 10125 Torino, Italy
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24
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Fulara J, Nagy A, Filipkowski K, Thimmakondu VS, Stanton JF, Maier JP. Electronic Transitions of C6H4+ Isomers: Neon Matrix and Theoretical Studies. J Phys Chem A 2013; 117:13605-15. [DOI: 10.1021/jp407566h] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jan Fulara
- Department
of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | - Adam Nagy
- Department
of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | - Karol Filipkowski
- Department
of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | - Venkatesan S. Thimmakondu
- Department
of Chemistry and Biochemistry, The University of Texas at Austin, 1
University Station A5300, Austin, Texas 78712-0165, United States
| | - John F. Stanton
- Department
of Chemistry and Biochemistry, The University of Texas at Austin, 1
University Station A5300, Austin, Texas 78712-0165, United States
| | - John P. Maier
- Department
of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
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25
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Kraka E, Cremer D. Enediynes, enyne-allenes, their reactions, and beyond. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2013. [DOI: 10.1002/wcms.1174] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Elfi Kraka
- Computational and Theoretical Chemistry Group, Department of Chemistry; Southern Methodist University; Dallas TX USA
| | - Dieter Cremer
- Computational and Theoretical Chemistry Group, Department of Chemistry; Southern Methodist University; Dallas TX USA
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26
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Williams PE, Jankiewicz BJ, Yang L, Kenttämaa HI. Properties and reactivity of gaseous distonic radical ions with aryl radical sites. Chem Rev 2013; 113:6949-85. [PMID: 23987564 PMCID: PMC3889672 DOI: 10.1021/cr400121w] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Peggy E. Williams
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47906
| | | | - Linan Yang
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47906
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27
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Jankiewicz BJ, Vinueza NR, Kirkpatrick LM, Gallardo VA, Li G, Nash JJ, Kenttämaa HI. Does the 2,6-didehydropyridinium cation exist? J PHYS ORG CHEM 2013; 26:707-714. [PMID: 34262240 DOI: 10.1002/poc.3120] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Reactive intermediates are key species involved in many chemical and biochemical processes. For example, carbon-centered aromatic σ,σ-biradicals formed in biological systems from naturally occurring enediyne antitumor antibiotics are responsible for the irreversible cleavage of double-stranded DNA caused by these prodrugs. However, because of their high reactivity, it is very difficult or impossible to isolate and investigate these biradicals. The aromatic σ,σ-biradical, 2,6-didehydropyridine, has been speculated for many years to be formed in certain organic reactions; however, no definitive proof of its generation has been obtained. We report here the successful generation of protonated 2,6-didehydropyridine and the examination of its chemical properties in the gas phase by using a Fourier transform ion cyclotron resonance mass spectrometer. The results suggest that a mixture of singlet (ground) state and triplet (excited) state 2,6-didehydropyridinium cations was generated. The two different states show qualitatively different reactivity, with the triplet state showing greater Brønsted acidity than that of the singlet state. The triplet state also shows much greater radical reactivity than that of the singlet state, as expected because of the coupling of the nonbonding electrons in the singlet state.
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Affiliation(s)
- Bartłomiej J Jankiewicz
- B. J. Jankiewicz, N. R. Vinueza, L. M. Kirkpatrick, V. A. Gallardo, G. Li, J. J. Nash, H. I. Kenttämaa Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907-2084, USA.,B. J. Jankiewicz Current Address: Institute of Optoelectronics, Military University of Technology, Kaliskiego 2, 00-908 Warsaw, Poland
| | - Nelson R Vinueza
- B. J. Jankiewicz, N. R. Vinueza, L. M. Kirkpatrick, V. A. Gallardo, G. Li, J. J. Nash, H. I. Kenttämaa Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907-2084, USA
| | - Lindsey M Kirkpatrick
- B. J. Jankiewicz, N. R. Vinueza, L. M. Kirkpatrick, V. A. Gallardo, G. Li, J. J. Nash, H. I. Kenttämaa Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907-2084, USA
| | - Vanessa A Gallardo
- B. J. Jankiewicz, N. R. Vinueza, L. M. Kirkpatrick, V. A. Gallardo, G. Li, J. J. Nash, H. I. Kenttämaa Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907-2084, USA
| | - Guannan Li
- B. J. Jankiewicz, N. R. Vinueza, L. M. Kirkpatrick, V. A. Gallardo, G. Li, J. J. Nash, H. I. Kenttämaa Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907-2084, USA
| | - John J Nash
- B. J. Jankiewicz, N. R. Vinueza, L. M. Kirkpatrick, V. A. Gallardo, G. Li, J. J. Nash, H. I. Kenttämaa Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907-2084, USA
| | - Hilkka I Kenttämaa
- B. J. Jankiewicz, N. R. Vinueza, L. M. Kirkpatrick, V. A. Gallardo, G. Li, J. J. Nash, H. I. Kenttämaa Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907-2084, USA
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28
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Zhao Q, Zhu J, Huang ZA, Cao XY, Xia H. Conversions of Osmabenzyne and Isoosmabenzene. Chemistry 2012; 18:11597-603. [DOI: 10.1002/chem.201201558] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Indexed: 11/06/2022]
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29
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Cantillo D, Sheibani H, Kappe CO. Flash flow pyrolysis: mimicking flash vacuum pyrolysis in a high-temperature/high-pressure liquid-phase microreactor environment. J Org Chem 2012; 77:2463-73. [PMID: 22321044 DOI: 10.1021/jo3001645] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Flash vacuum pyrolysis (FVP) is a gas-phase continuous-flow technique where a substrate is sublimed through a hot quartz tube under high vacuum at temperatures of 400-1100 °C. Thermal activation occurs mainly by molecule-wall collisions with contact times in the region of milliseconds. As a preparative method, FVP is used mainly to induce intramolecular high-temperature transformations leading to products that cannot easily be obtained by other methods. It is demonstrated herein that liquid-phase high-temperature/high-pressure (high-T/p) microreactor conditions (160-350 °C, 90-180 bar) employing near- or supercritical fluids as reaction media can mimic the results obtained using preparative gas-phase FVP protocols. The high-T/p liquid-phase "flash flow pyrolysis" (FFP) technique was applied to the thermolysis of Meldrum's acid derivatives, pyrrole-2,3-diones, and pyrrole-2-carboxylic esters, producing the expected target heterocycles in high yields with residence times between 10 s and 10 min. The exact control over flow rate (and thus residence time) using the liquid-phase FFP method allows a tuning of reaction selectivities not easily achievable using FVP. Since the solution-phase FFP method does not require the substrate to be volatile any more--a major limitation in classical FVP--the transformations become readily scalable, allowing higher productivities and space-time yields compared with gas-phase protocols. Differential scanning calorimetry measurements and extensive DFT calculations provided essential information on pyrolysis energy barriers and the involved reaction mechanisms. A correlation between computed activation energies and experimental gas-phase FVP (molecule-wall collisions) and liquid-phase FFP (molecule-molecule collisions) pyrolysis temperatures was derived.
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Affiliation(s)
- David Cantillo
- Christian Doppler Laboratory for Microwave Chemistry and Institute of Chemistry, Karl-Franzens-University Graz, Heinrichstrasse 28, A-8010 Graz, Austria
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30
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Neuhaus P, Winkler M, Sander W. EPR spectroscopic and computational characterization of the 2-dehydro-m
-xylylene and 4-dehydro-m
-xylylene triradicals. J PHYS ORG CHEM 2011. [DOI: 10.1002/poc.1911] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Patrik Neuhaus
- Lehrstuhl für Organische Chemie II; Ruhr-Universität Bochum; Universitätsstr. 150 44780 Bochum Germany
| | - Michael Winkler
- Lehrstuhl für Organische Chemie II; Ruhr-Universität Bochum; Universitätsstr. 150 44780 Bochum Germany
| | - Wolfram Sander
- Lehrstuhl für Organische Chemie II; Ruhr-Universität Bochum; Universitätsstr. 150 44780 Bochum Germany
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31
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Li X, Paldus J. Force field of para- and metabenzyne diradicals: A multireference coupled-cluster study. J Chem Phys 2010; 132:114103. [DOI: 10.1063/1.3354947] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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32
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Winkler M, Sander W. Matrix Isolation and Electronic Structure of Di- and Tridehydrobenzenes. Aust J Chem 2010. [DOI: 10.1071/ch10113] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Within the past four decades, matrix isolation spectroscopy has emerged as the method of choice for obtaining direct structural information on benzynes and related dehydroaromatics. In combination with quantum chemical computations, detailed insight into the structure and reactivity of di-, tri-, and tetradehydrobenzenes has been obtained. This Review focuses on rather recent developments in aryne chemistry with a special emphasis on the matrix isolation of tridehydrobenzenes and related systems.
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33
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Abstract
The thermochemical properties of the benzynes have been the subject of investigation for nearly 50 years. This work provides an overview and assessment of all the experimental thermochemical properties that have been reported for the benzynes, or can be derived from reported thermochemical data. These properties include enthalpies of formation and thermochemical values that correspond to formation and dissociation of the benzynes by neutral and ionic processes. Thermochemical values are provided for both the ground-state singlet and the excited-state triplet states of the benzynes. The starting point for all the thermochemical consideration of the benzynes are the enthalpies of formation, which, in this work, are recommend to be 107.3 ± 3.5, 121.9 ± 3.1, and 138.0 ± 1.0 kcal mol–1 for ortho-, meta-, and para-benzyne, respectively (1 kcal mol–1 = 4.184 kJ mol–1). Whereas the paper predominantly focuses on the experimentally determined values, it also provides a comparison with theoretical studies that have examined the absolute thermochemical properties of the benzynes.
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34
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Abstract
Benzdiynes, which are more unsaturated than benzyne, were proposed as reactive intermediates in the pyrolyses of aromatic dianhydrides in 1966. The generation and direct observation of these highly unsaturated species has been an experimental challenge. More than 30 years later, the first direct observation of a benzdiyne, 1,4-bis(trifluoromethyl)-2,3,5,6-tetradehydrobenzene, was reported. We outline the progress in the generation and observation of benzdiynes as well as theoretical studies on the background of benzyne chemistry. Spectroscopic observation of the benzdiynes, in particular detection of an IR band due to the asymmetric stretching of the two triple bonds, in conjunction with quantum chemical computations reveals their multireference character. In connection with the studies for generating benzdiynes, the studies for generating bisarynes with extended π-systems and the most highly unsaturated cyclic C6 are briefly reviewed.
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35
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Wei H, Hrovat DA, Mo Y, Hoffmann R, Borden WT. The Contributions of Through-Bond Interactions to the Singlet−Triplet Energy Difference in 1,3-Dehydrobenzene. J Phys Chem A 2009; 113:10351-8. [DOI: 10.1021/jp905222f] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Haiyan Wei
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling, University of North Texas, 1155 Union Circle, #305070, Denton, Texas 76203-5070, Department of Chemistry, Western Michigan University, Kalamazoo, Michigan 49008, and Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853-1301
| | - David A. Hrovat
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling, University of North Texas, 1155 Union Circle, #305070, Denton, Texas 76203-5070, Department of Chemistry, Western Michigan University, Kalamazoo, Michigan 49008, and Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853-1301
| | - Yirong Mo
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling, University of North Texas, 1155 Union Circle, #305070, Denton, Texas 76203-5070, Department of Chemistry, Western Michigan University, Kalamazoo, Michigan 49008, and Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853-1301
| | - Roald Hoffmann
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling, University of North Texas, 1155 Union Circle, #305070, Denton, Texas 76203-5070, Department of Chemistry, Western Michigan University, Kalamazoo, Michigan 49008, and Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853-1301
| | - Weston Thatcher Borden
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling, University of North Texas, 1155 Union Circle, #305070, Denton, Texas 76203-5070, Department of Chemistry, Western Michigan University, Kalamazoo, Michigan 49008, and Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853-1301
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36
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Evangelista FA, Simmonett AC, Schaefer HF, Mukherjee D, Allen WD. A companion perturbation theory for state-specific multireference coupled cluster methods. Phys Chem Chem Phys 2009; 11:4728-41. [PMID: 19492126 DOI: 10.1039/b822910d] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A partitioning scheme is applied to the state-specific Mukherjee multireference coupled cluster method to derive a companion perturbation theory (Mk-MRPT2). A production-level implementation of Mk-MRPT2 is reported. The effectiveness of the Mk-MRPT2 method is demonstrated by application to the classic F(2) dissociation problem and the lowest-lying electronic states of meta-benzyne, including computations with up to 766 atomic orbitals. We show that Mk-MRPT2 theory is particularly useful in multireference focal point extrapolations to determine ab initio limits.
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Affiliation(s)
- Francesco A Evangelista
- Center for Computational Chemistry and Department of Chemistry, University of Georgia, Athens, GA 30602, USA
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37
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Crawford LA, McNab H, Mount AR, Wharton SI. Thermal Ring Contraction of Dibenz[b,f]azepin-5-yl Radicals: New Routes to Pyrrolo[3,2,1-jk]carbazoles. J Org Chem 2008; 73:6642-6. [PMID: 18693770 DOI: 10.1021/jo800637u] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Lynne A. Crawford
- School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K
| | - Hamish McNab
- School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K
| | - Andrew R. Mount
- School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K
| | - Stuart I. Wharton
- School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K
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38
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Venkataramani S, Winkler M, Sander W. Trifluoro-1,3,5-tridehydrobenzene. Angew Chem Int Ed Engl 2007; 46:4888-93. [PMID: 17568464 DOI: 10.1002/anie.200700536] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Sugumar Venkataramani
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
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39
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40
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Koziol L, Winkler M, Houk KN, Venkataramani S, Sander W, Krylov AI. The 1,2,3-Tridehydrobenzene Triradical: 2B or Not 2B? The Answer is 2A! J Phys Chem A 2007; 111:5071-80. [PMID: 17518455 DOI: 10.1021/jp0714522] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The molecular and electronic structure of 1,2,3-tridehydrobenzene was investigated by a variety of computational methods. The two lowest electronic states of the triradical are the (2)B(2) and (2)A(1) doublet states characterized by different interactions of the unpaired electrons. Vertically, the two states are well separated in energy-by 4.9 and 1.4 eV, respectively. However, due to different bonding patterns, their equilibrium structures are very different and, adiabatically, the two states are nearly degenerate. The adiabatic energy gap between the (2)B(2) and (2)A(1) states is estimated to be 0.7-2.1 kcal/mol, in favor of the (2)A(1) state. Harmonic vibrational frequencies and anharmonic corrections were calculated for both states. Comparison with the three experimentally observed IR transitions supports the assignment of the (2)A(1) ground state for the triradical with a weakly bonding distance of 1.67-1.69 A between the meta radical centers.
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Affiliation(s)
- Lucas Koziol
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, USA
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41
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Sander W, Winkler M, Cakir B, Grote D, Bettinger HF. Dehydrophenylnitrenes: Matrix Isolation and Photochemical Rearrangements. J Org Chem 2007; 72:715-24. [PMID: 17253786 DOI: 10.1021/jo061624b] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The photochemistry of 3-iodo-2,4,5,6-tetrafluorophenyl azide 8 and 3,5-diiodo-2,4,6-trifluorophenyl azide 9 was studied by IR and EPR spectroscopy in cryogenic argon and neon matrices. Both compounds form the corresponding nitrenes as primary photoproducts in photostationary equilibria with their azirine and ketenimine isomers. In contrast to fluorinated phenylnitrenes, ring-opened products are obtained upon short-wavelength irradiation of the iodine-containing systems, indicative of C-I bond cleavage in the nitrenes or didehydroazepines under these conditions. Neither 3-dehydrophenylnitrene 6 nor 3,5-didehydrophenylnitrene 7 could be detected directly. The structures of the acyclic photoproducts were identified by extensive comparison with DFT calculated spectra. Mechanistic aspects of the rearrangements leading to the observed products and the electronic properties of the title intermediates are discussed on the basis of DFT as well as high-level ab initio calculations. The computations indicate strong through-bond coupling of the exocyclic orbital in the meta position with the singly occupied in-plane nitrene orbital in the monoradical nitrenes. In contrast to the ortho or para isomers, this interaction results in low-spin ground states for meta nitrene radicals and a weakening of the C1-C2 bond causing the kinetic instability of these species even under low-temperature conditions. 3,5-Didehydrophenylnitrenes, on the other hand, in which a strong C3-C5 interaction reduces coupling of the radical sites with the nitrene unit, might be accessible synthetic targets if the intermediate formation of labile monoradicals could be circumvented.
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Affiliation(s)
- Wolfram Sander
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany.
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Affiliation(s)
- Paul G Wenthold
- Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA.
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Smith CE, Crawford TD, Cremer D. The structures of m-benzyne and tetrafluoro-m-benzyne. J Chem Phys 2005; 122:174309. [PMID: 15910034 DOI: 10.1063/1.1888570] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The structures of m-benzyne and its fluorinated derivative, tetrafluoro-m-benzyne, were investigated using coupled cluster methods including triple excitations [CCSD(T) and CCSDT], different reference wave functions (spin-restricted Hartree-Fock, spin-unrestricted Hartree-Fock, and Brueckner), and different basis sets [6-31G(d,p) and correlation-consistent valence triple-zeta (cc-pVTZ)]. The inclusion of triple excitations in conjunction with d- and f-type polarization functions is paramount to correctly describe through-bond delocalization of the monocyclic form. At the highest level of theory, the C1-C3 distance of the minimum energy form of m-benzyne is 2.0 A and the profile of the potential energy surface along the C1-C3 distance is that of an asymmetric, single well, in agreement with previous density-functional theory and coupled cluster studies. In addition, the calculated CCSD(T) fundamental frequencies are in excellent agreement with the measured infrared frequencies, thus confirming the monocyclic form of m-benzyne. For tetrafluoro-m-benzyne, however, the increased eclipsing strain between the ring-external C-X bonds stabilizes the bicyclo[3.1.0]hexatriene form: the C1-C3 distance is calculated at the CCSD(T)/cc-pVTZ level to be approximately 1.75 A, which is in the range of elongated CC bonds. Computed harmonic vibrational frequencies compare reasonably well with the experimental neon-matrix difference spectrum and provide further evidence for the existence of a bicyclic form.
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Cremeens ME, Hughes TS, Carpenter BK. Mechanistic Studies on the Cyclization of (Z)-1,2,4-Heptatrien-6-yne in Methanol: A Possible Nonadiabatic Thermal Reaction. J Am Chem Soc 2005; 127:6652-61. [PMID: 15869286 DOI: 10.1021/ja0445443] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Myers et al. pyrolyzed (Z)-1,2,4-heptatrien-6-yne (1) in methanol at 100 degrees C and observed benzylmethyl ether (2) as a major product and 2-phenylethanol (3) as a minor product. If a biradical intermediate, such as the open-shell singlet state of alpha,3-didehydrotoluene (4), was the only intermediate generated by the cyclization, then reaction with methanol might be expected to afford 2-phenylethanol as the principal product. The question that has been of interest since its first discovery is the origin of the principal product of the title reaction, benzylmethyl ether. This report considers three mechanisms for formation of the benzylmethyl ether: direct methanol participation in the cyclization of the reactant, partial ether formation from the biradical 4, or involvement of the closed-shell zwitterionic state of alpha,3-didehydrotoluene (5). A fourth mechanism, involving a cyclic allene intermediate, has been ruled out by earlier studies. In the present work, the first two mechanisms are ruled out by experiment and/or calculation. The remaining one, involving the zwitterion, is shown to be consistent with experimental and computational data only if a component of the reaction follows a nonadiabatic course.
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Affiliation(s)
- Matthew E Cremeens
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301, USA
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Nash JJ, Nizzi KE, Adeuya A, Yurkovich MJ, Cramer CJ, Kenttämaa HI. Demonstration of Tunable Reactivity for meta-Benzynes. J Am Chem Soc 2005; 127:5760-1. [PMID: 15839653 DOI: 10.1021/ja0449473] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A combined computational and experimental study on the gas-phase structures and reactivities of charged 1,3-didehydroarenes (meta-benzynes) demonstrates that the reactivity of such biradicals can be "tuned" by using appropriate substituents. Substituents that destabilize a specific zwitterionic resonance structure can change the reactivity of the biradical from mildly carbocationic to radical-like. These substituent effects are not the result of changes in the singlet-triplet gaps of the biradicals, but rather reflect changes in the potential energy surfaces for the dehydrocarbon separation.
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Affiliation(s)
- John J Nash
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
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Winkler M. The Fulvenediyls and Related Biradicals: Molecular and Electronic Structure. J Phys Chem A 2005; 109:1240-6. [PMID: 16833435 DOI: 10.1021/jp0461044] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structures, stabilities, and electronic properties of the nine fulvenediyls have been investigated and compared to the isomeric benzynes using density functional theory (DFT) and ab initio multireference configuration interaction methods (MRCI). Given the significant biradical character of several singlet fulvenediyls, the BLYP method reproduces the relative energies of these systems rather accurately. In contrast, some triplet states (3A'-12, 3A'-13, and 3B2-14) suffer from artifactual symmetry breaking towards a nonplanar geometry at the DFT level. The structures and properties of the title biradicals are readily rationalized within the framework of through-space and through-bond molecular orbital interactions. The degree of coupling between the formally unpaired electrons strongly depends on the number and arrangement of intervening sigma-bonds, and often parallels the trends observed for annellated arynes of similar topology. In some cases, novel structural patterns can be identified that are characteristic of five-membered-ring systems. These similarities and differences between five- and six-membered-ring arynes are discussed on the basis of molecular orbital arguments.
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Affiliation(s)
- Michael Winkler
- Lehrstuhl für Organische Chemie II der Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
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