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Euringer L, Holzapfel M, Krummenacher I, Franz M, Richert S, Braunschweig H, Lambert C. Tuning Electron Transfer Coupling and Exchange Interaction in Bis-triarylamine Radical Cations and Dications by Bridge Electron Density. J Am Chem Soc 2024; 146:27679-27689. [PMID: 39316417 DOI: 10.1021/jacs.4c09221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/25/2024]
Abstract
The influence of the electron density of a bridge connecting two redox centers on both the intervalence hole transfer and the magnetic superexchange was investigated in a series of bridged bis-triarylamine mono- and dications. In this series, the bridge was 2,7-fluorenyl, where the bridge electron density was modified by substituents at the 9-position. For the mixed-valence monocations, the observation of both an intervalence charge transfer (IVCT) band and an absorption band associated with an electron transfer from the bridging fluorene to the triarylamine radical cation centers allowed determination of the electron transfer couplings in the framework of the three-state generalized Mulliken-Hush theory. Comparison of the derived couplings with those obtained from a classical two-state approach demonstrates an enhancement of the electronic coupling which increases with decreasing bridge state energy. For the dicationic diradical counterparts, the singlet-triplet gap (exchange interaction) was determined both experimentally and by quantum chemical methods. Hereby, an increase of antiferromagnetic coupling with a lowering of the bridge state energy by electron donating substituents was observed. Analysis of the involved molecular orbitals suggests that the ferromagnetic coupling is inversely proportional to the square of the bridge energy, which is also supported by the experimental findings. This influence of the bridge state energy on both types of interactions, electron transfer and magnetic exchange, provides a design guideline for fine-tuning the properties of electronically coupled organic redox dyads by variation of the bridge electron density.
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Affiliation(s)
- Leon Euringer
- Institut für Organische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Marco Holzapfel
- Institut für Organische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Ivo Krummenacher
- Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Michael Franz
- Institute of Physical Chemistry, University of Freiburg, Albertstraße 21, 79104 Freiburg, Germany
| | - Sabine Richert
- Institute of Physical Chemistry, University of Freiburg, Albertstraße 21, 79104 Freiburg, Germany
| | - Holger Braunschweig
- Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Christoph Lambert
- Institut für Organische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Center für Nanosystems Chemistry, Universität Würzburg, Theodor-Boveri-Weg, 97074 Würzburg, Germany
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2
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Sugiura S, Kubo T, Haketa Y, Hori Y, Shigeta Y, Sakai H, Hasobe T, Maeda H. Deprotonation-Induced and Ion-Pairing-Modulated Diradical Properties of Partially Conjugated Pyrrole-Quinone Conjunction. J Am Chem Soc 2023; 145:8122-8129. [PMID: 36976916 DOI: 10.1021/jacs.3c01025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
Quinoidal molecules based on dipyrrolyldiketone boron complexes (QPBs), in which pyrrole units were connected by a partially conjugated system as a singlet spin coupler, were synthesized. QPB, which was stabilized by the introduction of a benzo unit at the pyrrole β-positions, formed a closed-shell tautomer conformation that showed near-infrared absorption. The deprotonated species, monoanion QPB- and dianion QPB2-, showing over 1000 nm absorption, were formed by the addition of bases, providing ion pairs in combination with countercations. Diradical properties were observed in QPB2-, whose hyperfine coupling constants were modulated by ion-pairing with π-electronic and aliphatic cations, demonstrating cation-dependent diradical properties. VT NMR and ESR along with a theoretical study revealed that the singlet diradical was more stable than the triplet diradical.
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Affiliation(s)
- Shinya Sugiura
- Department of Applied Chemistry, College of Life Sciences, Ritsumeikan University, Kusatsu 525-8577, Japan
| | - Takashi Kubo
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan
| | - Yohei Haketa
- Department of Applied Chemistry, College of Life Sciences, Ritsumeikan University, Kusatsu 525-8577, Japan
| | - Yuta Hori
- Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8577, Japan
| | - Yasuteru Shigeta
- Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8577, Japan
| | - Hayato Sakai
- Department of Chemistry, Faculty of Science and Technology, Keio University, Yokohama 223-8522, Japan
| | - Taku Hasobe
- Department of Chemistry, Faculty of Science and Technology, Keio University, Yokohama 223-8522, Japan
| | - Hiromitsu Maeda
- Department of Applied Chemistry, College of Life Sciences, Ritsumeikan University, Kusatsu 525-8577, Japan
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3
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Hewitt P, Shultz DA, Kirk ML. Magnetic Exchange Coupling through the Nonalternant Cyclopentadienyl π-System of Ferrocene. Org Lett 2021; 23:8235-8239. [PMID: 34586811 DOI: 10.1021/acs.orglett.1c02982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electronic and magnetic coupling through nonalternant π-systems is an area of intense interest in photonics and molecular electronics research, yet relatively little is known regarding coupling through nonalternant π-systems. Herein we present magnetic exchange coupling in two semiquinone-based biradicals: 1,3-SQ2Fc has two semiquinone radicals attached to the one- and three-positions of the same cyclopentadienyl ligand (a nonalternant π-system) of ferrocene, whereas 1,1'-SQ2Fc has one semiquinone radical attached to each of the two cyclopentadienyl ligands of ferrocene.
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Affiliation(s)
- Patrick Hewitt
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - David A Shultz
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Martin L Kirk
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
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Hewitt P, Shultz DA, Kirk ML. Rules for Magnetic Exchange in Azulene-Bridged Biradicals: Quo Vadis? J Org Chem 2021; 86:15577-15587. [PMID: 34644082 DOI: 10.1021/acs.joc.1c02085] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Electronic coupling through organic bridges facilitates magnetic exchange interactions and controls electron transfer and single-molecule device electron transport. Electronic coupling through alternant π-systems (e.g., benzene) is better understood than the corresponding coupling through nonalternant π-systems (e.g., azulene). Herein, we examine the structure, spectroscopy, and magnetic exchange coupling in two biradicals (1,3-SQ2Az and 1,3-SQ-Az-NN; SQ = the zinc(II) complex of spin-1/2 semiquinone radical anion, NN = spin-1/2 nitronylnitroxide; Az = azulene) that possess nonalternant azulene π-system bridges. The SQ radical spin density in both molecules is delocalized into the Az π-system, while the NN spin is effectively localized onto the five-atom ONCNO π-system of NN radical. The spin distributions and interactions are probed by EPR spectroscopy and magnetic susceptibility measurements. We find that J = +38 cm-1 for 1,3-SQ2Az and J = +9 cm-1 for 1,3-SQ-Az-NN (H=-2JS^SQ·S^SQorNN). Our results highlight the differences in exchange coupling mediated by azulene compared to exchange coupling mediated by alternant π-systems.
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Affiliation(s)
- Patrick Hewitt
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - David A Shultz
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Martin L Kirk
- Department of Chemistry, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
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5
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Poddel'sky AI, Smolyaninov IV, Druzhkov NO, Fukin GK. Heterometallic antimony(V)-zinc and antimony(V)-copper complexes comprising catecholate and diazadiene as redox active centers. J Organomet Chem 2021. [DOI: 10.1016/j.jorganchem.2021.121994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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6
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Cui H, Hu ZB, Chen C, Ruan H, Fang Y, Zhang L, Zhao Y, Tan G, Song Y, Wang X. A high-spin diradical dianion and its bridged chemically switchable single-molecule magnet. Chem Sci 2021; 12:9998-10004. [PMID: 34377394 PMCID: PMC8317668 DOI: 10.1039/d1sc01932e] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 06/21/2021] [Indexed: 11/21/2022] Open
Abstract
Triplet diradicals have attracted tremendous attention due to their promising application in organic spintronics, organic magnets and spin filters. However, very few examples of triplet diradicals with singlet–triplet energy gaps (ΔEST) over 0.59 kcal mol−1 (298 K) have been reported to date. In this work, we first proved that the dianion of 2,7-di-tert-butyl-pyrene-4,5,9,10-tetraone (2,7-tBu2-PTO) was a triplet ground state diradical in the magnesium complex 1 with a singlet–triplet energy gap ΔEST = 0.94 kcal mol−1 (473 K). This is a rare example of stable diradicals with singlet–triplet energy gaps exceeding the thermal energy at room temperature (298 K). Moreover, the iron analog 2 containing the 2,7-tBu2-PTO diradical dianion was isolated, which was the first single-molecule magnet bridged by a diradical dianion. When 2 was doubly reduced to the dianion salt 2K2, single-molecule magnetism was switched off, highlighting the importance of diradicals in single-molecule magnetism. We report a triplet diradical dianion in magnesium complex with ΔEST = 0.94 kcal mol−1 (473 K). Its iron analog is the first single-molecule magnet bridged by a diradical dianion, and the SMM property is switched off through two-electron reduction.![]()
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Affiliation(s)
- Haiyan Cui
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University Nanjing 210023 China .,Jiangsu Key Laboratory of Pesticide Science, College of Sciences, Nanjing Agricultural University Nanjing 210095 China
| | - Zhao-Bo Hu
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University Nanjing 210023 China
| | - Chao Chen
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University Nanjing 210023 China
| | - Huapeng Ruan
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University Nanjing 210023 China
| | - Yong Fang
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University Nanjing 210023 China
| | - Li Zhang
- Center of Materials Science and Engineering, Guangxi University of Science and Technology Liuzhou 545006 China
| | - Yue Zhao
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University Nanjing 210023 China
| | - Gengwen Tan
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University Suzhou 215123 China
| | - You Song
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University Nanjing 210023 China
| | - Xinping Wang
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University Nanjing 210023 China
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7
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Chattopadhyay S. The effect of substituents on energy splitting in organic radicals: Quantitative cognizance from ab initio studies. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2018.08.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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8
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Mondal D, Majee MC, Kundu S, Mörtel M, Abbas G, Endo A, Khusniyarov MM, Chaudhury M. Dinuclear Iron(III) and Cobalt(III) Complexes Featuring a Biradical Bridge: Their Molecular Structures and Magnetic, Spectroscopic, and Redox Properties. Inorg Chem 2018; 57:1004-1016. [DOI: 10.1021/acs.inorgchem.7b02340] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dhrubajyoti Mondal
- Department of Inorganic
Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
| | - Mithun Chandra Majee
- Department of Inorganic
Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
| | - Sanchita Kundu
- Department of Inorganic
Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
| | - Max Mörtel
- Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Egerlandstrasse
1, 91058 Erlangen, Germany
| | - Ghulam Abbas
- Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Egerlandstrasse
1, 91058 Erlangen, Germany
| | - Akira Endo
- Department
of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1
Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan
| | - Marat M. Khusniyarov
- Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Egerlandstrasse
1, 91058 Erlangen, Germany
| | - Muktimoy Chaudhury
- Department of Inorganic
Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
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9
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A comparative study on seniority-based MO and VB calculations of the singlet and triplet energy gaps of open-shell molecules. COMPUT THEOR CHEM 2017. [DOI: 10.1016/j.comptc.2017.03.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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10
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Lloveras V, Badetti E, Wurst K, Chechik V, Veciana J, Vidal-Gancedo J. Magnetic and Electrochemical Properties of a TEMPO-Substituted Disulfide Diradical in Solution, in the Crystal, and on a Surface. Chemistry 2016; 22:1805-15. [PMID: 26743879 DOI: 10.1002/chem.201503306] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 11/09/2015] [Indexed: 12/15/2022]
Abstract
A study of the magnetic and electrochemical properties of a TEMPO-substituted disulfide diradical in three different environments was carried out: in solution, in the crystal, and as a self-assembled monolayer (SAM) on an Au(111) substrate, and the relationship between them was explored. In solution, this flexible diradical shows a strong spin-exchange interaction between the two nitroxide functions that depends on the temperature and solvent. Structural, dynamic, and thermodynamic information has been extracted from the EPR spectra of this dinitroxide. The magnetic interactions in the crystal include intra- and intermolecular contributions, which have been studied separately and shown to be antiferromagnetic in both cases. Finally, we demonstrate that both the magnetic and electrochemical properties are preserved upon chemisorption of the diradical on a gold surface. The resulting SAM displayed anisotropic magnetic properties, and angle-resolved EPR spectra of the monocrystal allowed a rough determination of the orientation of the molecules in the SAM.
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Affiliation(s)
- Vega Lloveras
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB s/n, 08193, Cerdanyola del Vallès, Spain.,CIBER de Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN), Barcelona, Spain), Fax
| | - Elena Badetti
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB s/n, 08193, Cerdanyola del Vallès, Spain.,CIBER de Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN), Barcelona, Spain), Fax
| | - Klaus Wurst
- Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Center for Chemistry and Biomedicine, Innrain 80-82, 6020, Innsbruck, Austria
| | - Victor Chechik
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
| | - Jaume Veciana
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB s/n, 08193, Cerdanyola del Vallès, Spain.,CIBER de Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN), Barcelona, Spain), Fax
| | - José Vidal-Gancedo
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB s/n, 08193, Cerdanyola del Vallès, Spain. .,CIBER de Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN), Barcelona, Spain), Fax.
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11
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Loughrey JJ, Patmore NJ, Baldansuren A, Fielding AJ, McInnes EJL, Hardie MJ, Sproules S, Halcrow MA. Platinum(ii) complexes of mixed-valent radicals derived from cyclotricatechylene, a macrocyclic tris-dioxolene. Chem Sci 2015; 6:6935-6948. [PMID: 29861932 PMCID: PMC5951140 DOI: 10.1039/c5sc02776d] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 08/18/2015] [Indexed: 01/10/2023] Open
Abstract
Three complexes of cyclotricatechylene (H6ctc), [{PtL}3(μ3-ctc)], have been synthesised: (L = 1,2-bis(diphenylphosphino)benzene {dppb}, 1; L = 1,2-bis(diphenylphosphino)ethane {dppe}, 2; L = 4,4'-bis(tert-butyl)-2,2'-bipyridyl { t Bu2bipy}, 3). The complexes show three low-potential, chemically reversible voltammetric oxidations separated by ca. 180 mV, corresponding to stepwise oxidation of the [ctc]6- catecholato rings to the semiquinonate level. The redox series [1]0/1+/2+/3+ and [3]0/1+/2+/3+ have been characterised by UV/vis/NIR spectroelectrochemistry. The mono- and di-cations have class II mixed valent character, with reduced radical delocalisation compared to an analogous bis-dioxolene system. The SOMO composition of [1˙]+ and [3˙]+ has been delineated by cw EPR, ENDOR and HYSCORE spectroscopies, with the aid of two monometallic model compounds [PtL(DBsq˙)]+ (DBsqH = 3,5-bis(tert-butyl)-1,2-benzosemiquinone; L = dppe or t Bu2bipy). DF and time-dependent DF calculations confirm these interpretations, and demonstrate changes to spin-delocalisation in the ctc macrocycle as it is sequentially oxidised.
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Affiliation(s)
- Jonathan J Loughrey
- School of Chemistry , University of Leeds , Woodhouse Lane , Leeds LS2 9JT , UK .
| | - Nathan J Patmore
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK
| | - Amgalanbaatar Baldansuren
- School of Chemistry and Photon Science Institute , University of Manchester , Oxford Road , Manchester M13 9PL , UK
| | - Alistair J Fielding
- School of Chemistry and Photon Science Institute , University of Manchester , Oxford Road , Manchester M13 9PL , UK
| | - Eric J L McInnes
- School of Chemistry and Photon Science Institute , University of Manchester , Oxford Road , Manchester M13 9PL , UK
| | - Michaele J Hardie
- School of Chemistry , University of Leeds , Woodhouse Lane , Leeds LS2 9JT , UK .
| | - Stephen Sproules
- WestCHEM , School of Chemistry , University of Glasgow , Glasgow G12 8QQ , UK .
| | - Malcolm A Halcrow
- School of Chemistry , University of Leeds , Woodhouse Lane , Leeds LS2 9JT , UK .
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13
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Piskunov AV, Ershova IV, Bogomyakov AS, Starikov AG, Fukin GK, Cherkasov VK. Indirect Magnetic Exchange between o-Iminosemiquinonate Ligands Controlled by Apical Substituent in Pentacoordinated Gallium(III) Complexes. Inorg Chem 2015; 54:6090-9. [DOI: 10.1021/acs.inorgchem.5b00520] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alexander V. Piskunov
- G. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, Tropinina str. 49, Nizhny
Novgorod 603950, Russian Federation
- Nizhny Novgorod State University, Gagarina ave. 23, Nizhny
Novgorod 603950, Russian Federation
| | - Irina V. Ershova
- G. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, Tropinina str. 49, Nizhny
Novgorod 603950, Russian Federation
| | - Artem S. Bogomyakov
- International Tomography Center, Siberian Branch of the Russian Academy of Sciences, 3a Institutskaya str., 630090 Novosibirsk, Russian Federation
| | - Andrey G. Starikov
- Southern Scientific Center of Russian Academy of Sciences, 41 Chehova Ave., 344006 Rostov on Don, Russian Federation
| | - Georgy K. Fukin
- G. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, Tropinina str. 49, Nizhny
Novgorod 603950, Russian Federation
- Nizhny Novgorod State University, Gagarina ave. 23, Nizhny
Novgorod 603950, Russian Federation
| | - Vladimir K. Cherkasov
- G. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, Tropinina str. 49, Nizhny
Novgorod 603950, Russian Federation
- Nizhny Novgorod State University, Gagarina ave. 23, Nizhny
Novgorod 603950, Russian Federation
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14
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Loughrey JJ, Sproules S, McInnes EJL, Hardie MJ, Halcrow MA. Stable mixed-valent radicals from platinum(II) complexes of a bis(dioxolene) ligand. Chemistry 2014; 20:6272-6. [PMID: 24488824 PMCID: PMC4164269 DOI: 10.1002/chem.201304848] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Indexed: 11/13/2022]
Abstract
Three diplatinum(II) complexes [{PtL}2(μ-thea)] (H4thea=2,3,6,7-tetrahydroxy-9,10-dimethyl-9,10-dihydro-9,10-ethanoanthracene) have been prepared, with diphosphine or bipyridyl “L” co-ligands. One-electron oxidation of these complexes gave radical cations containing a mixed-valent [thea]3− ligand with discrete catecholate and semiquinonate centers separated by quaternary methylene spacers. The electronic character of these radicals is near the Robin–Day class II/III border determined by UV/Vis/NIR and EPR spectroscopies. Crystal-structure determinations and a DFT calculation imply that oxidation of the thea4− ligand may lead to an increased through-space interaction between the dioxolene π systems.
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Affiliation(s)
- Jonathan J Loughrey
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT (UK), Fax: (+44) 113-343-6565; Current address: Department of Chemistry and Biochemistry, University of Arizona, P.O. Box 210041, 1306 East University Blvd., Tucson, AZ 85721-0041 (USA)
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15
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Manipulating the singlet–triplet energy gaps of arene-fused bis(1,2,3-dithiazoles): A computational study. Polyhedron 2013. [DOI: 10.1016/j.poly.2013.03.054] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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17
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Porel M, Ottaviani MF, Jockusch S, Turro NJ, Ramamurthy V. Control of spin–spin exchange interactions in polynitroxides through inclusion within γ-cyclodextrin. RSC Adv 2013. [DOI: 10.1039/c2ra22285j] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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18
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Poddel’sky AI, Smolyaninov IV, Vavilina NN, Kurskii YA, Berberova NT, Cherkasov VK, Abakumov GA. Triaryl- and trialkylantimony(V) Bis(catecholates) based on 1,1′-spirobis[3,3-dimethylindanequinone-5,6]: Spectroscopic and electrochemical studies. RUSS J COORD CHEM+ 2012. [DOI: 10.1134/s1070328412040094] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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19
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Sloop JC, Shultz DA, Marcus MB, Shepler B. Linear free-energy relationships in semiquinone species and their Mn(II) and Cu(II) complexes. J PHYS ORG CHEM 2012. [DOI: 10.1002/poc.1878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Joseph C. Sloop
- School of Science and Technology; Georgia Gwinnett College; 1000 University Center Lane; Lawrenceville; GA; 30043; USA
| | - David A. Shultz
- Department of Chemistry; North Carolina State University; Raleigh; NC; 27695; USA
| | | | - Benjamin Shepler
- School of Science and Technology; Georgia Gwinnett College; 1000 University Center Lane; Lawrenceville; GA; 30043; USA
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Kanzaki Y, Shiomi D, Sato K, Takui T. Biradical Paradox Revisited Quantitatively: A Theoretical Model for Self-Associated Biradical Molecules as Antiferromagnetically Exchange Coupled Spin Chains in Solution. J Phys Chem B 2012; 116:1053-9. [DOI: 10.1021/jp211391x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yuki Kanzaki
- Department of Chemistry, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Daisuke Shiomi
- Department of Chemistry, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Kazunobu Sato
- Department of Chemistry, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Takeji Takui
- Department of Chemistry, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
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Ottaviani MF, Modelli A, Zeika O, Jockusch S, Moscatelli A, Turro NJ. EPR Analysis and DFT Computations of a Series of Polynitroxides. J Phys Chem A 2011; 116:174-84. [DOI: 10.1021/jp211082t] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- M. Francesca Ottaviani
- Department of Earth, Life and Environment Sciences (DiSTeVA), University of Urbino, 61029 Urbino, Italy
| | - Alberto Modelli
- Department of Chemistry “G. Ciamician”, University of Bologna, 40126 Bologna, Italy, and Centro Interdipartimentale di Ricerca in Scienze Ambientali (CIRSA), 48123 Ravenna, Italy
| | - Olaf Zeika
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Steffen Jockusch
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Alberto Moscatelli
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Nicholas J. Turro
- Department of Chemistry, Columbia University, New York, New York 10027, United States
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22
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Sloop JC, Shultz DA, Coote T, Shepler B, Sullivan U, Kampf JW, Boyle PD. Synthesis of and structure-property relationships in zinc complexes of bis-metaphenylene semiquinone biradical species. J PHYS ORG CHEM 2011. [DOI: 10.1002/poc.1917] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Joseph C. Sloop
- School of Science and Technology; Georgia Gwinnett College; 1000 University Center Lane Lawrenceville GA 30043 USA
| | - David A. Shultz
- Department of Chemistry; North Carolina State University; Raleigh NC 27695 USA
| | - Tashni Coote
- Department of Chemistry; North Carolina State University; Raleigh NC 27695 USA
| | - Benjamin Shepler
- School of Science and Technology; Georgia Gwinnett College; 1000 University Center Lane Lawrenceville GA 30043 USA
| | - Ubie Sullivan
- Department of Chemistry; North Carolina State University; Raleigh NC 27695 USA
| | - Jeff W. Kampf
- Department of Chemistry; University of Michigan; Ann Arbor MI 48109 USA
| | - Paul D. Boyle
- Department of Chemistry; North Carolina State University; Raleigh NC 27695 USA
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23
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Zaware SB, Gonnade RG, Srinivas D, Khan A, Rane SY. Antioxidant and anticancer activities of supramolecularly controlled magnetostructural halo-oximes of lawsone. NEW J CHEM 2011. [DOI: 10.1039/c1nj20176j] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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24
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Brook DJR, Yee GT, Hundley M, Rogow D, Wong J, Van-Tu K. Geometric Control of Ground State Multiplicity in a Copper(I) Bis(verdazyl) Complex. Inorg Chem 2010; 49:8573-7. [DOI: 10.1021/ic1011764] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- David J. R. Brook
- Department of Chemistry, San José State University, San José, California 95192
| | - Gordon T. Yee
- Department of Chemistry, Virginia Polytechnic University, Blacksburg, Virginia
| | - Mike Hundley
- Department of Chemistry, Virginia Polytechnic University, Blacksburg, Virginia
| | - David Rogow
- Department of Chemistry, University of California, Santa Cruz, California
| | - Janice Wong
- Department of Chemistry, San José State University, San José, California 95192
| | - Khanh Van-Tu
- Department of Chemistry, San José State University, San José, California 95192
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Poddel’sky AI, Smolyaninov IV, Kurskii YA, Berberova NT, Cherkasov VK, Abakumov GA. New dioxygen-inert triphenylantimony(v) catecholate complexes based on o-quinones with electron-withdrawing groups. Russ Chem Bull 2010. [DOI: 10.1007/s11172-009-0052-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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26
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Poddel’sky AI, Vavilina NN, Somov NV, Cherkasov VK, Abakumov GA. Triethylantimony(V) complexes with bidentate O,N-, O,O- and tridentate O,N,O′-coordinating o-iminoquinonato/o-quinonato ligands: Synthesis, structure and some properties. J Organomet Chem 2009. [DOI: 10.1016/j.jorganchem.2009.06.027] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Fehir RJ, McCusker JK. Differential Polarization of Spin and Charge Density in Substituted Phenoxy Radicals. J Phys Chem A 2009; 113:9249-60. [DOI: 10.1021/jp905314h] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Richard J. Fehir
- Contribution from the Department of Chemistry, Michigan State University, East Lansing, Michigan 48824
| | - James K. McCusker
- Contribution from the Department of Chemistry, Michigan State University, East Lansing, Michigan 48824
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Manohar PU, Koziol L, Krylov AI. Effect of a Heteroatom on Bonding Patterns and Triradical Stabilization Energies of 2,4,6-Tridehydropyridine versus 1,3,5-Tridehydrobenzene. J Phys Chem A 2009; 113:2591-9. [DOI: 10.1021/jp810522e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Prashant U. Manohar
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482
| | - Lucas Koziol
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482
| | - Anna I. Krylov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482
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29
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Rane S, Ahmed K, Salunke-Gawali S, Zaware SB, Srinivas D, Gonnade R, Bhadbhade M. Vitamin K3 family members – Part II: Single crystal X-ray structures, temperature-induced packing polymorphism, magneto-structural correlations and probable anti-oncogenic candidature. J Mol Struct 2008. [DOI: 10.1016/j.molstruc.2008.05.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Gilroy JB, McKinnon SDJ, Kennepohl P, Zsombor MS, Ferguson MJ, Thompson LK, Hicks RG. Probing Electronic Communication in Stable Benzene-Bridged Verdazyl Diradicals. J Org Chem 2007; 72:8062-9. [PMID: 17887707 DOI: 10.1021/jo7014449] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two benzene-bridged N,N'-bis(isopropyl)6-oxoverdazyl diradicals 7a (1,4-benzene-bridged) and 7b (1,3-benzene-bridged) were prepared and studied by an array of physicochemical techniques aimed at elucidating the intramolecular electronic and magnetic coupling between verdazyl chromophores. The very high stability of these diradicals permits comprehensive investigations of their properties for the first time. The UV-vis spectra suggest negligible direct conjugative overlap involving the radical SOMOs, although significant differences in higher energy absorptions suggest that radical orbitals other than the SOMO are likely communicating via the central p-phenylene bridge in 7a. The electrochemical features of the two diradicals are nearly identical; in each derivative, both radicals are oxidized essentially independently while the reductions occur in a stepwise manner with differences of approximately 100 mV between the two reductions. EPR and magnetic susceptibility collectively indicate that the para-bridged diradical is weakly antiferromagnetically coupled while the meta analogue is weakly ferromagnetically coupled, in accord with the topology of the substitution pattern on the central benzene ring.
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Affiliation(s)
- Joe B Gilroy
- Department of Chemistry, University of Victoria, P.O. Box 3065, Victoria, BC, Canada V8W 3V6
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32
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Breher F. Stretching bonds in main group element compounds—Borderlines between biradicals and closed-shell species. Coord Chem Rev 2007. [DOI: 10.1016/j.ccr.2006.09.007] [Citation(s) in RCA: 271] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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33
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Shultz DA, Sloop JC, Coote TA, Beikmohammadi M, Kampf J, Boyle PD. Substituent Effects on Exchange Coupling: 5-Aryl-Substituted Semiquinones and Their Complexes with MnII and CuII. Inorg Chem 2007; 46:273-7. [PMID: 17198436 DOI: 10.1021/ic061807g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of functionalized radical anion semiquinone (SQ-Ar) ligands and their MnII- and CuIIhydro-tris(3-cumenyl-5-methylpyrazolyl)borate (TpCum,MeMII) complexes were prepared and characterized. The semiquinone ligands have substituted phenyl rings (Ar = -C6H5NO2, -C6H5OMe, -C6H5-tert-Bu, etc.) attached to the SQ 5-position. Despite the "remoteness" of the phenyl ring substituents, the MII-SQ exchange parameters, J, were found to vary nearly 3-fold. Attempts to quantify the substituent effects on J are complicated by the fact that not all complexes could be structurally characterized. As such, substituent effects and phenyl-ring torsion angles could conspire to produce the observed variation in J values. Although there is no clear trend in the J values as a function of SQ substituent for the MnII complexes, for the CuII complexes, electron-withdrawing substituents on the phenyl ring have greater ferromagnetic J values than the CuII complexes of SQ ligands with electron-donating substituents. This trend suggests a FM contribution from MLCT excited states in the copper complexes.
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Affiliation(s)
- David A Shultz
- Department of Chemistry, North Carolina State University, P.O. Box 8204, Raleigh, North Carolina 27695, USA.
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Shultz DA, Sloop JC, Washington G. Design, Synthesis, and Properties of Conformationally Fixed Semiquinone Monoradical Species. J Org Chem 2006; 71:9104-13. [PMID: 17109536 DOI: 10.1021/jo061502j] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The design of novel, functionalized semiquinone (SQ) ligands which combine structural rigidity and electron-withdrawing, electron-donating, and electroneutral substituents enables investigation of multiple structure-property relationships and building blocks for new materials, including components of sensors, switches, and molecular spintronics. Along these lines, we report the synthesis of several new SQ ligands containing fused heterocyclic ring systems. Using both electron paramagnetic resonance spectroscopy and quantum chemical calculations, we show how spin density is affected by the fused ring system substituents.
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Affiliation(s)
- David A Shultz
- Department of Chemistry, North Carolina State University, P.O. Box 8204, Raleigh, North Carolina 27695, USA
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35
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Brook DJR, Yee GT. Radical−Radical Interaction through a Saturated Link: Methylenebis-6-oxoverdazyl. J Org Chem 2006; 71:4889-95. [PMID: 16776518 DOI: 10.1021/jo060165b] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The diradical methylenebis(1,5-diisopropyl-6-oxoverdazyl) was synthesized by benzoquinone oxidation of the corresponding bis(tetrazane). The diradical crystallizes in the monoclinic space group C2/c with cell parameters a = 21.1411(8) A, b = 12.4781(5) A, c = 8.2457(3) A, beta = 108.638(2) degrees, V = 2061.15 A3, Z = 4. Magnetic measurements indicate the diradical has a singlet ground state and triplet excited state at 150 cm(-1). Interaction between the nonconjugated radical centers is also seen in the UV-vis spectrum as a broad shoulder near 500 nm that is not apparent in the spectrum of the monoradical.
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Affiliation(s)
- David J R Brook
- Department of Chemistry, Santa Clara University, Santa Clara, California 95053, USA.
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Hayakawa K, Shiomi D, Ise T, Sato K, Takui T. Pyridine-substituted nitronyl nitroxide biradicals: a triplet (S = 1) ground state lasting out N-methylation. ACTA ACUST UNITED AC 2006. [DOI: 10.1039/b609760j] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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37
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Terada E, Okamoto T, Kozaki M, Masaki ME, Shiomi D, Sato K, Takui T, Okada K. Exchange Interaction of 5,5‘-(m- and p-Phenylene)bis(10-phenyl-5,10-dihydrophenazine) Dications and Related Analogues. J Org Chem 2005; 70:10073-81. [PMID: 16292842 DOI: 10.1021/jo051791w] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[structures: see text] 5,5'-(m-Phenylene)bis[(10-aryl-5,10-dihydrophenazine) dications, 3a2+ and 3b2+, and their p-analogues 4a2+ and 4b2+, were prepared, and their exchange interaction was investigated. The EPR spectra of these dications at 123 K in a butyronitrile matrix showed the population of a triplet state. The temperature dependence of the EPR signal intensity (absolute value(delta m(s)) = 2) showed that these dications had singlet ground states with deltaE(ST)/k(B) = -27 to -21 K for the m-isomer 3(2+) and with deltaE(ST)/k(B) = -10 to -8 K for the p-isomer 4(2+). Theoretical calculation of the exchange interaction J for these dications at the orthogonal torsion angle geometries was carried out for 3a2+ and 4a2+ and for (m- and p-phenylene)bisphenothiazine dications 1(2+) and 2(2+) using the broken-symmetry approach for the singlet states. A good correlation was observed between the calculated J and a MO-energy term in the triplet state, deltaE(TMO) = absolute value(HOMO(alpha) - (HOMO - 1)(alpha)). The calculated J values were negative in the order of 10 K for the m-dications (J/k(B) = -14.7 K for 1(2+), -11.5 K for 3a(2+)), but much smaller negative values were found for the p-isomers (J/k(B) = -0.9 K for 2(2+), -0.8 K for 4a2+). The smaller absolute value(J) values for the p-dications are qualitatively consistent with the experimental deltaE(ST) (2J) values.
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Affiliation(s)
- Eriko Terada
- Department of Chemistry, Graduate School of Science, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
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Wang T, Krylov AI. The effect of substituents on electronic states’ ordering in meta-xylylene diradicals: Qualitative insights from quantitative studies. J Chem Phys 2005; 123:104304. [PMID: 16178594 DOI: 10.1063/1.2018645] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Equation-of-motion spin-flip coupled-cluster method with single and double substitutions (EOM-SF-CCSD) is employed to study how substituents affect the electronic states' ordering in meta-xylylene diradicals. The electronegativity of substituents and the incorporation of a heteroatom are found to have a negligible effect. The effect of charges on energy gaps is much more pronounced, in agreement with the proposal of Dougherty and co-workers [J. Am. Chem. Soc. 118, 1452 (1996)]. Resonance structure theory and molecular orbital analysis are employed to explain this phenomenon. The changes in the exocyclic C-C bond length in substituted meta-xylylenes, derived from equilibrium structures calculated by using analytic gradients for the EOM-SF-CCSD method, support the original resonance theory explanation by West et al. However, a similar resonance-theory-based reasoning fails to explain the quantitative difference between positively and negatively charged systems as well as the observed strong stabilization of an open-shell singlet state in the N-oxidized pyridinium analog of meta-xylylene.
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Affiliation(s)
- Tao Wang
- Department of Chemistry, University of Southern California, Los Angeles, 90089-0482, USA
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Suenaga Y, Pierpont CG. Binuclear Complexes of Co(III) Containing Extended Conjugated Bis(Catecholate) Ligands. Inorg Chem 2005; 44:6183-91. [PMID: 16124794 DOI: 10.1021/ic050250m] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Binuclear complexes of cobalt(III) have been prepared with 3,3',4,4'-tetrahydroxy-benzaldazine (H4thB), 3,3',4,4'-tetrahydroxy-5,5'-dimethoxybenzaldazine (H4thM), and 3,3',4,4'-tetrahydroxydimethylbenzaldazine (H4thA) as bis(catecholate) ligands that link metal ions separated by 16 A through a conjugated bridge. In one case, [Co2(bpy)4(thM)]2+, stereodynamic properties observed in solution by 1H NMR are associated with valence tautomerism, with formation of a labile hs-Co(II) species by electron transfer from the catecholate regions of the bridge. Electrochemical oxidation of the complexes occurs at the bridges as two closely spaced one-electron couples. Chemical oxidation of [Co2(bpy) 4(thB)]2+ with Ag+ is observed to occur as a two-electron process forming [Co2(bpy) 4(thB(SQ,SQ))]4+. Attempted crystallization in the presence of air was observed to result in formation of the [Co(bpy)2(BACat)]+ (H2BACat, 3,4-dihydroxybenzaldehyde) cation by aerobic oxidation. Structural characterization is provided for the H4thM ligand and [Co(bpy)2(BACat)](BF4).
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Affiliation(s)
- Yusaku Suenaga
- Department of Chemistry, Kinki University, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan.
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Catala L, Le Moigne J, Gruber N, Novoa JJ, Rabu P, Belorizky E, Turek P. Towards a better understanding of magnetic interactions within m-phenylene alpha-nitronyl nitroxide and imino nitroxide based radicals, part III: Magnetic exchange in a series of triradicals and tetraradicals based on the phenyl acetylene and biphenyl coupling units. Chemistry 2005; 11:2440-54. [PMID: 15674973 DOI: 10.1002/chem.200400552] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The present work completes and extends our previous reports on the determination of the magnetic ground state and on the strength of the through bond exchange coupling within series of biradicals. This knowledge was subsequently exploited for the analysis of the magnetic interactions in their crystals. We report here the studies of series of triradicals incorporating alpha-nitronyl nitroxides (NN) or alpha-imino nitroxides (IN) as terminal radical fragments connected through a m-phenylene coupling unit in one case and a phenyl acetylene unit in other case. Tetraradical derivatives have also been studied. The studies of isolated molecules (EPR in solution and DFT calculations) allow the assessment of the magnetic interactions through the magnetic coupling unit. All triradical derivatives are found to exhibit a quartet ground state, whereas a singlet ground state is determined for the tetraradical. This last result reinforces previous findings that the singlet ground state is favoured in related biradicals involving similar m-phenylene couplers. Moreover, the through bond magnetic exchange coupling for the ortho-meta connectivity could be demonstrated as being ferromagnetic, thus ascertaining our previous hypotheses. The magnetic properties of the triradicals and tetraradicals in their solid state have been rationalized by using a previously proposed methodology, allowing to identify the most relevant magnetic pathways.
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Affiliation(s)
- Laure Catala
- Institut de Chimie Moléculaire et des Matériaux d'Orsay bâtiment 420, Université Paris-Sud, 91120 Orsay, France
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Constantinides CP, Koutentis PA, Schatz J. A DFT Study of the Ground State Multiplicities of Linear vs Angular Polyheteroacenes. J Am Chem Soc 2004; 126:16232-41. [PMID: 15584760 DOI: 10.1021/ja045006t] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Unrestricted density functional calculations in combination with the broken-symmetry approach and spin-projection methods have been employed to study a series of formally 4n pi antiaromatic linear and angular polyheteroacenes. Calculations show that the linear polyheteroacene molecules have either stable singlet zwitterionic 6-9 or singlet diradical 5 ground states because they sacrifice the aromaticity of the central arene to form two independent cyanines. The corresponding angular compounds 10-14 have robust triplet states, since they cannot create independent cyanines to escape their overall antiaromaticity. An analysis based on the SOMO-SOMO energy splittings, their spatial distributions, and the spin density populations for the triplet states is presented to clarify the factors that determine their ground state multiplicities.
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Serwinski PR, Esat B, Lahti PM, Liao Y, Walton R, Lan J. Photolysis and Oxidation of Azidophenyl-Substituted Radicals: Delocalization in Heteroatom-Based Radicals. J Org Chem 2004; 69:5247-60. [PMID: 15287767 DOI: 10.1021/jo049500r] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
2-(4-Azidophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (14), 2-(4-azidophenyl)benzimidazole-1-oxide-3-oxyl (16), 2-(4-azidophenyl)-1,2,6-triphenylverdazyl (19), 2-(3-azidophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (21), and (3-azidophenyl)-N-tert-butyl-N-aminoxyl (25) were photolyzed in frozen solution to give S = 3/2 state ESR spectra of the corresponding nitrenophenyl radicals with the following zero-field splitting parameters: |D/hc| = 0.277 cm(-1), |E/hc| < or = 0.002 cm(-1) (7 from 14); |D/hc| = 0.256 cm(-1), |E/hc| < or = 0.002 cm(-1) (8 from 16); |D/hc| = 0.288 cm(-1), |E/hc| < or = 0.002 cm(-1) (9 from 19); |D/hc| = 0.352 cm(-1), |E/hc| = 0.006 cm(-1) (10 from 21); |D/hc| = 0.336 cm(-1), |E/hc| = 0.004 cm(-1) (11 from 25). UB3LYP/6-31G computations and ESR spectroscopic analyses suggest that these are nitreno radicals, even para-linked systems with possible quinonoidal resonance forms. Neat samples of azidophenyl radicals 14 and 21 showed bulk paramagnetic behavior, consistent with the lack of close contacts in their crystal structures. Efforts to make photolabile coordination complexes of 14 and 21 with paramagnetic transition metal ions were unsuccessful: Cu(ClO4)2 x 6H2O instead oxidized them to the corresponding diamagnetic nitrosonium perchlorate salts.
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Affiliation(s)
- Paul R Serwinski
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA
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Shultz DA, Fico RM, Bodnar SH, Kumar RK, Vostrikova KE, Kampf JW, Boyle PD. Trends in exchange coupling for trimethylenemethane-type Bis(semiquinone) biradicals and correlation of magnetic exchange with mixed valency for cross-conjugated systems. J Am Chem Soc 2003; 125:11761-71. [PMID: 13129381 DOI: 10.1021/ja0367849] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A magnetostructural correlation (conformational electron spin exchange modulation) within an isostructural series of biradical complexes is presented. X-ray crystal structures, variable-temperature electron paramagnetic resonance spectroscopy, zero-field splitting parameters, and variable-temperature magnetic susceptibility measurements were used to evaluate molecular conformation and electron spin exchange coupling in this series of molecules. Our combined results indicate that the ferromagnetic portion of the exchange couplings occurs via the cross-conjugated pi-systems, while the antiferromagnetic portion occurs through space and is equivalent to incipient bond formation. Thus, molecular conformation controls the relative amounts of ferro- and antiferromagnetic contributions to exchange coupling. In fact, the exchange parameter correlates with average semiquinone ring torsion angles via a Karplus-Conroy-type relation. Because of the natural connection between electron spin exchange coupling and electronic coupling related to electron transfer, we also correlate the exchange parameters in the biradical complexes to mixed valency in the corresponding quinone-semiquinone radical anions. Our results suggest that delocalization in the cross-conjugated, mixed-valent radical anions is proportional to the ferromagnetic contribution to the exchange coupling in the biradical oxidation states.
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Affiliation(s)
- David A Shultz
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, USA.
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