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Viesser RV, Donald CP, May JA, Wu JI. Can Twisted Double Bonds Facilitate Stepwise [2 + 2] Cycloadditions? Org Lett 2024; 26:3778-3783. [PMID: 38684005 DOI: 10.1021/acs.orglett.4c00879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Computational studies for a series of low to high strain anti-Bredt alkenes suggest that those with highly twisted bridgehead double bonds and a small singlet-triplet energy gap may undergo facile stepwise [2 + 2] cycloadditions to furnish four membered rings. A selection of reaction substrates, including ethylene, acetylene, perfluoroethylene, and cyclooctyne are considered.
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Affiliation(s)
- Renan V Viesser
- Department of Chemistry, University of Houston, Houston, Texas 77204, United States
| | - Clayton P Donald
- Department of Chemistry, University of Houston, Houston, Texas 77204, United States
| | - Jeremy A May
- Department of Chemistry, University of Houston, Houston, Texas 77204, United States
| | - Judy I Wu
- Department of Chemistry, University of Houston, Houston, Texas 77204, United States
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2
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Haga N, Ishida T. A Triplet/Singlet Ground-State Switch via the Steric Inhibition of Conjugation in 4,6-Bis(trifluoromethyl)-1,3-phenylene Bisnitroxide. Molecules 2023; 29:70. [PMID: 38202653 PMCID: PMC10779647 DOI: 10.3390/molecules29010070] [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: 10/30/2023] [Revised: 12/12/2023] [Accepted: 12/19/2023] [Indexed: 01/12/2024] Open
Abstract
Ground triplet 4,6-bis(trifluoromethyl)-1,3-phenylene bis(tert-butyl nitroxide) (TF2PBN) reacted with [Y(hfac)3(H2O)2] (hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate), affording a doubly hydrogen-bonded adduct [Y(hfac)3(H2O)2(TF2PBN)]. The biradical was recovered from the adduct through recrystallization. Crystallographic analysis indicates that the torsion angles (|θ| ≤ 90°) between the benzene ring and nitroxide groups were 74.9 and 84.8° in the adduct, which are larger than those of the starting material TF2PBN. Steric congestion due to o-trifluoromethyl groups gives rise to the reduction of π-conjugation. Two hydrogen bonds enhance this deformation. Susceptometry of the adduct indicates a ground singlet with 2J/kB = -128(2) K, where 2J corresponds to the singlet-triplet gap. The observed magneto-structure relation is qualitatively consistent with Rajca's pioneering work. A density functional theory calculation at the UB3LYP/6-311+G(2d,p) level using the atomic coordinates determined provided a result of 2J/kB = -162.3 K for the adduct, whilst the corresponding calculation on intact TF2PBN provided +87.2 K. After a comparison among a few known compounds, the 2J vs. |θ| plot shows a negative slope with a critical torsion of 65(3)°. The ferro- and antiferromagnetic coupling contributions are balanced in TF2PBN, being responsible for ground-state interconversion by means of small structural perturbation like hydrogen bonds.
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Affiliation(s)
| | - Takayuki Ishida
- Department of Engineering Science, The University of Electro-Communications, Chofu 182-8585, Tokyo Prefecture, Japan
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Prajapati B, Ambhore MD, Dang DK, Chmielewski PJ, Lis T, Gómez-García CJ, Zimmerman PM, Stępień M. Tetrafluorenofulvalene as a sterically frustrated open-shell alkene. Nat Chem 2023; 15:1541-1548. [PMID: 37783726 PMCID: PMC10624625 DOI: 10.1038/s41557-023-01341-8] [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: 02/14/2023] [Accepted: 09/04/2023] [Indexed: 10/04/2023]
Abstract
Electronic and steric effects are known to greatly influence the structure, characteristics and reactivity of organic compounds. A typical π bond is weakened by oxidation (corresponding to the removal of electrons from bonding orbitals), by reduction (through addition of electrons to antibonding orbitals) and by unpairing of the bonding electrons, such as in the triplet state. Here we describe tetrafluorenofulvalene (TFF), a twisted, open-shell alkene for which these general rules do not hold. Through the synthesis, experimental characterization and computational analysis of its charged species spanning seven redox states, the central alkene bond in TFF is shown to become substantially stronger in the tri- and tetraanion, generated by chemical reduction. Furthermore, although its triplet state contains a weaker alkene bond than the singlet, in the quintet state its bond order increases substantially, yielding a flatter structure. This behaviour originates from the doubly bifurcated topology of the underlying spin system and can be rationalized by the balancing effects of benzenoid aromaticity and spin pairing.
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Affiliation(s)
| | | | - Duy-Khoi Dang
- Department of Chemistry, University of Michigan, Ann Arbor, MI, USA
| | | | - Tadeusz Lis
- Wydział Chemii, Uniwersytet Wrocławski, Wrocław, Poland
| | - Carlos J Gómez-García
- Departamento de Química Inorgánica and Instituto de Ciencia Molecular, Universidad de Valencia, Paterna, Spain
| | - Paul M Zimmerman
- Department of Chemistry, University of Michigan, Ann Arbor, MI, USA.
| | - Marcin Stępień
- Wydział Chemii, Uniwersytet Wrocławski, Wrocław, Poland.
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4
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Izod K, Liu M, Evans P, Wills C, Dixon CM, Waddell PG, Probert MR. Spontaneous Decomposition of an Extraordinarily Twisted and Trans-Bent Fully-Phosphanyl-Substituted Digermene to an Unusual Ge I Cluster. Angew Chem Int Ed Engl 2022; 61:e202208851. [PMID: 35946808 PMCID: PMC9804623 DOI: 10.1002/anie.202208851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Indexed: 01/05/2023]
Abstract
Ditetrelenes R2 E=ER2 (E=Si, Ge, Sn, Pb) substituted by multiple N/P/O/S-donor groups are extremely rare due to their propensity to disaggregate into their tetrylene monomers R2 E. We report the synthesis of the first fully phosphanyl-substituted digermene {(Mes)2 P}2 Ge=Ge{P(Mes)2 }2 (3, Mes=2,4,6-Me3 C6 H2 ), which adopts a highly unusual structure in the solid state, that is both strongly trans-bent and highly twisted. Variable-temperature 31 P{1 H} NMR spectroscopy suggests that 3 persists in solution, but is subject to a dynamic equilibrium between two conformations, which have different geometries about the Ge=Ge bond (twisted/non-twisted) due to a difference in the nature of their π-stacking interactions. Compound 3 undergoes unprecedented, spontaneous decomposition in solution to give a unique GeI cluster {(Mes)2 P}4 Ge4 ⋅5 CyMe (7).
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Affiliation(s)
- Keith Izod
- Main Group Chemistry LaboratoriesSchool of ChemistryNewcastle UniversityNewcastle upon TyneNE1 7RUUK
| | - Mo Liu
- Main Group Chemistry LaboratoriesSchool of ChemistryNewcastle UniversityNewcastle upon TyneNE1 7RUUK
| | - Peter Evans
- Main Group Chemistry LaboratoriesSchool of ChemistryNewcastle UniversityNewcastle upon TyneNE1 7RUUK
| | - Corinne Wills
- School of ChemistryNewcastle UniversityNewcastle upon TyneNE1 7RUUK
| | - Casey M. Dixon
- School of ChemistryNewcastle UniversityNewcastle upon TyneNE1 7RUUK
| | - Paul G. Waddell
- School of ChemistryNewcastle UniversityNewcastle upon TyneNE1 7RUUK
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Izod K, Liu M, Evans P, Wills C, Dixon CM, Waddell PG, Probert MR. Spontaneous decomposition of an extraordinarily twisted and trans‐bent fully‐phosphanyl‐substituted digermene to an unusual Ge(I) cluster. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202208851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Keith Izod
- University of Newcastle School of Chemistry Bedson Building NE1 7RU Newcastle upon Tyne UNITED KINGDOM
| | - Mo Liu
- Newcastle University School of Chemistry UNITED KINGDOM
| | - Peter Evans
- Newcastle University School of Chemistry UNITED KINGDOM
| | - Corinne Wills
- Newcastle University School of Chemistry UNITED KINGDOM
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Hirao Y, Hamamoto Y, Kubo T. Tunable Solid-State Thermochromism: Alkyl Chain Length-Dependent Conformational Isomerization of Bianthrones. Chem Asian J 2022; 17:e202200121. [PMID: 35388961 DOI: 10.1002/asia.202200121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 04/05/2022] [Indexed: 11/12/2022]
Abstract
The introduction of linear alkoxy chains into bianthrone promoted the aggregation of the minor twisted conformer and made it compete with the major folded conformer in the solid-state. Rapid evaporation approach to the methoxy- and n -butoxy-substituted derivatives provided powder mixtures of folded and twisted conformers as metastable solids. Upon heating the powders, different lengths of alkyl chains converged to different conformers via solid-state thermal reaction with an apparent color change. Monitoring by FT-IR spectroscopy and powder XRD ensured that these thermal reactions involve only conformational isomerization without pyrolysis. In addition, single crystal X-ray structure analysis revealed that twisted conformers with longer alkyl chains are stabilized in the solid-state by the synergistic effect of their inter-chain hydrophobic interactions and π-π stacking interactions.
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Affiliation(s)
- Yasukazu Hirao
- Osaka University: Osaka Daigaku, Department of Chemistry, Graduate School of Science, 1-1 Machikaneyama, 560-0043, Toyonaka, Osaka, JAPAN
| | - Yosuke Hamamoto
- Osaka University: Osaka Daigaku, Department of Chemistry, Graduate School of Science, 1-1 Machikaneyama, 5600043, Toyonaka, JAPAN
| | - Takashi Kubo
- Osaka University: Osaka Daigaku, Department of Chemistry, Graduate School of Science, 1-1 Machikaneyama, 5600043, Toyonaka, JAPAN
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Kundu A, Chandra S, Mandal D, Neuman NI, Mahata A, Anga S, Rawat H, Pal S, Schulzke C, Sarkar B, Chandrasekhar V, Jana A. Twisted Push-Pull Alkenes Bearing Geminal Cyclicdiamino and Difluoroaryl Substituents. J Org Chem 2021; 86:12683-12692. [PMID: 34473501 DOI: 10.1021/acs.joc.1c01201] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The systematic combination of N-heterocyclic olefins (NHOs) with fluoroarenes resulted in twisted push-pull alkenes. These alkenes carry electron-donating cyclicdiamino substituents and two electron-withdrawing fluoroaryl substituents in the geminal positions. The synthetic method can be extended to a variety of substituted push-pull alkenes by varying the NHO as well as the fluoroarenes. Solid-state molecular structures of these molecules reveal a notable elongation of the central C-C bond and a twisted geometry in the alkene motif. Absorption properties were investigated with UV-vis spectroscopy. The redox properties of the twisted push-pull alkenes were probed with electrochemistry as well as UV-vis/NIR and EPR spectroelectrochemistry, while the electronic structures were computationally evaluated and validated.
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Affiliation(s)
- Abhinanda Kundu
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, Telangana, India
| | - Shubhadeep Chandra
- Lehrstuhl für Anorganische Koordinationschemie, Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
| | - Debdeep Mandal
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, Telangana, India
| | - Nicolás I Neuman
- Lehrstuhl für Anorganische Koordinationschemie, Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany.,Instituto de Desarrollo Tecnológico para la Industria Química, CCT Santa Fe CONICET-UNL, Colectora Ruta Nacional 168, Paraje El Pozo, 3000 Santa Fe, Argentina
| | - Alok Mahata
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, Telangana, India
| | - Srinivas Anga
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, Telangana, India
| | - Hemant Rawat
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, Telangana, India
| | - Sudip Pal
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, Telangana, India
| | - Carola Schulzke
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Straße 4, D-17489 Greifswald, Germany
| | - Biprajit Sarkar
- Lehrstuhl für Anorganische Koordinationschemie, Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
| | | | - Anukul Jana
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, Telangana, India
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