Bis-Olefin Based Crystalline Schlenk Hydrocarbon Diradicals with a Triplet Ground State |
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Authors: | Priyanka Saha Dr Nicolas Chrysochos Dr Benedict J Elvers Sebastian Pätsch Sk Imraj Uddin Dr Ivo Krummenacher Dr Muneshwar Nandeshwar Anshika Mishra Prof Karthik V Raman Prof Gopalan Rajaraman Prof Ganesan Prabusankar Prof Dr Holger Braunschweig Dr Prince Ravat Prof Dr Carola Schulzke Dr Anukul Jana |
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Institution: | 1. Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad, 500046 India;2. Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Straße 4, 17489 Greifswald, Germany;3. Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany;4. Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, 502284 India;5. Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400 076 India;6. Institute of Organic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany |
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Abstract: | A modular approach for the synthesis of isolable crystalline Schlenk hydrocarbon diradicals from m-phenylene bridged electron-rich bis-triazaalkenes as synthons is reported. EPR spectroscopy confirms their diradical nature and triplet electronic structure by revealing a half-field signal. A computational analysis confirms the triplet state to be the ground state. As a proof-of-principle for the modular methodology, the 4,6-dimethyl-m-phenylene was further utilized as a coupling unit between two alkene motifs. The steric conjunction of the 4,6-dimethyl groups substantially twists the substituents at the nonbonding electron bearing centers relative to the central coupling m-phenylene motif. As a result, the spin delocalization is decreased and the exchange coupling between the two unpaired spins, hence, significantly reduced. Notably, 108 years after Schlenk's m-phenylene-bis(diphenylmethyl) synthesis as a diradical, for the first time we were able to isolate its derivative with the same spacer, i.e. m-phenylene, between two radical centers in a crystalline form. |
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Keywords: | Alkenes Conjugation Radicals Schlenk Hydrocarbon Structure Elucidation |
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