Märkl, Gottfried and Hafner, Markus and Kreitmeier, Peter and Stadler, Christian and Daub, Jörg and Nöth, Heinrich and Schmidt, Martin and Gescheidt, Georg (1997) A first example of a porphyrinoid fulvalene: Synthesis, structure, ESR and electrochemical investigations. HELVETICA CHIMICA ACTA, 80 (8). pp. 2456-2476. ISSN 0018-019X, 1522-2675
Full text not available from this repository.Abstract
The macrocyclic tetraepoxy-1H-[21]annulen-1-one 4 can by synthesized by the cyclizing Wittig reaction of 5,5'-carbonylbis[furan-2-carbaldehyde] (11) and the bisphosphonium salt 12, obtained from 2,2'-bifuran-5,5'-dicarboxaldehyde (13). According to an X-ray structure analysis, the annulenone 4 is not planar in the crystal; the H-1-NMR spectra of 4 reveal an averaged planarity with respect to the NMR timescale. The McMurry reaction of 4 yields fulvalene 3 in 43 % yield as the most expanded fulvalene hithertoo known. The X-ray structure analyses of 3 surprising establishes a 'syn'-orientation of the two rings with respect to the central C=C bond, thus forming a basket-like molecule. The H-1-NMR spectrum confirms the averaged planarity of both macrocycles in 3. CV and spectroelectrochemical measurements of 3 suggest a reversible two-electron reduction producing dianion 15 with two aromatic, anionic Sa,15a-didehydro-10H-21,22,23,24-tetraoxa-5a,15a-dihomocorrole (= tetraoxa[22]porphyrin(2.1.2.0)) ring systems containing 22 pi electrons each. The formation of 15 can also be achieved chemically by reaction of 3 with metallic potassium. The dication 16 of 3 may be antiaromatic, but the exact electronic structure is dubious. ESR and ENDOR investigations on the radical cation and the radical anion of 3 indicate that the free electron is delocalized in the entire molecule.
| Item Type: | Article |
|---|---|
| Additional Information: | Autor ist in WoS falsch geschrieben /gup |
| Uncontrolled Keywords: | 5 REDOX STAGES; UV/VISIBLE/NEAR-IR; MO; PENTAFULVALENE; DICATION |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Organische Chemie > Alumni or Retired Professors > Prof. Dr. Jörg Daub |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 24 May 2023 09:15 |
| Last Modified: | 24 May 2023 09:15 |
| URI: | https://pred.uni-regensburg.de/id/eprint/51194 |
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