Synthesis and characterization of ion pairs between alkaline metal ions and anionic anti-aromatic and aromatic hydrocarbons with π-Conjugated central seven- And eight-membered rings

Jan Bloch, Stefan Kradolfer, Thomas L. Gianetti, Detlev Ostendorf, Subal Dey, Victor Mougel, Hansjörg Grützmacher

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

The synthesis, isolation and full characterization of ion pairs between alkaline metal ions (Li+, Na+, K+) and mono-anions and dianions obtained from 5H-dibenzo[a,d]cycloheptenyl (C15H11 = trop) is reported. According to Nuclear Magnetic Resonance (NMR) spectroscopy, single crystal X-ray analysis and Density Functional Theory (DFT) calculations, the trop- and trop2−• anions show anti-aromatic properties which are dependent on the counter cation M+ and solvent molecules serving as co-ligands. For comparison, the disodium and dipotassium salt of the dianion of dibenzo[a,e]cyclooctatetraene (C16H12 = dbcot) were prepared, which show classical aromatic character. A d8-Rh(I) complex of trop was prepared and the structure shows a distortion of the C15H11 ligand into a conjugated 10π -benzo pentadienide unit—to which the Rh(I) center is coordinated—and an aromatic 6π electron benzo group which is non-coordinated. Electron transfer reactions between neutral and anionic trop and dbcot species show that the anti-aromatic compounds obtained from trop are significantly stronger reductants.

Original languageEnglish (US)
Article number4742
JournalMolecules
Volume25
Issue number20
DOIs
StatePublished - Oct 2020
Externally publishedYes

Keywords

  • Alkali metals
  • Aromaticity
  • Cyclooctatetraene ions
  • Density functional theory (DFT)
  • Electrochemistry
  • Electron paramagnetic resonance (EPR) spectroscopy
  • Ion pairs
  • Rhodium
  • Tropylidenyl ions

ASJC Scopus subject areas

  • Analytical Chemistry
  • Chemistry (miscellaneous)
  • Molecular Medicine
  • Pharmaceutical Science
  • Drug Discovery
  • Physical and Theoretical Chemistry
  • Organic Chemistry

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