Inter- and intramolecular C-H⋯O bonding in the anions of 1,3-indandione derivatives

Mark Sigalov, Pnina Krief, Lev Shapiro, Vladimir Khodorkovsky

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Derivatives of a series of 1,3-indandione (1) self-condensation products (2-4) and their anions (2a-4a) were investigated by NMR and UV/Vis spectroscopy and quantum mechanical calculations. These compounds exhibit a number of unusual features in their NMR spectra. Parent compound 1 is nearly not ionized in DMSO, whereas 3 is ionized completely. In contrast, derivatives 2 and 4 undergo partial ionization in DMSO and interaction between the neutral and anionic species affords the anionic intermolecular complexes, which exhibit both temperature- and concentration-dependent NMR spectra. The NMR spectra of pure salts 2a and 3a are concentration independent, but temperature dependent. Charge derealization in anions 2a and 3a gives rise to restricted rotation over the partial double bonds connecting the indane fragments. Energies of barriers to rotation were estimated from the temperature dependence of the 13C NMR spectra. The intramolecular aromatic C-H⋯O hydrogen bonding found previously in 2-4 is also observed in corresponding anions 2a-4a.

Original languageEnglish
Pages (from-to)673-683
Number of pages11
JournalEuropean Journal of Organic Chemistry
Issue number4
DOIs
StatePublished - 12 Feb 2008

Keywords

  • Hydrogen bonds
  • Indandiones
  • Ionization

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