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Inter‐ and Intramolecular C–H···O Bonding in the Anions of 1,3‐Indandione Derivatives
Author(s) -
Sigalov Mark,
Krief Pnina,
Shapiro Lev,
Khodorkovsky Vladimir
Publication year - 2008
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200700684
Subject(s) - chemistry , intramolecular force , delocalized electron , nmr spectra database , hydrogen bond , crystallography , intermolecular force , carbon 13 nmr , proton nmr , ionization , protonation , nuclear magnetic resonance spectroscopy , carbon 13 nmr satellite , spectral line , computational chemistry , photochemistry , stereochemistry , ion , fluorine 19 nmr , organic chemistry , molecule , physics , astronomy
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 delocalization 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 13 C NMR spectra. The intramolecular aromatic C–H ··· O hydrogen bonding found previously in 2 – 4 is also observed in corresponding anions 2a – 4a .(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)