Low barrier hydrogen bonds in sterically modified Schiff bases
- 6 March 2002
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 4,p. 835-842
- https://doi.org/10.1039/b106145n
Abstract
Five derivatives of an ortho-hydroxy Schiff base (2-(N-alkyl-α-iminoethyl)phenols) with very short intramolecular hydrogen bonds (dO(H)⋯N ≤ 2.500 Å) were synthesised. The crystal structures were determined. The steric repulsion of the substituted methyl group results in an unusual strengthening of the hydrogen bonds, decreasing the barrier for the proton movement within the hydrogen bridge, which leads to a delocalization of the proton position. The very strong influence of the character of the substituent in the phenol ring as well as the character of the N-alkyl chain on the proton distribution is demonstrated for these hydrogen bonds from the so-called inversion range.Keywords
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