Deuterium NMR and Ab Initio Studies of Strongly Hydrogen-Bonded Molecules

Abstract

Two newly synthesized alkylated cyanomalonaldehyde derivatives possess very short intramolecular hydrogen bonds, which are studied by deuterium NMR. Both the dimethyl and di- tert-butyl derivatives have small deuterium quadrupole coupling constants and large asymmetry parameters. In addition, the di- tert-butyl compound, which has one of the shortest O– D…O hydrogen bonds yet measured, has a quadrupole coupling which anomalously increases with temperature. The significance of these phenomena is explored using a theoretical model which employs vibrationally averaged ab initio electric field gradient tensors calculated with large basis sets and electron correlation via the multiconfigurational self-consistent field method.