详细
We investigated the dynamic structure of benzalaniline derivatives, in which an important factor is the inhibited internal rotation of benzene rings. The parameters of conformational processes of this type are characterized based on NMR spectroscopy data and quantum mechanical calculations. In these compounds, nitrogen atoms play a key role. It has been shown that important information is provided by NMR parameters with the direct participation of nitrogen, which become available in experiments with 15N-enriched compounds. Important new information about the conformation of molecules of this class can be provided by the spin-spin interaction constants involving 15N nuclei. A series of [15N]enriched benzalaniline derivatives with substituents in the ortho position of the benzene ring distant from the nitrogen was studied. It has been shown that substituents can act as both a stabilizing (R = F, OH, OCH3) and a destabilizing factor (R = CH3). The influence of medium acidity on these conformational equilibria was studied. This type of structural motif can be used to design pH-induced molecular switches. According to our estimates, the molecular switching energy of [15N]-2-fluorobenzalaniline is ~7 kcal/mol, which is one of the highest values for molecular switches of this type.