| Abstract: | The preparation, characterisation and 1H NMR spectra of some N-arylaminopropenylylidenearylammonium salts are reported. The NMR data show that in DMSO the cations exist as conjugated amino–imines, generally as the ‘all-trans’ geometrical isomer. An exception is found in the case of the 4-nitrophenyl derivative which produces a mixture of the ‘all-trans’ and ‘cis-trans’ isomers with slow exchange between them at room temperature. The relative stability of the ‘all-trans’ isomer increases as the salt becomes more ionic. By varying the temperature, pH and nature of the anion it is found that exchange of the N? H protons on the cation controls the appearance of spin-spin coupling between the N? H and 1,3-propene protons. |
