Paramagnetic ring current in the diazepine ring of the 1H-benzo-1,5-diazepinium monocation

The signals of all of the protons in the PMR spectrum of 2,4-dimethyl-1H-benzo-1,5-diazepine hydrochloride are shifted to stronger fields by 0.5–1.0 ppm relative to the signals of the analogous protons in model compounds. This shift is explained by the considerable paramagnetic contribution of the eight π electrons of the diazepine ring of the 1H-benzo-1,5-diazepinium monocation to the magnetic susceptibility of the molecule. Calculations of the π-electron ring current and the π-electron component of the magnetic susceptibility of this monocation by the MO LCAO method showed that the ring current in the seven-membered ring is paramagnetic and depends markedly on the magnitude of the coulombic integral for nitrogen.