Combined application of auto-correlated (COSY) and homonuclear J-resolved two-dimensional NMR spectra for the assignment of congested, non-first order spectra of polycyclic aromatic systems. Assignment of the ¹H-NMR spectrum of benzo[2,3]phenanthro-[4,5-bcd]thiophene and an investigation of long range ¹H-¹H spin-coupling constants

Total assignment of the proton nmr spectrum of benzo[2,3]phenanthro[4,5-bcd]thiophene at 200 MHz is reported. Preliminary identification of the resonances comprising the individual spin Systems was accomplished by the use of auto-correlated two-dimensional proton nmr spectroscopy (COSY). Individual assignments were made on the basis of spin-coupling information which was obtained from the “titled” two-dimensional J-resolved (2DJ) proton nmr spectrum of the title compound. Because of the greater resolving power of the latter experiment relative to conventional proton nmr spectroscopy, a number of long range inter-ring spincouplings were observed. The observation of these long range couplings was crucial to the final assignment of several of the resonances in the spectrum. Resonances due to strong coupling in the 2DJ spectrum were also shown to be a useful means of correlating strongly coupled spins which provides an alternative to the COSY spectrum for this purpose.