Correspondence between INEPT and DEPT pulse sequences for coupled spin-half nuclei

A correspondence is derived between the extended INEPT sequence for polarization transfer from n equivalent protons to a spin-half nucleus I and the DEPT sequence. This allows a calculation of the optimum variable pulse angle and enhancement value for the coupled and decoupled DEPT spectra of the group IHn, and enables us to show that the coupled DEPT spectra are distortion-free for all values of n. These results are checked experimentally for specific values of n. The correspondence relies on a trigonometrical operator relation which does not hold for spin I greater than a half, making the DEPT and INEPT sequences quite distinct for higher spins.