The addition of the paramagnetic reagents gadolinium(18- crown-6) nitrate, gadolinium(dicyclohexano-18-crown-6) nitrate, and gadolinium nitrate pentahydrate to each of the substrates ethylbenzene, and thymidine has been studied in an attempt to obtain quantitative 13C spectra. These reagents reduce the nuclear Overhauser effect and shorten the spin-lattice relaxation times of the carbons of these substrates
