The compound cis-[Pt(NH3)(4-aminoTEMPO)ClI] (7) is a paramagnetic analogue of the anticancer drug cisplatin and of cis-[Pt(NH3)(C6H11NH2)Cl-2] (1), a major metabolite of a recently developed, orally administered derivative. The bifunctional mixed amine complex 7 and a monofunctional triamine complex, trans-[Pt(NH3)(2)(4-aminoTEMPO)Cl]NO3 (8), were synthesized to provide localized unpaired electron spin density for use in NMR spectral studies of their polynucleotide adducts. Compounds 7 and 8 readily coordinate to the N(7) positions of guanosine nucleosides, as revealed by H-1, P-31, and Pt-195 NMR spectroscopy. The NMR spectra were selectively broadened owing to distance-dependent relaxation from the unpaired electron localized on the nitroxyl radical of the 4-aminoTEMPO ligand. Platination of d(GpG) by the mixed amine complex 7 afforded two orientational isomers which differed with respect to the positioning of the 4-aminoTEMPO group toward either the 3’ or 5’ side of the phosphodiester linkage. The purified orientational isomers were readily distinguished by selective broadening of the H-1 NMR resonances of the 3’ and 5’ deoxyribose rings.