Nitrogen-15 NMR of cis-diamine-platinum(II) complexes in aqueous solution

Samples were prepared and /sup 15/NMR spectra recorded for aqueous solutions of cis-(/sup 15/NH/sub 3/)/sub 2/Pt(H/sub 2/O/sub 2//sup 2 +/(1), /sup 15/N-en Pt(H/sub 2/O)/sub 2//sup 2 +/(3)(N-en = 100% /sup 15/N-labeled-ethylene-diamine), and for derivatives of 1 and 3 in which one or both of the water molecules are replaced by 100% /sup 15/N-labeled-1-methylimidazole (/sup 15/N-Me-Im). Such replacement produces a large change in both the /sup 15/N chemical shift and on the /sup 195/Pt-/sup 15/N coupling constant for the /sup 15/NH/sub 3/ or /sup 15/N-en nitrogens. At the same time, the /sup 15/N resonanes for both /sup 15/N/sub 1/ and /sup 15/N/sub 3/ of the /sup 15/N-MeIm are shifted from their positions in an aqueous solution of /sup 15/N-MeIm, and both resonances display satellites due to /sup 195/Pt-/sup 15/N coupling. These results indicate that /sup 15/N NMR is a sensitive probe for detecting interactions between cis-diamine-Pt(II)/sup 2 +/ species and imidazole-ring nitrogen in biological systems. 1 figure, 1 table.