1H NMR Spectra of Ternary Platinum(II) Complexes with N-Ethyl- or N-Benzyl-1,2-ethanediamine and 2,2'-Bipyridine or 1,10-Phenanthroline. Intramolecular Aromatic-Aromatic Interaction in Coordination Sphere, and It's Solvent and Temperature Effects.

Square-planar complexes with the formula [Pt(L-1) (L-2)]X-2. where L-1 is di(ammine) or 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) and L-2 is N-ethyl-1,2-ethanediamine (Eten) or N-benzyl-1,2-ethanediamine (Been), and X = NO3 or Cl-, were prepared. NMR measurements of D2O solutions of these complexes showed that the N-ethyl and N-benzyl groups are forced to take a pseudo axial disposition due to an intramolecular repulsion from hydrogen atoms of aromatic diamines for complexes where L-1 = bpy or phen and significant upfield shifts due to the ring current effect were observed for the Been complexes. An analysis of coupling with N-H and Pt-195 showed that the major rotamer due to rotation around CH2-NH is (-)-syn for the Been with a significant intramolecular stacking between aromatic rings of L-1 and L-2, but anti-for the Eten complexes. The solvent and temperature dependency of the upheld shift of the Been complexes are described; the protein denaturants, guanidinium chloride, and urea, act to reduce stacking as dioxane.