Abstract
Complex-formation equilibria involving trans-diamine palladium(II) (Pd
II
), 4,4′-bipyridine (bpy), and inosine were investigated at 25 °C and 0.1 M (NaNO
3
) ionic strength. The stability constants of all possible mono-nuclear and binuclear complexes were determined. The concentration distribution diagram for the binuclear complexes of Pd
II
-bpy-inosine reveals the complexes that predominate in the physiological pH range and the quite feasible interaction of the binuclear complex Pd
II
-bpy-Pd
II
with inosine as a DNA constituent. On the basis of DFT calculations (B3LYP/LANL2DZp), the structures of the investigated equilibrium species show typical bond lengths for Pd-O and Pd-N bonds. The C-C bond in [Pd(4,4′-bpy)(NH
3
)
2
(OH
2
)]
2+
is clearly shortened to 1.47 Å, leading to reduced aromaticity in bpy. Comparison with model compounds suggests that the uncoordinated aromatic ring can be understood as an electron donating group.