A series of new 7-azaindolyl palladium and platinum complexes have been prepared. The X-ray structure determinations of [NBu(4)][M(C(6)F(5))(2)(Haza-N7)(aza-N1)].Haza [M = Pd, Pt; aza = 7-azaindolate (lH-pyrrolo[2,3-b]pyridinate)] have established for the first time the coordination to the same metal centre of both neutral and anionic forms of the ligand. Theoretical calculations at the mPW1B95/aug6-31G**/StRSCecp level show that both kinetic and thermodynamic arguments support the observed coordination and H-bonding interaction of the pyrrolo and pyridine moieties of the neutral and deprotonated heterocyclic ligands. At 48 h incubation time the new platinum complex [Pt(dmba)(aza-N1)(DMSO)] (dmba = N,N-dimethylbenzylamine-kappaN,kappaC) shows sub-micromolar activity both in A2780 and T47D [IC(50) (microM) = 0.34 and 0.53, respectively]. The DNA adduct formation of the new platinum complexes was followed by circular dichroism and electrophoretic mobility.