SOLUTION EQUILIBRIA OF THE TERNARY COMPLEXES OF [PD(DIEN)CL](-ACETYL AMINO-ACIDS() AND [PD(TERPY)CL](+) WITH NUCLEOBASES AND N)

Stability constants of the ternary palladium(ll) complexes of triamine s (diethylenetriamine(dien) and 2,2':6',2 ''-terpyridine(terpy)) and n ucleobases (1-methylcytosine(MeC), 9-methyladenine (MeA), 1-methylurac il(MeUH), 1-methylthymine(MeTH), 9-ethylguanine(EtGH), uridine, inosin e) or derivatives of amino acids (N-acetylhistamine(Ac-Hm), N-acetylhi stidine(Ac-His) and N-acetyllysine(Ac-Lys)) were determined by pH-metr ic titrations. Binding sites of the ligands in the ternary complexes w ere elucidated by H-1-nuclear magnetic resonance spectroscopy. It was found that all ligands form stable adducts with [Pd(terpy)](2+) and [P d(dien)](2+), except the [Pd(terpy)CI](+)/Ac-Lys system, where the for mation of the mixed hydroxo complex [Pd(terpy)(OH)](+) predominates. T he formation of dinuclear complexes of [Pd(terpy)](2+) and [Pd(dien)]( 2+) was identified with Ac-Hm and Ac-His (imidazole-N3/N1) and inosine and EtGH (purine-N1/N7), The [Pd(terpy))(2)LH-1](3+) dinuclear specie s were detected in slightly acidic media in the ternary systems contai ning MeC or MeA, in which one of the [Pd(terpy)](2+) units is bonded t o N3 of MeC or NI of MeA, while the second palladium(II) is coordinate d by the deprotonated exocyclic amino groups of the ligands. (C) 1997 Elsevier Science Inc.