On the Heterogeneous Nature of Cisplatin-1-Methyluracil Complexes: Coexistence of Different Aggregation Modes and Partial Loss of NH₃ Ligands as Likely Explanation.

ABSTRACT: The conversion of the 1?:?1-complex of Cisplatin with 1-methyluracil (1MeUH), cis-[Pt(NH₃ )₂ (1MeU-N3)Cl] (1?a) to the aqua species cis-[Pt(NH₃ )₂ (1MeU-N3)(OH₂ )]⁺ (1?b), achieved by reaction of 1?a with AgNO₃ in water, affords a mixture of compounds, the composition of which strongly depends on sample history. The complexity stems from variations in condensation patterns and partial loss of NH₃ ligands. In dilute aqueous solution, 1?a, and dinuclear compounds cis-[(NH₃ )₂ (1MeU-N3)Pt(?-OH)Pt(1MeU-N3)(NH₃ )₂ ]⁺ (3) as well as head-tail cis-[Pt₂ (NH₃ )₄ (?-1MeU-N3,O4)₂ ]²⁺ (4) represent the major components. In addition, there are numerous other species present in minor quantities, which differ in metal nuclearity, stoichiometry, stereoisomerism, and Pt oxidation state, as revealed by a combination of ¹ H NMR and ESI-MS spectroscopy. Their composition appears not to be the consequence of a unique and repeating coordination pattern of the 1MeU ligand in oligomers but rather the coexistence of distinctly different condensation patterns, which include ?-OH, ?-1MeU, and ?-NH₂ bridging and combinations thereof. Consequently, the products obtained should, in total, be defined as a heterogeneous mixture rather than a mixture of oligomers of different sizes. In addition, a N₂ complex, [Pt(NH₃ )(1MeU)(N₂ )]⁺ appears to be formed in gas phase during the ESI-MS experiment. In the presence of Na⁺ ions, multimers n of 1?a with n=2, 3, 4 are formed that represent analogues of non-metalated uracil quartets found in tetrastranded RNA.

SUBMITTER: Pullen S 

PROVIDER: S-EPMC7809254 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature