Cisplatin analogues with 2,2′-dipyridylamine ligands and their reactions with DNA model nucleobases

Six novel platinum(II) and palladium(II) complexes with — cisplatin — analogous configuration were prepared and could be obtained as single crystals for X-ray structure analyses. The ligand system based on 2,2′-dipyridylamine was extended stepwise by adding alkyl chains to the bridging nitrogen atom, starting from pure 2,2′-dipyridylamine to (2,2′-dipyridyl)-n-butylamine. In the case of [Pt(dpa)Cl2] and [Pt(dpma)Cl2] the reaction of the hydrolyzed complexes with the model nucleobases 1-methylthymine and 1-methyluracil, respectively, was studied. The resulting Pt(II)–dpa–methylthyminato and Pt(II)–dpa–dpma–methyluracilato complexes could also be characterized by X-ray diffraction. The platinum compounds form dinuclear complexes with the model nucleobases, acting as secondary bridging ligands via their N3 and O4 donor atoms. Bis(μ-1-methylthyminato-N3-O4)bis[2,2′-dipyridylamineplatinum(II)] hexafluorophosphate nitrate perchlorate dihydrate (10) (triclinic, space group P) contains the model nucleobases in a head-to-head orientation, whereas bis(μ-1-methyluracilato-N3-O4)[2,2′-dipyridylamineplatinum(II)][(2,2′-dipyridyl)methylamineplatinum(II)] hexafluorophosphate nitrate trihydrate (11) (monoclinic, space group P21/c) contains the model nucleobases in a head-to-tail orientation. The dynamic behavior of [Pt(dpea)(H2O)2]2+ and the coordination of the model nucleobase 1-methylthymine in solution were studied by 195Pt NMR spectroscopy.