The first platinum(IV) complexes involving aromatic cytokinins or cyclin-dependent kinase inhibitors derived from 6-benzylaminopurine: X-ray structures of (BohH22+)[PtCl6]·H2Oand(RosH22+)2[PtCl6]Cl2·4H2O

A series of Pt(IV) complexes with cytokinins or CDK-inhibitors derived from 6-benzylaminopurine (Bap) of the composition [PtIV(LH+)Cl5] (1–14), where LH+ stands for protonated form of the Bap derivative (1–12), Boh = 6-(benzylamino)-2-[(3-hydroxypropyl)amino]-9-isopropylpurine, bohemine (13) and Ros = 6-(benzylamino)-2-[(1-hydroxymethylpropyl)amino]-9-isopropylpurine, roscovitine (14), have been prepared.They have been fully characterized by microanalysis, conductivity, FT-IR, 1H, 13C, 15N and 195Pt NMR and ES+ mass spectroscopy.It has been found that the cytokinin molecule is coordinated via N9 atom to platinum(IV) and N1, N7-protonated in case of complexes 1–12, and N7 coordinated and N1-protonated in case of complexes with CDK inhibitors (13 and 14).Predicted molecular geometries of the complexes have been supported by DFT calculations at the B3LYP level with the 6-311+G∗∗/LANL2DZ and aug-cc-pVDZ/LANL2DZ basis sets.All of the compounds have been tested in vitro for their cytotoxicity against four human cancer cell lines: malignant melanoma (G361), osteogenic sarcoma (HOS), chronic myelogenous erythroleukemia (K562) and breast adenocarcinoma (MCF7).The best result has been achieved for complex 14, where IC50 = 17 μM against K562. The molecular structures of two ionic pair compounds (BohH22+)[PtCl6]·H2O(15)and(RosH22+)2[PtCl6]Cl2·4H2O(16) have been determined by a single crystal X-ray analysis.

Graphical abstractA series of the first Pt(IV) complexes, involving a protonated form of cytokinin or CDK-inhibitor (Bohemine or Roscovitine) derived from 6-benzylaminopurine, of the type [PtIV(LH+)Cl5] (1–14) {where LH+ stands for the protonated form of the organic molecule} have been prepared and fully characterized by different physical methods.Geometries of representative complexes have been optimized by DFT calculations.The molecular structures of (BohH22+)[PtCl6]·H2O(15)and(RosH22+)2[PtCl6]Cl2·4H2O(16) have been determined by a single X-ray analysis.The complexes have been also screened in vitro for their cytotoxicity against selected human cancer cell lines.Figure optionsDownload full-size imageDownload as PowerPoint slide