Synthesis, spectral characterization and cytotoxicity of Ru–bipyridyl complexes containing hexakis(pyrazol-1-yl)benzene (hpzb) as a co-ligand

A novel ruthenium bisbipyridine complex, [Ru(bpy)2(hpzb)](PF6)2 (1) (hpzb = hexakis(pyrazol-1-yl)benzene) was obtained in the reaction between [Ru(bpy)2Cl2], the tritopic ligand hpzb and NH4PF6. A high selectivity has been found in the reaction and when the hpzb ligand was made to react with more than one ruthenium fragment, it coordinated selectively only to the first metallic fragment, and it was not possible to introduce two or three ruthenium centres. A similar complex with a deuterated bipyridine has also been obtained. The reaction with the methylated ligand hexakis(3,5-dimethylpyrazol-1-yl)benzene does not take place. A complete assignment of all the proton and carbon NMR signals of 1 was carried out. The orientation of the free pyrazolyl groups is also discussed. The redox properties and the anticancer activity of complex 1 have been studied.

Graphical abstractThe new derivative [Ru(bpy)2(hpzb)](PF6)2 (1) (hpzb = hexakis(pyrazol-1-yl)benzene) was obtained selectively in the reaction between [Ru(bpy)2Cl2], hpzb and NH4PF6. A complete assignment of all the proton and carbon NMR signals was carried out. The orientation of the free pyrazolyl groups is discussed. The anticancer activity of 1 has been tested.Figure optionsDownload full-size imageDownload as PowerPoint slide