Toward the Design of Novel Polynuclear Platinum Antitumor Complexes: A Polydentate Ligand System Based on Dipyridylamine and 1,3,5Trimethylenebenzene

A novel hexadentate ligand, N,N,Nʹ,Nʹ,Nʹ ʹ,Nʹ ʹ-hexa(2-pyridyl)-1,3,5-tris(aminomethyl)benzene (L), was designed and synthesized. The X-ray structure analysis reveals that the three dipyridylamine (DPA) groups of L are almost perpendicular to the central trimethylenebenzene, and two of them are spacially close to each other while the third one is further apart. The trinuclear Pt(II) complexes [Pt3LCl6] (1) and [Pt3L(CBDCA)3] (2) (where CBDCA represents cyclobutane dicarboxylic acid) were prepared and fully characterized by IR, NMR, and ESMS spectroscopy. A mononuclear complex, [PtL (CBDCA)] (3), was also prepared and structurally characterized, which suggests that controlled formation of mono-, di-, and trinuclear complexes with L is possible. Spectroscopic data showed that complexes 2 and 3 are able to bind to calf thymus DNA and their CBDCA group can be readily replaced by thiourea.