文摘
A diplatinum(II) complex was prepared from a new 1,2-dithienylethene-based ligand containing N-methylimidazole groups as metal-binding units. Reaction of the ligand 1,2-bis[2-methyl-5-(1-methyl-1H-imidazol-2-yl)-3-thienyl]-cyclopentene (L2<sup>Hsup>) with cis-dichlorobis(dimethylsulfoxido)platinum(II) generated the bimetallic complex trans-[Pt<sub>2sub>Cl<sub>4sub>(DMSO)<sub>2sub>(L2<sup>Hsup>)] (DMSO = dimethyl sulfoxide), whose DNA-interacting properties were investigated using different techniques. Cytotoxicity assays with various cancer cell lines showed that this compound is active, with IC<sub>50sub> values in the micromolar range. Surprisingly, the diplatinum(II) complex does not exhibit the anticipated photoswitching properties; indeed, UV irradiation does not lead to the photocyclization of the ligand L2<sup>Hsup> or of the metal complex. Computational studies were performed and revealed significant differences in the electronic structure of L2<sup>Hsup> compared with L1<sup>Hsup> (i.e., 1,2-bis[2-methyl-5-(4-pyridyl)-3-thienyl]-cyclopentene, which exhibits photoswitching properties), in terms of the relevant molecular orbitals involved in the UV–vis absorption features, which ultimately is responsible for the inertia of L2<sup>Hsup> toward photocyclization.