Heterometallic BODIPY-Based Molecular Squares Obtained by Self-Assembly: Synthesis and Biological Activities

Metal-based multinuclear supramolecules with different functionalities designed by self-assembly represent a growing area of research due to their versatile applications, particularly as anticancer agents. Four novel boron dipyrromethene (BODIPY)-based octacationic heterometallic molecular squares, 3-6 were synthesized by self-assembly via reaction of dipyridyl BODIPY ligands with suitable 90° palladium and platinum acceptors. The formation of the as-synthesized molecular squares was confirmed by multinuclear NMR spectroscopy, elemental analysis, high resolution electrospray mass spectrometry, UV-vis spectroscopy, and fluorescence spectroscopy. The square molecular structures of 4 and 6 were further rationalized theoretically using the PM7 semi-empirical method. The activities of the supramolecules against cancer cells were tested using cell lines of various malignant and nonmalignant origins. Complexes 3-6 showed high cytotoxicity toward cancer cells but 7.0 to 15.2 times lower cytotoxic effects were observed against nonmalignant human kidney epithelial cells (HEK-293). Particularly, complexes 3-6 provided 2.1-6.0 times lower IC₅₀ values as compared to cisplatin in HCT116 cells. Interestingly, BDP ligand-containing complexes (3 and 4) induced cytotoxicity through apoptosis, whereas BDPCC-based complexes (5 and 6) induced cell death by necrosis. This study presents a novel series of iron-based heteroatomic palladium and platinum complexes that exhibit substantial potential as drug candidates for anticancer therapy.