The cation−π interaction and the hydrophobic effect are important intermolecular forces in chemistry and play major roles in controlling recognition in biological systems. We compared their relative contributions to the binding of molecular “dumbbell” guests in synthetic container hosts in water. The guests offered direct, intramolecular competition between trimethylammonium groups, −N⁺(CH₃)₃, and tert-butyl groups, −C(CH₃)₃, for the internal surfaces (aromatic panels) of the containers. In contrast with previous studies, the container molecules consistently preferred binding to the uncharged tert-butyl groups, regardless of the presence of anionic, cationic, or zwitterionic groups on the container peripheries. This preference is determined by solvation of the polar trimethylammonium group in water, which outcompetes the attraction between the positive charge and the π-surfaces in the container. The synthetic container complexes provide a direct measure of the relative strengths of cation−π interactions and desolvation in water. Interactions with the uncharged tert-butyl group are more than 12 kJ mol^–1 more favorable than the cation−π interactions with the trimethylammonium group in these cavitand complexes.

A series of novel Pt(II) complexes [cis- and trans-Pt(II)(salicylaldimine)(DMSO)Cl (C-1), trans-Pt(II)(salicylaldimine)(4-picoline)Cl (C-2), Pt(II)(salicylaldimine)Cl (C-3), trans- and cis/trans-Pt₂(II)(salicylaldimine)(DMSO)₂Cl₂ (C-4), trans-Pt₂(II)(salicylaldimine)(4-picoline)₂Cl₂ (C-5) was synthesized and characterized. The structures of C-1-cis, C-1-trans and C-3 were determined using a single crystal X-ray analysis. This class of Pt(II) complexes has been studied for their in vitro cytotoxicity in multiple human cancer cell lines, including breast (MCF-7), liver (HepG2), lung (A549), colon (HCT116) and cervical (Hela) cancers. C-1-trans, C-2 and C-4-trans showed significant cytotoxicity to these cancer cells comparable to cisplatin. A time- and dose-dependent MTT assay revealed that these complexes can suppress cell viability and cell proliferation. Mechanistically these complexes induced pro-apoptotic gene expression such as BAX, PUMA and NOXA and thereby enhanced apoptosis. Moreover, PARP cleavage in a dose-dependent manner indicated their cytotoxic effect against cancer cells. Apoptosis of cancer cells occurred through apoptotic pathways as explained by the cytometry analysis. The DNA unwinding properties of these active Pt(II) complexes were studied by gel electrophoresis using pBR322 plasmid DNA as a target. Changes in the morphology of cancer cells were also observed upon the addition of C-1-trans, C-2 and C-4-trans.