Encapsulation of hydrophobic pyrenyl­cycloplatinate complexes within a water-soluble arene ruthenium metalla­cage

Two hydrophobic pyrenyl-containing cycloplatinate complexes {2­(1-pyrenyl)pyridine}Pt(acac) (Pt-1) and {2-(4-(1-pyrenyl)phenyl)pyridine}Pt(acac) (Pt-2) (acac = acetylacetonato) have been encapsulated in the hexacationic water-soluble metalla-cage [(p-cymene)6Ru6(donq)3(tpt)2]6 + (donq = 5,8-dioxydo-1,4-naphthoquinonato, tpt = 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine). The host–guest systems [(Pt-1)⊂cage]6 + and [(Pt-2)⊂cage]6 + have been characterized by NMR and UV-visible spectroscopy, thus confirming the encapsulation of the platinum complexes in the hexa-ruthenium metalla-cage. In addition, the cytotoxicities of the complex-in-a-complex systems have been established using human ovarian A2780 and A2780cisR cancer cell lines. This study shows IC50 values in the lower micromolar range for both compounds and on both cancer cell lines (IC50 ≈ 1 μM): These values being higher than the empty metalla-cage which possesses an IC50 > 3 μM. This amplified overall cytotoxicity for the complex-in-a-complex systems suggests an efficient delivery of the hydrophobic complexes by the water-soluble arene ruthenium metalla-cage.

Graphical abstractTwo hydrophobic pyrenyl-containing cycloplatinate complexes have been encapsulated in a hexacationic water-soluble metalla-cage. The cytotoxicities of the complex-in-a-complex systems have been established and it shows IC50 values in the lower micromolar range (IC50 ≈ 1 μM). These values suggest an efficient delivery of the hydrophobic Pt-complexes by the water-soluble arene ruthenium metalla-cage.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Preparation of hexacationic water-soluble ruthenium metalla-cage. ► Encapsulation of pyrenyl-containing cycloplatinate complex in the cavity of metalla-cage. ► Enhancement of cytotoxicity for the complex-in-a-complex systems. ► Higher activity than cisplatin.