Tunable Arene Ruthenium Metallaprisms to Transport, Shield, and Release Porphin in Cancer Cells

International audienceThree neutral dinuclear p-cymene ruthenium complexes (1a–1c) of the general formula (p-cymene)2Ru2(μ4-L)Cl2, bridged by substituted hydroxybenzoquinonato spacers (La = 2,5-dihydroxy-3-phenyl-1,4-benzoquinonato; Lb = 2,5-dihydroxy-3,6-diphenyl-1,4-benzoquinonato; Lc = 2,5-dihydroxy-3,6-(3,5-dimethylphenyl)-1,4-benzoquinonato) have been synthesized and characterized. The corresponding p-cymene ruthenium metallaprisms, [{(p-cymene)2Ru2(μ4-L)}3(tpt)2][CF3SO3]6 (2a–2c), were obtained by mixing in methanol the neutral dinuclear complexes 1a–1c, AgCF3SO3, and 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine (tpt). In a similar fashion, addition of porphin during the formation of the metallaprisms afforded the host–guest systems [porphin⊂{(p-cymene)2Ru2(μ4-L)}3(tpt)2][CF3SO3]6 ([porphin⊂2][CF3SO3]6). The biological activity of all complexes was estimated on the colon cancer cell line HT-29, showing low cytotoxicity in the dark (IC50 > 5 μM). On the other hand, the phototoxicity of the porphin-in-the-cage systems under standard irradiation conditions (20 J/cm2) is quite spectacular, being in the lower nanomolar range for [porphin⊂2c][CF3SO3]6