The directed synthesis of organometallic cage molecules for the assembly of molecular nano-objects is a topical area of chemical research.[1] By combining the "molecular clip" strategy developed by Stang [2] with the "molecular paneling" strategy pioneered by Fujita, [3] we recently synthesized trigonal-prismatic cage molecules in which six (h 6 -arene)ruthenium or (h 5 -pentamethylcyclopentadienyl)rhodium units are held together by two trigonal 2,4,6-tris(pyridin-4-yl)-1,3,5-triazine (tpt) panels and three dichloro [4] or oxalato [5] (Figure 1). [7] The structure shows the [Pt(acac) 2 ] complex to be held between the triazine units of the tpt ligands. It is clear from the van der Waals representation of the "complex-in-a-complex" cation that the Pt(acac) 2 complex is indeed encapsulated in 1 6+; the separation between platinum and triazine-centroid being 3.4 . The {Ru 2 - Centre is gratefully acknowledged. M = Pd, Pt; acac = acetylacetonato; tpt = 2,4,6-tris(pyridin-4-yl)-1,3,5-triazine; dhbq = 2,5-dihydroxy-1,4-benzoquinonato.

Five 5,10,15,20-tetra(4-pyridyl)porphyrin (TPP) areneruthenium(II) derivatives and a p-cymeneosmium and two pentamethylcyclopentadienyliridium and -rhodium analogues were prepared and characterized as potential photosensitizing chemotherapeutic agents. The biological effects of all these derivatives were assessed on human melanoma tumor cells, and their cellular uptake and intracellular localization were determined. All molecules, except the rhodium complex which was not cytotoxic, demonstrated comparable cytotoxicity in the absence of laser irradiation. The ruthenium complexes exhibited excellent phototoxicities toward melanoma cells when exposed to laser light at 652 nm. Cellular uptake and localization microscopy studies of [Ru 4(eta (6)-C 6H 5CH 3) 4(TPP)Cl 8] and [Rh 4(eta (5)-C 5Me 5) 4(TPP)Cl 8] revealed that they accumulated in the melanoma cell cytoplasm in granular structures different from lysosomes. The fluorescent porphyrin moiety and the metal component were localized in similar structures within the cells. Thus, the porphyrin areneruthenium(II) derivatives represent a promising new class of organometallic photosensitizers able to combine chemotherapeutic activity with photodynamic therapeutic treatment of cancer.

Cationic arene ruthenium-based tetranuclear complexes comprising rectangular structures have been obtained from the dinuclear arene ruthenium complexes [Ru 2 (arene) 2 (OO∩OO) 2 Cl 2 ](arene= p-cymene, hexamethylbenzene; OO∩OO=2,5-dihydroxy-1,4-benzoquinonato, 2,5-dichloro-1,4-benzo-quinonato) by reaction with pyrazine or bipyridine linkers (N∩N=pyrazine, 4,4 0 -bipyridine, 1,2-bis(4-pyridyl)ethylene) in methanol in the presence of AgO 3 SCF 3 , forming tetranuclear cations of general for-mula [Ru 4 (arene) 4 (N∩N) 2 (OO∩OO) 2 ] 4þ . All complexes were isolated in good yield as triflate salts and were characterized by NMR and IR spectroscopy and studied by cyclic voltammetry. The cytotoxicities of the water-soluble compounds of the 4,4 0 -bipyridine and 1,2-bis(4-pyridyl)ethylene series have been established using ovarian A2780 cancer cells. The large rectangles incorporating 1,2-bis(4-pyridyl)-ethylene linkers are ca. 5 times more cytotoxic (IC 50 e 6 μM) than the 4,4 0 -bipyridine-containing cations (IC 50 g 30 μM). Structural characterization by X-ray diffraction of two representative compounds, i.e., the triflate salts of [Ru 4 (hexamethylbenzene) 4 (4,4 0 -bipyridine) 2 (2,5-dihydroxy-1,4-benzoquinonato) 2 ] 4þ and [Ru 4 (hexamethylbenzene) 4 (1,2-bis(4-pyridyl)ethylene) 2 (2,5-dichloro-1,4-benzoquinonato) 2 ] 4þ ,re-veals differently sized cavities, different flexibilities, and different packing arrangements, suggesting a correlation between these structural properties and the observed cytotoxicities.