Synthesis, structure and antiproliferative activity of organometallic iridium(III) complexes containing thiosemicarbazone ligands

In Vitro and In Vivo of Triphenylamine-Appended Fluorescent Half-Sandwich Iridium(III) Thiosemicarbazones Antitumor Complexes

Half-sandwiched structure iridium(III) complexes appear to be an attractive organometallic antitumor agents in recent years. Here, four triphenylamine-modified fluorescent half-sandwich iridium(III) thiosemicarbazone (TSC) antitumor complexes were developed. Because of the "enol" configuration of the TSC ligands, these complexes formed a unique dimeric configuration. Aided by the appropriate fluorescence properties, studies found that complexes could enter tumor cells in an energy-dependent mode, accumulate in lysosomes, and result in the damage of lysosome integrity. Complexes could block the cell cycle, improve the levels of intrastitial reactive oxygen species, and lead to apoptosis, which followed an antitumor mechanism of oxidation. Compared with cisplatin, the antitumor potential in vivo and vitro confirmed that Ir4 could effectively inhibit tumor growth. Meanwhile, Ir4 could avoid detectable side effects in the experiments of safety evaluation. Above all, half-sandwich iridium(III) TSC complexes are expected to be an encouraging candidate for the treatment of malignant tumors.

Novel half-sandwich rhodium(III) and iridium(III) photosensitizers for dual chemo- and photodynamic therapy

BACKGROUND AND OBJECTIVE

Photodynamic therapy has emerged as a promising treatment for cancer and other malignancies. Design of photosensitizers with two different action mechanisms may be an essential strategy for the improvement of the efficacy of phototherapeutic drugs. The objective of this study was to evaluate the anticancer photo- and chemocytotoxic effects of the novel half-sandwich rhodium(III) and iridium(III) photosensitizers.

MATERIALS AND METHODS

A series of novel half-sandwich Cp*-Rh(III) and Cp*-Ir(III) complexes containing 9-anthraldehyde thiosemicarbazones, (Cp*)M(L)Cl (M = Rh or Ir, L = 9-anthraldehyde thiosemicarbazones), were compared for cell uptake and photo- and chemocytotoxic effects against human prostate carcinoma (PC3) and human ovarian carcinoma (SKOV3) cell lines.

RESULTS

Cp*-Ir(III) complexes, (Cp*)Ir(L)Cl, showed remarkable phototoxic behavior against human ovarian adenocarcinoma SKOV3 cells (IC₅₀ = 2.7 and 2.3 μM, respectively, λ_irr > 400 nm), as well as the 7.4 and 5.3-fold lower toxicity in the dark, implying possibility of dual action as chemo- and phototherapeutic agents.

CONCLUSION

The complexes, which present a synergistic effect with good properties of both the Cp*-Rh(III) and Cp*-Ir(III) chemotherapeutic effect and the anthracene photodynamic therapy efficiency, show great potential as a new generation of light activated dual-action anticancer agents for photodynamic therapy.

Half-Sandwich Arene Ruthenium(II) and Osmium(II) Thiosemicarbazone Complexes: Solution Behavior and Antiproliferative Activity

We report the synthesis, characterization, and antiproliferative activity of organo-osmium(II) and organo-ruthenium(II) half-sandwich complexes [(η6-p-cym)Os(L)Cl]Cl (1 and 2) and [(η6-p-cym)Ru(L)Cl]Cl (3 and 4), where L = N-(2-hydroxy)-3-methoxybenzylidenethiosemicarbazide (L1) or N-(2,3-dihydroxybenzylidene)-3-phenylthiosemicarbazide (L2), respectively. X-ray crystallography showed that all four complexes possess half-sandwich pseudo-octahedral "three-legged piano-stool" structures, with a neutral N,S-chelating thiosemicarbazone ligand and a terminal chloride occupying three coordination positions. In methanol, E/Z isomerization of the coordinated thiosemicarbazone ligand was observed, while in an aprotic solvent like acetone, partial dissociation of the ligand occurs, reaching complete displacement in a more coordinating solvent like DMSO. In general, the complexes exhibited good activity toward A2780 ovarian, A2780Cis cisplatin-resistant ovarian, A549 lung, HCT116 colon, and PC3 prostate cancer cells. In particular, ruthenium complex 3 does not present cross-resistance with the clinical drug cisplatin in the A2780 human ovarian cancer cell line. The complexes were more active than the free thiosemicarbazone ligands, especially in A549 and HCT116 cells with potency improvements of up to 20-fold between organic ligand L1 and ruthenium complex 1.