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A set of metal carbonyl cluster-boronic acid conjugates of the group VIII metals (Fe, Ru, and Os) were synthesized and their antiproliferative effects measured against two breast cancer cell lines (MCF-7 and MDA-MB-231) and a noncancerous breast epithelial (MCF-10A) cell line. The cytotoxicity followed the order Ru > Os > Fe for the MDA-MB-231 cells, although the latter two exhibited similar cytotoxicity against MCF-7 and MCF-10A cells. The osmium species {Os3(CO)10(μ-H)[μ-SC6H4-p-B(OH)2]} (2) could be chemically oxidized to its hydroxy analogue [Os3(CO)10(μ-H)(μ-SC6H4-p-OH)] (2-OH), which showed comparable cytotoxicity. Mode of action studies pointed to an apoptotic pathway for cell death. Ministry of Education (MOE) Nanyang Technological University Published version This work was supported by Nanyang Technological University and the Ministry of Education (Research grant no. RG121/18).

High nuclearity carbonyl clusters of ruthenium and osmium are found to exhibit good photoacoustic (PA) activity in the near-IR (NIR) region. Their potential as PA contrast agents for full body imaging has been demonstrated for the first time with mice; intravenous administration of the osmium carbonyl cluster Na-2[Os-10(mu(6)-C)(CO)(24)] afforded up to a four-fold enhancement of the PA signal in various tissues. The cluster exhibits low toxicity, high stability and superior PA stability compared to the clinically approved NIR dye, indocyanine green.

The ruthenacyclic carbamoyl complexes [RuBr(2-NHC(O)C5H3N-4-R)(CO)2(MeCN)] in which the 4-position of the pyridinyl ring is derivatized, have been synthesized. These are ruthenium-based structural mimics of the natural [Fe]-hydrogenase metal cofactor. The derivative with R = H reacts with phosphine to form a disubstituted product [RuBr(2-NHC(O)C5H4N)(CO)(PPh2SPh)2].

Conjugates of organometallic osmium carbonyl clusters and gold nanoparticles show a strong carbonyl signal in surface-enhanced Raman spectroscopy. The ease of bio-functionalization and the high stability and good dispersibility in aqueous solution make these conjugates excellent candidates for biomedical applications, as demonstrated by live-cell imaging with the carbonyl signals of OM-NP(PEG)-L conjugates.