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Madeleine Koh


University of Texas at Austin, Chemistry, B.S.

University of Warwick, Analytical Science, M.Sc. (present)

Irradiated Osmium Complexes


Novel Photochemical Properties of Organometallic Osmium Arene Iodido Complexes


Cancer is one of the world’s leading causes of death, which makes research and development of effective cancer therapeutic drugs highly important. Following the effectiveness of a widely-used chemotherapy drug, cisplatin (cis-diamminedichloroplatinum(II)), there has been an increasing interest in developing similar compounds consisting of other platinum group elements. In particular, we are interested in osmium arene iodido complexes. Previous research has shown that osmium arene complexes can be cytotoxic to cancer cells1,2. Continuing from there, our research is interested in the use of photoactivated chemotherapy (PACT)3 and photodynamic therapy (PDT)4 techniques, in which inactive osmium arene complexes are activated by a specific wavelength of light in a desired location (i.e. the tumor). We are attempting to develop compounds that are stable and inactive in the dark, and only upon irradiation would they become active and produce cytotoxic effects. This would be beneficial in reducing unwanted toxic side effects, like those of cisplatin.

Various analytical techniques were employed to validate the presence of each chemical compound, reactions that were occurring, and the appearance of new products. Nuclear magnetic resonance (NMR) was used to determine the purity of the synthesized products. Electrospray mass spectrometry (ESI-MS) was predominantly used to determine the presence of the compound of interest and any newly formed products after irradiation. Liquid chromatography-mass spectrometry (LC-MS) was also used for this purpose. UV-Vis spectrophotometry was used to measure the absorbance over a range of wavelengths to monitor the photoreactions occurring during the course of irradiation.

1 van Rijt, S.; Mukherjee, A.; Pizarro, A.; Sadler, P. J. Med. Chem., 2010, 53 (2), 840-849.
Fu, Y.; Habtemariam, A.; Pizarro, A.; van Rijt, S.; Healey, D.; Cooper, P.; Shnyder, S.; Clarkson, G.; Sadler, P. J. Med. Chem., 2010, 53 (22), 8192-8196.
Farrer, N.; Salassa, L.; Sadler, P. Dalton Trans., 2009, 48, 10690-10701.
Yano, S.; Hirohara, S.; Obata, M.; Hagiya, Y.; Ogura, S.; Ikeda, A.; Kataoka, H.; Tanaka, M.; Joh, T. J. Photochem. Photobio. C: Photochem. Rev., 2011, 12, 46-67.

For more information, please visit the Sadler group site or contact me.