The photocytotoxicity of a series of anticancer trans-dihydroxido [Pt(N 3 ) 2 (OH) 2 (NH 3 )(X)] (X = alkyl or aryl amine) platinum(IV) diazido complexes has been examined and the influence of cistrans isomerism investigated. A series of photoactivatable Pt IV -azido complexes has been synthesized: the synthesis, characterisation and photocytotoxicity of six mixed-ligand ammine/ amine Pt IV diazido complexes, cis,trans,cis,-[Pt(N 3 ) 2 (OH) 2 (NH 3 )(X)] where X = propylamine (4c), butylamine (5c), pentylamine (6c) and aromatic complexes X= pyridine (7c) 2-methylpyridine (8c), 3-methylpyridine (9c) are reported. Six all-trans isomers have also been studied where X = methylamine (2t), ethylamine (3t), 2-methylpyridine (8t), 4-methylpyridine (10t), 3-methylpyridine (9t) and 2-bromo-3-methylpyridine (11t). All the complexes exhibit intense azide-to-Pt IV LMCT bands (ca. 290 nm for trans and ca. 260 nm for cis). When irradiated with UVA light (365 nm) the Pt IV complexes undergo photoreduction to Pt II species, as monitored by UV-vis spectroscopy. The trans isomers of complexes containing aliphatic or aromatic amines were more photocytotoxic than their cis isomers. One of the cis complexes (9c) was nonphotocytotoxic despite undergoing photoreduction. Substitution of NH 3 ligands by MeNH 2 or EtNH 2 results in more potent photocytotoxicity for the all-trans complexes. The complexes were all non-toxic towards human keratinocytes (HaCaT) and A2780 human ovarian cancer cells in the dark, apart from the 3-methylpyridine (9t) 2-bromo-3-methylpyridine (11t) and 4-methylpyridine (10t) derivatives.

Reactions of [Pt(rac‐1,2‐DACH)Cl2], [Pt(1R,2R‐DACH)Cl2] and the anticancer drug oxaliplatin with the tripeptide glutathione and glutathione disulfide have been studied by HPLC, ESI‐MS and NMR methods. The same two major products are formed in each reaction: a thiolate‐bridged dimer and a novel thiolate‐bridged dinuclear macrochelate containing a nine‐membered chelate ring. Redox reactions of PtII anticancer drugs with biological disulfides are of potential importance to their mechanism of action. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)