Platinum Pyrimidine Blues: Still a Challenge to Bioinorganic Chemists and a Treasure for Coordination Chemists

Abstract

A class of intensely colored platinum complexes, derived from the hydrolysis product of the antitumor agent cisplatin, cis-[Pt(NH3)2(H2O)2]2+, and pyrimidine nucleobases (pym) and related cyclic or open amides, and generally termed 'Platinum Blues', is discussed. First reported over 30 years ago, major questions concerning their nature have been solved since then, for example their mixed valency and paramagnetism. Their modes of action as antitumor agents and as nucleic acid stains remain elusive, however. It has generally been assumed that the 'Blues' adopt linear chain structures, thus permitting short Pt•••Pt contacts, but more recent findings demonstrate that these ligands also allow cyclic structures to be formed (metallacalix[n]arenes). They provide a wealth of interesting properties with regard to host–guest chemistry and non-covalent DNA binding. These developments are reviewed.