Syntheses of Fluorescent Vitamin B 12 -Pt(II) Conjugates and their Pt(II) Release in a Spectroelectrochemical Assay

The cisplatin adduct of vitamin B 12 , cis-[PtCl(NH 3 ) 2 B 12 ] + (1) reacts with dansyl-imidazole to form cis-[Pt(dansyl-imidazole)(NH 3 ) 2 B 12 ] (2). In a spectroelectrochemical assay, Co(III) in 2 was reduced to Co(II) under concomitant release of the Pt(II) complex. Since similar reduction occurs in the intracellular space, 2 can be used for studying cell uptake monitored by fluorescent microscopy. The insertion of a fluorescent marker into the platinum moiety will also facilitate the isolation of the platinum complex released from B 12 and therefore to characterize its chemical authenticity.