Cyclens chemosensors

Cyclenes are a useful component of metal sensor molecules. The common structure of such chemosensor is fluorophore - linker - sensor. Various fluorophores were connected to the cyclene which ensured the detection of the desired cation. These molecules were often water soluble and worked under physiological conditions what made them interesting from the biomedical point of view. 

Kikuchi et al. reported a cyclen-Cd complex containing 7-amino-4-trifiuorocumarin 34 as a fiuorogenic chemosensor [52]. During the complexation of 34 with phosphates, the coordination bond of the aromatic amino group of the coumarin to Cd was cleaved, causing a dual-change of the excitation spectrum (Scheme 10). The dissociation constant of 34-nucleotide... 

Gunnlaugsson et al. isolated the luminescent diaqua Eu " and Tb " complexes with cyclens 55 [135]. The X-ray analysis revealed that cyclen 55b worked as a heptadentate ligand. These non-chromophoric complexes were photophysically silent upon excitation at 300 nm, but their Tb " complexes displayed characteristic emissions via highly coordinated complex-ation with chromophoric salicylate anion. The excited coordinated sah-cylate anion sensitized the lanthanide center, and luminescence enhancement factors of ca. 680 and 220 were observed with the two Tb " complexes. Since acetylsalicylate anion gave no sensitization, both complexes worked as effective chemosensors for salicylate anion under physiological conditions. 

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