Design, synthesis and applications of cation and anion sensing selective Ru(II)- Polypyridyl complexes have attracted a considerable attention because of their multipurpose and promising biological insinuation. Ruthenium(II)-polypyridyl ligands such as 2,2-bipyridine (bpy), 1,10-phenanthroline (phen), and/ or ortho-phenanthroline etc. on reaction with Ru(II) forms Ru(II)-polypyridyl complexes which have various significant benefits like metal-to-ligand charge transfer based on excited visible light and emission intensity, high chemical and photochemical stabilities, high shifts in Stokes (particularly more than 150 nm), greater response efficiency, low cytotoxicity and good water solubility. Owing to the MLCT emission, Ru(II) polypyridyl complexes were mostly used as essential materials in electro-generated chemiluminescence analysis offers unique properties like high rigidity, selectivity and less sensitive to environment. The multifaceted nature of Ru(II) polypyridyl-complexes in sensing is found as electrochemical sensors, solid state sensors, amperometric sensors, and straightforward chemosensors. A methodical report of different Ru(II) polypyridylcomplex chromophores emphasizing fluorophore frame work has been thoroughly discussed in this chapter. The binding mechanism has been proposed precisely. Unlike other metal complexes, the versatility and uniqueness of Ru(II) polypyridyl-complexes as chemosensor is observed in sensing of less common analytes which are rarely detected according to the literature. Polypyridyl Ru(II)-complexes being covalently bonded with photo conducting polymer may also be used as photosensitizers.
Keywords: Anions, Cations, Chemosensor, Colorimetric sensor, Fluorescence sensor, Hazardous metal ions, Molecular probe, Phosphorescence, Sensitive and selective sensor, MLCT, Ru(II)-polypyridyl complexes.