Synthesis, structural characterisation and luminescent anion sensing studies of a Ru(II)polypyridyl complex featuring an aryl urea derivatised 2,2′-bpy auxiliary ligand

The inclusion of a urea functionality into the coordination sphere of a Ru(II)-polypyridyl complex (Ru·L1) resulted in a system that can function as an effective long wavelength emissive fluorescent anion sensor. The MLCT emission of Ru·L1 is sensitive to the binding of acetate, phosphate and pyrophosphate but not fluoride in organic solvent. In addition, Ru·L1 can distinguish between phosphate and pyrophosphate with an emission increase upon binding of H 2 PO 4 - (“turn on” sensor) and an emission decrease upon binding of HP 2 O 7 3 - (“turn off” sensor), which occurs via hydrogen bonding to the urea receptor moiety as demonstrated by carrying out NMR titrations as well as by employing [Ru(II)bpy3] ( PF 6 - ) 2 as a model compound that lacks the anion receptor moiety.