Fluorescent chemosensors containing a Ru(tpy)₂²⁺ core and open-chain polyazaalkanes

4′-[4-(Bromomethyl)phenyl]-2,2′:6′,2″-terpyridine reacts with triethylenetetraamine or tetraethylenepentaamine in CH₂Cl₂ to yield the ligands L¹ and L², respectively. Reaction of L¹ and L² with Ru(mtpy)Cl₃ (mtpy = 4′-methyl-2,2′:6′,2″-terpyridine) in MeOH yielded, after column chromatography and precipitation with [NH₄][PF₆], the compounds [Ru(L¹)(mtpy)][PF₆]₂ and [Ru(L²)(mtpy)][PF₆]₂. These metallo-receptors contain triethylenetetraamine or tetraethylenepentaamine recognition sites and [Ru(tpy)₂]²⁺ cores as fluorescent signalling subunits. The fluorescent behaviour of [Ru(L¹)(mtpy)]²⁺ and [Ru(L²)(mtpy)]²⁺ in the presence of metal ions and anions has been studied in MeCN:H₂O (70:30 v/v) as a function of the pH.