Potential anion sensing properties by a redox and substitution series of [Ru(bpy)3?n(Hdpa)n]2+, n = 1–3; Hdpa = 2,2′-dipyridylamine: selective recognition and stoichiometric binding with cyanide and fluoride ions

摘要

Three mononuclear ruthenium complexes of composition [Ru(bpy) _(3? n ) (Hdpa) _( n ) ] ~(2+) , n = 1–3, where bpy = 2,2′-bipyridine, and Hdpa = 2,2′-dipyridylamine have been developed for selective recognition of cyanide (CN ~(?) ) and fluoride (F ~(?) ) ions. All the complexes have been characterised using standard analytical and spectroscopic techniques. The potential anion sensing features of complexes [ 1 ](ClO _(4) ) _(2) , [ 2 ](ClO _(4) ) _(2) and [ 3 ](ClO _(4) ) _(2) have been thoroughly investigated by spectrophotometry, electrochemistry and ~(1) H NMR spectroscopy using a wide variety of anions, such as F ~(?) , Cl ~(?) , Br ~(?) , PF _(6) ~(?) , NO _(3) ~(?) , ClO _(4) ~(?) , HSO _(4) ~(?) , AcO ~(?) and CN ~(?) . Cyclic voltammetry and differential pulse voltammetry established that [ 1 ](ClO _(4) ) _(2) and [ 2 ](ClO _(4) ) _(2) are excellent electrochemical sensors for the selective recognition of CN ~(?) and F ~(?) anions. The complexes display intense ligand-centred absorption bands in the UV region and moderately intense metal-to-ligand charge-transfer (MLCT) bands in the visible region. All the complexes act as selective colorimetric sensors for CN ~(?) and F ~(?) anions due to modulation of MLCT band position of the receptors in the presence of CN ~(?) or F ~(?) resulting distinct colour change visible by naked eyes. Further, emission quenching of 1 ~(2+) and 2 ~(2+) in the presence of CN ~(?) , F ~(?) and AcO ~(?) ions make them suitable luminescence-based sensors. The Stern–Volmer plot revealed static quenching mechanism of emission of the receptor 1 ~(2+) in presence of cyanide and fluoride ions, while dynamic quenching dominates in case of AcO ~(?) anion.