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

Abstract

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 metalto-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. 29 AcO ─ ions (1 equiv.) and NO 3 ─ , Cl ─ , Br ─ , HSO 4 ─ , ClO 4 ─ , and PF 6 ─ ions (upto 5 equiv.) in CH 3 CN solution.Fig. 11 Stern-Volmer plot of [1](ClO 4 ) 2 with CN ─ .

Ruthenium-based PACT agents based on bisquinoline chelates: synthesis, photochemistry, and cytotoxicity

“…However, we did not notice during our investigations on [3] 2+ , any sign of deprotonation in aqueous solution near pH = 7.4, so that such arguments remain, at that moment, pure speculation. Another hypothesis is that hydrogen bonding involving the non-coordinated NH bridge and biological anions would lead to better transport of the complex through the cell membrane [50]. All in all, the difference in cellular toxicity between [1](PF 6 ) 2 on the one hand, and [2](PF 6 ) 2 and [3](PF 6 ) 2 on the other hand, probably come from other reasons than differences in cellular uptake.…”

Switchable Optical Probes for Simultaneous Targeting of Multiple Anions

“…Though pyrophosphate also induced a red coloration of the solution, unlike F − , it hosted within the cavity of the calix sensor. A similar type of ruthenium‐based anion sensing probes ( 17‐19 ) were reported by Das and coworkers for specific recognition of both cyanide and fluoride ion in acetonitrile medium . Here, CN − or F − , owing to their highly basic characteristics, could abstract the imidazolium −NH and modulate the charge transfer state of the metal complexes.In 2011, Bhattacharya et al .…”

“…A similar type of ruthenium-based anion sensing probes (17)(18)(19) were reported by Das and coworkers for specific recognition of both cyanide and fluoride ion in acetonitrile medium. [88] Here, CN À or F À , owing to their highly basic characteristics, could abstract the imidazolium À NH and modulate the charge transfer state of the metal complexes.In 2011, Bhattacharya et al developed a library of anthra[1, 2-d] imidazole-6,11-dione probes (20-23) in order to investigate the effect intramolecular charge transfer (ICT) on the extent of anion binding process. [89] Among the various anions, distinct color change was observed selectively with F À (yellow to blue, Δλ~120 nm) and CN À ion (yellow to red, Δλ~80 nm).…”

“…On the contrary, other triphosphates could only interact through their pyrophosphate chain (electrostatic interaction) and enhanced the possibility of pyrenepyrene excimer formation (as evidenced from the larger excimer emission). A similar type of Zinc(II)-BPA complex (88) was designed by Xing et al to achieve specific identification of three different adenine nucleotides (AMP, ADP and ATP). [173] Unlike the previous case, here pyrene-adenine-pyrene assembly was observed solely with ADP, while ATP preferred to interact through pyrophosphate chain.…”

Substituent‐Controlled Selective and Sensitive Potential Optical Fluoride Sensors Based on Salicylidene Schiff Base Derivatives

“…To the best of our knowledge, only a few receptors are reported which satisfy selectivity criteria ,. Previously, we have developed a sequential substitution redox series of mixed‐ligand mononuclear ruthenium(II) complexes which act as potential anion sensors selective to fluoride and cyanide ions . In past few years Schiff base molecules have drawn great attention as selective anion sensor as they involve simple synthetic route and can be finely modified as per requirement.…”