Alkynyl Ruthenium Colorimetric Sensors: Optimizing the Selectivity toward Fluoride Anion

Highly selective acetate optical sensing of a ruthenium(II) complex carrying imidazole and indole groups

The effects of addition of F(-), Cl(-), Br(-), I(-), NO(3)(-), H(2)PO(4)(-), and OAc(-) on the UV-vis and emission spectra of Ru(II) complex [Ru(bpy)(2)(H(2)iip)](ClO(4))(2) {bpy=2,2'-bipyridyl, H(2)iip=2-indole-3-yl-imidazole[4,5-f][1,10]-phenanthroline} in dimethyl sulfone were studied. The Ru(II) complex was evidenced to be a highly selective optical sensor for OAc(-). Addition of OAc(-) elicited a distinct change in color from yellow to light orange which can be detected by naked-eye, and an almost vanished emission of the Ru(II) complex at a much lower concentration of OAc(-) than those of the other anions.

A novel fluorescent and colorimetric anion sensor based on thiourea derivative in competitive media

A novel and simple fluorescent receptor bearing thiourea moiety as recognition site was described. The recognition behavior of the receptor toward different anions was investigated in DMSO/H2O (95:5 v/v) and dry DMSO through two various channels: the colorless-yellow color change and a remarkable enhancement of the fluorescence. And the enhancement of the fluorescence was attributed to an anion-induced increase of the rigidity of the host molecule.

Detailing hydrogen bonding and deprotonation equilibria between anions and urea/thiourea derivatives

Spectrophotometric and 1H NMR titrations of N-methoxyethyl-N'-(4-nitrophenyl)thiourea (3) by Bu(4-)NOAc show that in DMSO deprotonation of the receptor and formation of a hydrogen-bonded complex with anion proceed simultaneously but in MeCN deprotonation requires the participation of the second acetate anion. The formation constants of hydrogen-bonded complexes were determined from titrations in the presence of added acetic acid, which suppressed deprotonation. These constants together with independently measured stability constants of (AcO)(2)H(-) complexes were employed for a rigorous numerical analysis of titration results in the absence of added acid, which allowed us to determine the equilibrium deprotonation constants as well as pKa values for 3 in both solvents. Although 3 appeared to be a weaker acid than AcOH in both solvents, it can be deprotonated by acetate in dilute solutions when the concentration of liberated acetic acid is low enough. With disubstituted N,N-bis(methoxyethyl)-N'-(4-nitrophenyl)thiourea 4 only deprotonation equilibrium is observed. In contrast, both parent urea derivatives 1 and 2 cannot be deprotonated by acetate anions. Independent of the real type of equilibrium, whether it is a deprotonation or a hydrogen bonding, titration plots always can be satisfactorily fitted to a formal 1:1 binding isotherm. A relationship between apparent "binding constants" and real equilibrium constants of hydrogen bonding association and deprotonation processes is discussed.