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Three new selective anion receptors containing the (thio)urea binding sites were developed, Indole-3-formaldehyde phenyl-semithiocarbazone, Indole-3-formaldehyde nitrophenyl-semithiocarbazone, and Indole-3-formaldehyde nitrophenyl-semicarbazone, nominated as receptors 1, 2 and 3, respectively. Receptor 1 shows high selective recognition for F only, while both receptor 2 and receptor 3 containing a p-nitro group show high selective recognition for AcO. The high selective recognition of these receptors to anions is further investigated by X-ray crystallography diffraction, UV-vis, fluorescence analyses and H NMR. Furthermore, receptor 2 changes from yellow to orange, and receptor 3 darkens when acetate is added, providing a way of detection by 'naked-eye'. [ABSTRACT FROM AUTHOR]

novel artificial anion chemosensor 1 based on 2, 2′-di (4-nitrophenylurea-β- N-yl) -1, 1′-binaphthyl is designed and synthesized for sensing anions including halide ions and oxoanions. The fluorescent emission of the binaphthyl of receptor 1, forming the hydrogen bonding with anions as the sensing mechanism, is monitored in DMSO for detecting anions. In brief, while most of the anion chemosensors are switch-off fluorescent chemosensor, or non-fluorescent sensor, receptor 1 exhibits obviously the switch-on emission during the complexation with HPO. [ABSTRACT FROM AUTHOR]

The kinetics of the acid-catalysed dissociation of CuII complexes of four N, N′-dialkyl-1,10-phenanthroline-2,9-dimethanamine ligands (alkyl = Me, Et, i-Pr, t-Bu) have been studied using a stopped-flow spectrophotometer in 6.6 × 10−3 ∼ 0.5 mol dm−3 HCl ( I = 0.5 mol dm−3 HCl + NaCl) over a range of temperatures. The kinetic data can be fitted to the rate expression kobs = k K′ 2[H+]/(1 + K′ 2[H+]). The acid dissociation can be rationalized in terms of a six-step kinetic process involving rapid pre-equilibrium cleavage of the two CuII–N(aliphatic amine) bonds, two rapid pre-equilibrium protonations and rate-determining cleavage of the CuII–N(phenanthroline) bond. The temperature dependence of the rate was determined and the appropriate thermodynamic parameters obtained. [ABSTRACT FROM AUTHOR]

The hydrolysis kinetics of p-nitrophenyl acetate (NA) catalyzed by CuII, ZnII and CoII complexes of tris(2-benzimidazylmethyl)amine (NBT) have been studied. The hydrolysis rate is first-order in both metal(II) complex and NA. The second-order rate constants, kcat are 0.083, 0.241 and 0.285 mol−1Ls−1 (298 K, I = 0.10 molL−1 KNO3, 0.02 molL−1 tris buffer, 40% MeCN aqueous solution) for Zn–NBT, Co–NBT and Cu–NBT complexes, respectively. The result indicates that the hydrolytic metalloenzyme activity of different metal complexes increases with the electrophilicity of the metal ions and that the complexes, in this paper, constitute that most efficient hydrolytic metalloenzyme models reported to date. An increase in MeCN content in the solution greatly reduces the hydrolytic activity of the nucleophiles. [ABSTRACT FROM AUTHOR]

Two hexadentate compounds incorporating 1,10-phenanthroline and four alkylamino donors have been prepared. The protonation constants and the formation constants of dipositive ion (Mn2+, Co2+, Cu2+ and Zn2+) complexes have been determined in aqueous solution by pH titration at 25 ± 0.1 °C and I = 0.1 mol·dm−3 NaNO3. [ABSTRACT FROM AUTHOR]