Synthesis and anion recognition of acetate ions using pyrrole-⍺-carboxaldehyde 2,4-dinitrophenyl hydrazone

1437-1439A pyrrol-based anion receptor (1) for acetate ions has been designed and synthesized. The receptor has been characterized by various chemical methods. Anion binding studies have been carried out using ¹H NMR and UV-vis spectra. The results indicate that deprotonation takes place after receptor 1 binds CH3COO. 1 exhibits high selectivity for acetate ions for complementarity between the receptor and anion. The compound may be useful in the field of sensor materials

Simple anion receptor with imidazole and phenol groups: Forming hydrogen-bond complex with Cl⁻

748-754A simple anion receptor 2'-(2"-hydroxy-3"-methoxyphenyl)imidazo[4',5'-f]-1, 10-phenanthroline[5,6-f] (1) with imidazole and phenol groups has been synthesized and its interaction investigated with anions (F⁻, Cr⁻, Br⁻, I⁻, AcO⁻ and H₂PO₄⁻) by UV -vis and ¹H NMR titrations. Added with Cl⁻, the change of UV -vis spectra of 1 is different from that of added AcO⁻,F⁻ and H₂PO₄⁻. Also, the change of ¹H NMR titration spectra of 1 with Cl⁻ is different from that of added AcO⁻, F⁻ and H₂PO₄⁻, 1 forms supramolecular complex with Cl⁻ as a receptor and is deprotonated with AcO⁻, F⁻ and H₂PO₄⁻ as a colormetric sensor. The receptor forms H-bond complex with Cl⁻ by NH of imidazole, Hc' of phenanthroline and H₁ of phenyl. As an acid proton donor, the protons of NH of imidazole and OH of phenol are too acidic to form hydrogen-bond complex with AcO⁻, F⁻ and H₂PO₄⁻. So, the interaction of 1 with AcO⁻, H₂PO₄⁻ and F⁻ is acid-basic reaction. The affinity to anions of NH is dramatically more powerful than that of OH

Multiple interactions in Zn(II) ternary systems of phenanthroline bridging polyaza ligand and adenosine, 5'-triphosphate

287-291The stability of Zn(II) ternary complexes of phenanthroline bridging polyaza ligand and ATP have been determined using potentiometric pH titrations, 1H and 31P NMR spectra. Protonated metal complexes interact with the polyphosphate chain of the nucleotide substrate by coordination, electrostatic and H-bonding interactions, as well as stacking interactions bctween the phenanthroline moiety of L and the nucleoside residue of ATP. Moreover, ion-π-donor, hydrophobic and even vander Waals interactions may exist in the ternary systems. The recognition of nucleotides is promoted by adding Zn(II) to the receptor/substrate system. Zn(II) acts as n "messenger" to bridge the polyamine and ATP, which in turn leads to competition between the mixed ligands in binding zinc ion. Thus, the supramolecules formed by self-assembly are good models to mimic the active center of the ATPase

Kinetics and mechanism of the dehydration of HCO₃^- catalyzed by Zn(II) and Cu(II) complexes of novel tripod ligand

1172-1175The observed rate constants of the dehydration reaction of HCO3- catalyzed by Zn(II) and Cu(II) complexes of novel tripod ligand have been measured both in 70% (v/v) alcohol solution and in aqueous solution by stopped-flow method. Reasonable explanation for the difference between the rate constants in 70% (v/v) alcohol solution and in aqueous solution has been proposed. The direction of reaction curve is changed in aqueous solution when the pH is greater than 7.6. The results are discussed and the mechanism is proposed

La(III) complex of phenanthroline bridging polyamine as efficient catalyst for the hydrolysis of ATP

1076-1080The hydrolysis of ATP catalyzed by protonated ligand 2, 9-di[(2'-ethylamino)ethylene-aminomethyl]-1, 10-phenanthroline·4HCl.H2O(L) or its La(III) complex has been studied at pH 7.6 using 31P NMR spectroscopy. The two systems have a rate of 12.1×10-4 mol.dm-3 and 159×10-4 mol.dm-3 , which is about 5- and 59-fold as fast as that of free ATP respectively. La(III) complex of L is a more efficient catalyst for ATP hydrolysis than metal ion alone, which has a rate enhancement ratio about 5. High catalytic efficiency has been achieved through the effective activation of ATP by La(III) complex and the availability of a good intramolecular nucleophile. The phosphoramidate intermediate at 2.88 ppm in L/ATP system has not been observed in La(III)/L/ATP system. The mechanism for ATP hydrolysis catalyzed by complex of ‘‘hard’’ metal ion has been given. The effects of metal ion mediated by polyaza ligand in controlling the recognition of the substrate and the attacking on phosphorous counter have been discussed

Kinetic and equilibrium studies of the acid dissociation of the zinc(II) complexes of N,N' -dialkyl-1, 10-phenanthroline-2,9-dimethanamine ligands

430-433The complexation property and the acid dissociation kinetics of the zinc(II) complexes of N,N' -dialkyl-1, 10-phenanthroline-2,9-dimethanamine ligands have been studied using pH-metric and a stopped-flow spectrophotometer. In 3.3×10-3 ~1.2×10-2 mol dm-3 HCl (I=0.5 mol dm-3, HCl + NaCl), the dissociation rate follows the law kobs= kK'[H+]. The acid dissociation can be rationalized in terms of four-step kinetic process involving two rapid pre-equilibrium protonations and rate-determining cleavage of the Zn(II)-N(phenanthroline) bond. Steric effects on the stability of complexes and on the kinetic process have also been discussed