New potentiometric experiments have been performed in NaCl and in (CH3)4NCl media, to determine the protonation constants, the protonation enthalpy changes and the solubility of six natural α-amino acids, namely Glycine (Gly), Alanine (Ala), Valine (Val), Leucine (Leu), Serine (Ser) and Phenylalanine (Phe). The aim of the work is the rationalization of the protonation thermodynamics (log [Formu...

The sorption kinetics of the divalent metals Zn, Co, Ni, and Cd to hematite were studied in single sorbate systems with high sorbate/sorbent ratios (from 1.67 to 3.33mol sorbate/mol sorption sites) in 10mM Na-piperazine N,N'-bis 2-ethane sulfonic acid (Na-PIPES) solution at pH 6.8. The experimental data showed a rapid initial sorption (half-time about 1min) followed by slower sorption that cont...

The complexation reactions between methylthymol blue (MTB) and Co2+, Ni2+, Cu2+, Zn2+ and Pb2+ ions have been studied in different water-methanol mixtures at pH 4.45 and 25 °C by a spectrophotometric technique. The stepwise stability constants of the resulting 1:1 and 2:1 (metal ion to ligand) complexes were determined from the absorban...

Three new Schiff bases derived from the condensation reaction of thiophene-2-carbaldehyde and DL-alanine, DL-valine and DL-phenylalanine have been synthesized and their Co(II), Ni(II) and Cu(II) complexes have been prepared. The Schiff bases and the complexes have been characterized by their analytical and spectral data. The protonation constants of the Schiff bases and stability constants of t...

The synthesis and isolation of the sodium salt of cyclo-tri-μ-imidotetraphosphate, i.e. Na4cP4O9(NH)3·H2O, were achieved by the hydrolysis of Na4cP4O8(NH)4·2H2O under very weak acidic conditions, i.e. using 0.2 mol L(-1) propionic acid and the pH-controlled recrystallization procedure. The purity of Na4cP4O9(NH)3·H2O was improved from 2% to 95% by the pH-controlled recrystallization only two ti...

Some new compounds based on bis-benzimidazole moieties have been synthesized and characterized by IR and NMR spectroscopies. The ability of 3a in transition metal cation sensing such as Co2+, Ni2+, Zn2+, Mn2+, Fe2+ and Cu2+ have been investigated by Uv-vis and fluorescence spectroscopy in methanol solvent. The complexation constants and complex stoichiometry of Cu2+ have been determined. The ex...

The binding constants of acetate and benzoate to a Pheha-based 15-metallacrown-5 have been determined by a fluorimetric indicator displacement assay demonstrating on a thermodynamic basis the stabilization effect arising from complexation of the less polar carboxylate into the hydrophobic pocket of the metallacrown scaffold.

The complexation reactions between N,N'-3,6-dioxa-1,8-octanebis (salicylaldimine) [saldioxen(I)] and Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) were studied spectrophotometrically in methanol solution at 25 °C. The stoichiometry of the complexes were obtained as 2:1 and 1:1 sadioxen-metal ion using mole ratio method. The formation constants of the complexes were determined, a...

Oleuropein (OLE) is a major constituent of the olive leaf and green olives (Olea europaea). It has antioxidant and therapeutic properties and is valued as a medicinal component. The molecule is a complex phenolic compound constituted by a heterosidic ester of the elenolic acid and dihydroxy ethanol. This work concerns the determination of the inclusion complex constants between OLE and cyclodex...

Proton and Cu(II), Zn(II), Cd(II) and Pb(II) binding by ligand H(2)L, containing two bis(aminoethyl)amine (dien) units connected by a 2',7'-dichlorofluorescein (DCF) unit has been analyzed by means of potentiometric, UV-vis and fluorescence emission measurements. Considering proton binding, the ligand in its fully deprotonated form, L(2-), binds up to four acidic protons in the alkaline pH regi...