Equilibrium studies of selenite and selenate ions with the receptor complex formed by Cu2+ and 1,4,7,13,16,19-hexaaza-10,22-dioxacyclotetracosane (OBISDIEN)

Synthesis and Solution Structure Analysis of a Bispyrenyl Bishydroxamate Calix[4]arene-Based Receptor, a Fluorescent Chemosensor for Cu2+ and Ni2+ Metal Ions

“…The following materials were used: 1,3-dimethoxy-4- tert -butylcalix[4]arene (Janssen), copper(II) sulfate pentahydrate (Prolabo), nickel(II) sulfate hexahydrate (Merck), and iron(III) nitrate nonahydrate (Aldrich). Potentiometric studies of compound 1 in the absence and in the presence of metal ions were carried out with an Orion model 720A pH meter according to a procedure described elsewhere . Fluorimetric measurements ([ 1 ] = 5 × 10 -7 M, λ exc = 340 nm) were performed at room temperature in methanol/water (80/20 v/v) as solvent using HEPES (10 mM, −log[H + ] = 7.4) as buffer.…”

“…Potentiometric studies of compound 1 in the absence and in the presence of metal ions were carried out with an Orion model 720A pH meter according to a procedure described elsewhere. 40 Fluorimetric measurements ([1] ) 5 × 10 -7 M, λexc ) 340 nm) were performed at room temperature in methanol/water (80/20 v/v) as solvent using HEPES (10 mM, -log[H + ] ) 7.4) as buffer. The ionic strength (µ) was adjusted to 0.1 M (KCl).…”

Equilibrium studies of ternary complexes formed by bromide, sulfate, selenite and selenate ions with Zn2+, Mg2+ and 1, 4, 7, 13, 16, 19-hexaaza- 10, 22- dioxacyclotetracosane (obisdien)

“…All the solutions were titrated with 0.100 M standard CO2 -free KOH. 9,11 . The proton association constants of sulfate, selenite and selenate ions were taken from the literature 31 and the hydrolysis constants of Zn 2+ and Mg 2+ ions were reported by Baes and Mesmer…”

“…Several equilibrium constants of metal complexes were determined and due to the fact that this ligand can be hexaprotonated, the potentiometric titration has been the technique of choice for equilibrium constants determinations 9 . Studies involving the equilibrium determination with anions as Br -, SO4 2-, AsO2 -, PO4 3-, malonic acid, glycine and others 8,10 , and more recently involving SeO3 2-, SeO4 2-, 11 indicates that this ligand is very important for the selective molecular recognition of these anions. Organic anions also bridges binuclear metal complexes 12 .…”