Ismail Abbas

Ampicillin acidity and formation constants with some metals and their thermodynamic parameters in different media. Crystal structures of two polymorphs isolated from the reaction of ampicillin with copper(II)

The dissociation constants of ampicillin and the formation constants of complexes with cobalt(II), copper(II), nickel(II), iron(III), zinc(II), lead(II), mercury(II) and cadmium(II) were evaluated at different temperatures (20–45°C) by potentiometric measurements in the presence of different percentages of ethanol–water. Two polymorphs of the degradation product 3-oxo-2-phenyl-pyrazine-5-carboxylic acid ethyl ester have been isolated from the reaction of copper chloride with ampicillin in aqueous ethanol. In the crystal structure of both polymorphs, molecules related by a center of symmetry form a dimer by coupling of the N–H ··· O hydrogen bonds resulting in the (8) supramolecular synton. The π–π contacts indicate strong stacking interactions in both polymorphs.

Diethyl sulfide modified silica and calix[4]pyrrole chelating resin: Synthesis and mercury(II) cation retention properties

Diethyl sulfide was chemically immobilized on the surface of silica gel (0.2–0.5 and 0.06 mm) for the formation of two newly synthesized silica gel phases (S1 and S2). A new chelating resin containing meso-tetramethyl-tetrakis-(thiophene)calix[4]pyrrole, CP(I), was also synthesized via the condensation of CP(I) with formaldehyde. The selection of this receptor is based on fundamental studies. Among the cations and anions considered, CP(I) interacts only with mercury(II). The functionalized silicas and the calixpyrrole resin were characterized by elemental analysis and mass spectrometry. The batch removal of metal cations (Hg2+, Pb2+ and Cd2+) by these materials from aqueous solutions was investigated. The uptake capacities of the silica based materials (S1 and S2) and calixpyrrole polymers (R1) for the Hg2+ cation were determined. The Hg(II) cation uptake data have been found to fit both, the Langmuir and Freundlich isotherms, and the coefficients indicated favorable uptake of this cation by these materials. Parameters such as the kinetics of the uptake process, pH, temperature, silica particle size and metal-ion concentration effects were evaluated. The data obtained clearly indicate that S1 has the higher uptake capability and faster retention rate for Hg(II) ions relative to S2 and R1. In a column operation, it was observed that the Hg2+ cation was effectively removed from aqueous solution by the calixpyrrole resin, R1. The percentage of recovery of this resin for the Hg2+ cation was found to be higher than 95%. The results obtained are compared with previously reported materials for mercury removal from aqueous solutions.

Development of an in situ Plasma Treatment of X155CrMoV12 for a (Cr,Al)N PVD Tool Coating for Dry Metal Forming in Cold Forging.

A new calix[4]pyrrole-based macrocycle, meso-tetramethyltetrakis-[4-(2-ethoxy)ethoxyphenyl]calix[4]pyrrole, (2) has been prepared and characterized. The binding ability of (2) for metal cations were investigated by ultraviolet–visible spectrophotometry in acetonitrile at 298.15 K. Stability constant and thermodynamic parameters for 1:1 binding interaction between (2) and Pb(II) cation were measured at different temperatures. Ether calix[4]pyrrole polymer, (4) was also synthesized. Solid-phase extraction of Pb(II) cation by (4) from the aqueous media has been studied using the batch method. Various significant extraction parameters (mass, lead concentration, temperature, and time) have been evaluated. Analysis of equilibrium data shows linear fitting with the Langmuir isotherm. Uptake capacity was found to be 80 mg g−1 at 298.15 K. Kinetic studies show a pseudo-second-order reaction mechanism. The thermodynamic parameters of extractions were also calculated.

Chapter 3 Calixpyrrole–Fluoride Interactions: From Fundamental Research to Applications in the Environmental Field

Abstract Synthetic macrocycles such as calixpyrroles are capable of complexing anions and discriminating between them most effectively. This chapter is concerned with calixpyrrole and derivatives with selective properties towards the fluoride anion as demonstrated through the use of spectrometric, electrochemical and thermal (calorimetry) data. Selectivity is one of the main features in supramolecular chemistry. As such the importance of thermodynamics in assessing quantitatively selectivity is emphasised. An account is given about the steps undertaken for the thermodynamic characterisation of the binding process involving calixpyrroles and the fluoride anion in different media. Thus based on stability constant data, selectivity factors are calculated to illustrate the anion, receptor and medium effects on the selective binding of calixpyroles with the fluoride anion. Representative examples are given to demonstrate the role of solvation on the complexation process. The applications of calixpyrroles in the design of sensors and new materials with potential use as decontaminant agents for the removal of fluorides from water are discussed.

Pyridine-substituted calix[4]pyrrole: a new cation receptor

Novel pyridine-substituted calix[4]pyrrole (CP), has been synthesised and characterised by different analytical techniques (1H NMR, microanalysis and mass spectroscopy). The cation-binding behaviour of this receptor was investigated by proton NMR spectroscopy, conductometric and UV titrations. 1H NMR measurements reveal the sites of interaction of the ligand with metal cations in deuterated acetonitrile (CD3CN). The results show that introduction of one pyridine group to the pendent arm of the modified CP enables the produced hybrid to bind with metal cations [Cd(II), Pb(II), Hg(II)] in acetonitrile. No interaction was observed between this ligand and other metal cations in acetonitrile. The composition of the anion complexes was established through conductance measurements. In all cases, 1:1 complexes are formed. The thermodynamics of metal cations complexation in acetonitrile is discussed.