Amer A. G. Al Abdel Hamid

Preferential adsorption of mercury(II) ions in water: chelation of mercury, cadmium, and lead ions to silica derivatized with meso-2,3-dimercaptosuccinic acid

Meso-dimercaptosuccinic acid (DMSA) covalently attached to silica gel via amide bond linkages (DMSA-[silica]) was evaluated as a chelate for Hg(II), Cd(II), and Pb(II). All three metal ions are separately chelated by DMSA-[silica]; 95% of Hg(II) is chelated, 81% of Cd(II), and 74% of Pb(II). When equal molar concentrations of the three metals are allowed to react simultaneously with DMSA-[silica] for 2 h, mercury is preferentially bound (99%) compared to cadmium (13%) or lead (0.4%). Attachment of DMSA to silica surfaces via amide bond formation, which increases the thiol to carboxylic acid ratio over free DMSA, is suggested as a factor in enhancing the preference of DMSA-[silica] for mercury.

Properties of 2-, 3-, and 4-acetylpyridine substituted ruthenium(II) bis(bipyridine) complexes: substituent effect on the electronic structure, spectra, and photochemistry of the complex

Bis(2,2′-bipyridine) complexes of ruthenium(II) with 2-, 3-, and 4-acetylpyridine derivatives were synthesized and structurally characterized. The effect of changing the location of the pyridines acetyl substituent was studied experimentally and theoretically to clarify the effect of substituent position on the chemical behavior and photochemical properties of the complex. The substituent position on the heterocyclic-pyridine was found to strongly affect the chemical and photochemical properties of the complex. Variation of the position of the substituent, and thus ligand modification brought by as a consequence of this variation, offers possibilities to design complexes of desired structural and photochemical properties.

A Selective Chemosensor for Mercuric Ions Based on 4-Aminothiophenol-Ruthenium(II) Bis(bipyridine) Complex

A new ruthenium(II) complex (cis-ruthenium-bis[2,2′-bipyridine]-bis[4-aminothiophenol]-bis[hexafluorophosphate]) has been synthesized and characterized using standard analytical and spectroscopic techniques, FTIR, 1H and 13C-NMR, UV/vis, elemental analysis, conductivity measurements, and potentiometric titration. Investigation of the synthesized complex with metal ions showed that this complex has photochemical properties that are selective and sensitive toward the presence of mercuric ion in aqueous solution. The detection limit for mercuric ions using UV/vis spectroscopy was estimated to be ~ 0.4 ppm. The results presented herein may have an important implication in the development of a spectroscopic selective detection for mercuric ions in aqueous solution.

Chemosensor Engineering : Effects of Halogen Attached to Carbon - Carbon Triple Bond Substituent on Absorption Energy of Pyridine : DFT - Study

Pyridine, C5H5N, and pyridine derivatives of the structure C5(S)nH5-nN (S = -C≡C-X; X = F, Cl, Br, I) have been studied theoretically using DFT computation employing the B3LYP/LanL2DZ level of theory. Effects of substituent halogenation on electron density enrichment of the pyridine nitrogen, and thus its effectiveness as an electron donor have been investigated. Computational results showed that the substituent halogenation does affect the charge density accumulation on the nitrogen atom of pyridine as well as the C2=N and -C≡Cbond lengths and the C2 N C6 bond angle. In addition, charge density localization on the nitrogen atom has been found to depend on the number and position of side substituents. Hardness of the halogen atom attached to the tail of the side substituent has been proved to be a determining factor in promoting and qualifying substituted pyridines to act as effective electron donors. The influence of substituent halogenation on electronic localization or delocalization is further viewed by showing (1) charge density distribution surfaces and (2) occupancy of the HOMO molecular orbitals. The conclusions extracted from this investigation support our previous findings in earlier studies through which we attempt to gain more insights toward putting hands on key factors that are anticipated to qualify chelates to be good stabilizers for metal ion complexes that are demanded as chemosensors. Furthermore, this study is considered an important step of progress in our pursued research work that aims to promote inorganic complexes to act as accessible and low energy absorbers. This is essential when inorganic complexes are needed to be employed as colorimertric detectors in the field of chemosensation.

Comparative study: Correlating extraction efficiency for Hg(II), Cd(II), and Pb(II) metal ions with the chelate stability and total hardness in simple nitrogen donors

ABSTRACT Four N-donors (PHDA, ATPH, APHO, and MTAN) containing NH2 were used to extract Hg(II), Cd(II), and Pb(II). Their extraction capacity was determined by measurement of percentage extraction. The chelates extract these metals differently: for example, efficiency of ATPH was the highest for Hg(II) compared to PHDA, APHO, and MTAN. The extraction efficiency was found to depend on: donor atom hardness, chelate total hardness, metal: chelate mole ratio and substituent’s electronic effects. Among all, total hardness and chelate stability are key factors and molecule of small (EHOMO – ELUMO) is more reactive, where extraction efficiency increases as molecular stability decreases.ABSTRACTFour N-donors (PHDA, ATPH, APHO, and MTAN) containing NH2 were used to extract Hg(II), Cd(II), and Pb(II). Their extraction capacity was determined by measurement of percentage extraction.The chelates extract these metals differently: for example, efficiency of ATPH was the highest for Hg(II) compared to PHDA, APHO, and MTAN.The extraction efficiency was found to depend on: donor atom hardness, chelate total hardness, metal: chelate mole ratio and substituent’s electronic effects. Among all, total hardness and chelate stability are key factors and molecule of small (EHOMO – ELUMO) is more reactive, where extraction efficiency increases as molecular stability decreases.

Bis-Chelated Pd(II)-Amino Acid Complexes: Substitution Reactions of cis-Dichlorobis(benzonitrile)Palladium(II) with Amino Acids

The substitution reactions of the benzonitrile (PhCN) complex cis-[Pd(PhCN)2C12] with the sodium salts of some amino acids, namely L-tyrosine (tyrH), L-phenylalanine (pheH), L-glutamic acid (gluH), L-glutamine (glnH), L-cysteine (cysH), and glycine (glyH) have been investigated. The isolated complexes [Pd(tyr)2].0.5H2O, [Pd(phe)2].H2O, [Pd(glu)2], [Pd(gln)2].H2O, Na2[Pd(cys)2].0.5Me2CO, and [Pd(gly)2].0.5H2O have been characterized by elemental analysis, conductivity measurements, IR, electronic absorption, and 1H- and 13C-NMR spectra. Based on these data, all amino acid anions are found to behave as bidentates through the ‒NH2 and ‒COO− groups except the cysteinate ion which bonds to Pd(II) through ‒NH2 and ‒S− groups.

Influence of AgYzeolite on the photocatalyticoxidation of pirimicarb

Silver clusters were incorporated into the Y zeolite framework and used as a photocatalyst toward pirimicarb. X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), and low-temperature steady-state photoluminescence spectroscopic data indicate the formation of metallic silver as well as ionic clusters. The photodecomposition of the pirimicarb pesticide is enhanced in the presence of silver doped into zeolite Y; where the observed rate constant in the presence of the catalyst is 2.2 × 10 –2 min –1 compared to the rate constant of 7.0 × 10 –4 min –1 for the uncatalysed irradiated pirimicarb solution. GC-MS indicates that while pirimicarb alone was hydrolysed into N-N-dimethylcarbamic acid and 2-dimethylamino-5,6-dimethylpyrimidin-4-ol; the presence of AgY catalyst produced the selective oxidation product 4-dimethylcarbamoyloxy-5,6-dimethylpyrimidin-2-yl-carbimic acid.

Comparative study: Correlating extraction efficiency of simple diacid chelates for Hg(II), Cd(II), and pb(II) ions with the number of (CH2) units connecting COO− groups

ABSTRACTFour dicarboxylic chelates (MAL, SUC, ADP, and SUP) were employed to explore the effect of (CH2) extension on extraction efficiency of the corresponding dicarboxylates for Hg(II), Cd(II), and pb(II) ions. Binding effectiveness (extraction efficiency) for the forementioned ions was determined by measuring the percent of extraction.The efficiency of extraction was found to depend on number of (CH2) units within the chelate. This result was deduced after correlating the extraction efficiency with the number of (CH2) units in the diacid chelate. Parameters like charge density distribution and HOMO energy were found to support the proceeded conclusion.ABSTRACT Four dicarboxylic chelates (MAL, SUC, ADP, and SUP) were employed to explore the effect of (CH2) extension on extraction efficiency of the corresponding dicarboxylates for Hg(II), Cd(II), and pb(II) ions. Binding effectiveness (extraction efficiency) for the forementioned ions was determined by measuring the percent of extraction. The efficiency of extraction was found to depend on number of (CH2) units within the chelate. This result was deduced after correlating the extraction efficiency with the number of (CH2) units in the diacid chelate. Parameters like charge density distribution and HOMO energy were found to support the proceeded conclusion.