Chelating Ligands

Developing more efficient catalysts remains one of the primary targets of organometallic chemists. To accelerate reaching this goal, effective molecular descriptors and visualization tools can represent a remarkable aid. Here, we present a Web application for analyzing the catalytic pocket of metal complexes using topographic steric maps as a general and unbiased descriptor that is suitable for every class of catalysts. To show the broad applicability of our approach, we first compared the steric map of a series of transition metal complexes presenting popular mono-, di-, and tetracoordinated ligands and three classic zirconocenes. This comparative analysis highlighted similarities and differences between totally unrelated ligands. Then, we focused on a recently developed Fe(II) catalyst that is active in the asymmetric transfer hydrogenation of ketones and imines. Finally, we expand the scope of these tools to rationalize the inversion of enantioselectivity in enzymatic catalysis, achieved by point mutation of three amino acids of mononuclear p-hydroxymandelate synthase.

The new cyclohexane-fused CyAAZTA ligand was synthesized to increase the structural rigidity of the heptadentate chelator AAZTA with the aim of improving the overall stability of its Ga III complex. The stability constant of Ga(CyAAZTA) À , determined both by pH-potentiometry (logK GaL = 21.39) and by 71 Ga NMR (logK GaL = 21.92), was found similar to that of GaAAZTA (logK GaL = 22.18). The kinetic inertness of Ga(CyAAZTA) À was investigated by following its transmetallation and ligand exchange reactions with Cu 2 + and human serum transferrin, respectively. The formation of a hydroxido-complex near pH 7 decreases the half-life (t 1/2 ) of the dissociation reactions for Ga (CyAAZTA) À compared to Ga(AAZTA) À (8.5 h vs 21 h, pH 7.4). However, at pH < 7 the t 1/2 of Ga(CyAAZTA) À is much longer (234 h at pH 6). Finally, CyAAZTA was successfully radiolabelled with 68 Ga in acetate buffer at pH 3.8, in 15 minutes at room temperature at [CyAAZTA] = 10 mM, with a labelling yield higher than 80 %. A 1 mM solution of CyAAZTA was successfully labelled (L.Y.: 97.4 %) in 5 minutes at 90 8C. Stability tests in human serum and in the presence of 50 mM DTPA showed no significant decomposition of 68 GaCyAAZTA over 90 minutes.

A series of organometallic complexes of the form [(PhH)Ru-(amino acid)] + have been synthesized using amino acids able to act as tridentate ligands. The straightforward syntheses gave enantiomerically pure complexes with two stereogenic centers due to the enantiopurity of the chelating ligands. Complexes were characterized in the solid-state and/or solution-state where the stability of the complex allowed. The propensity toward labilization of the coordinatively saturated complexes was investigated. The links between complex stability and structural features are very subtle. Nonetheless, H/D exchange rates of coordinated amino groups reveal more significant differences in reactivity linked to metallocycle ring size resulting in decreasing stability of the metallocycle as the amino acid side-chain length increases. The behavior of these systems in acid is unusual, apparently labilizing the carboxylate residue of the amino acid. This acid-catalyzed hemilability in an organometallic is relevant to the use of Ru(II) arenes in medicinal contexts due to the relatively low pH of cancerous cells.

Porous solid siloxane polymers carrying diamine functional group of formula P-(CH 2) 3 NH-CH 2 CH 2 NH 2 (where P-represents a silica-like siloxane framework) have been prepared by replacement of the iodine in iodopolysiloxane with ethylenediamine. The iodofunctionalized polysiloxane was prepared by polycondensation of Si(OEt) 4 and (MeO) 3 Si(CH 2)I. The polysiloxane diamine ligand system exhibits high potential for preconcentration of divalent metal ions (Cu 2+ , Zn 2+ , and Cd 2+). The tendency to chemisorb these divalent metal ions by the diamine ligand system at the optimum conditions was found in the order: Cu 2+ > Zn 2+ > Cd 2+. Diamine ligand system suffers from leaching of ligand containing groups upon treatment with acidic solutions.

Despite the rich coordination chemistry, hydroxylamines are rarely used as
ligands for transition metal coordination compounds. This is partially because of the instability of these complexes that undergo decomposition, disproportionation and oxidation processes involving the hydroxylamine motif. Here, we design macrocyclic poly-N-hydroxylamines (crown-hydroxylamines) that form complexes containing a d-metal ion (Cu(II), Ni(II), Mn(II), and Zn(II)) coordinated by multiple (up to six) hydroxylamine fragments. The stability of these complexes is likely to be due to a macrocycle effect and strong intramolecular H-bonding interactions between the N−OH groups. Crown-hydroxylamine complexes exhibit interesting pH-dependent behavior where the efficiency of metal binding increases upon deprotonation of the hydroxylamine groups. Copper complexes exhibit catalytic activity in aerobic oxidation reactions under ambient conditions, whereas the corresponding complexes with macrocyclic polyamines show poor or no activity. Our results
show that crown-hydroxylamines display anomalous structural features and chemical behavior with respect to both organic hydroxylamines and polyaza-crowns.

Keratinocyte (KC) apoptosis plays a critical role in regulating epidermal development and restraining carcinogenesis. Apoptosis balances proliferation to maintain epidermal thickness, contributes to stratum corneum formation and may eliminate pre-malignant cells. Apart from the normal developmental program, KC apoptosis can be triggered by UV light and other stimuli. Dysfunctional apoptosis occurs in some skin diseases, such as psoriasis and skin cancer. Here we review the current state of knowledge of KC apoptosis, with particular focus on apoptotic signaling pathways and molecular mechanisms of apoptosis control, and discuss new insights into the complex role of apoptosis in skin carcinogenesis that are emerging from mouse models.

The organometallic complexes of general formulae [Me2Ga{η2‐E,E′‐[R2P(E)NP(E′)R′2]}] [R = R′ = Ph, E = E′ = O (1); R = R′ = Ph, E = E′ = S (2); R = R′ = Ph, E = E′ = Se (3); R = R′ = Ph, E = O, E′ = S (4); R = Me, R′ = Ph, E = S, E′ = O (5)] and [Me2Ga{η2‐S,S′‐[Ph2P(S)NC(S)(C9H10N)]}] (6) were obtained by facile methane elimination reactions from GaMe3 and the acidic ligands L1H [(XPPh2)2NH (X = O, S, Se), (OPPh2)(SPPh2)NH, and (OPMe2)(SPPh2)NH] and L2H [Ph2P(S)NHC(S)(C9H10N)] in toluene. Replacement of one phosphorus atom by a carbon atom in the ligand skeleton of L1H gave the new ligand L2H, which, upon reaction with GaMe3, gave compound 6, which shows no significant structural differences with respect to 1−5. Therefore, L2H does not induce partial planarity in the six‐membered ring, indicating the necessity for replacing both phosphorus atoms of the ligand by carbon atoms, as in the β‐diketonate‐type derivatives, in order to impose ring planarity. Thus, despite originating from a ...

This study was conducted to investigate the effect of external iron status and arsenic species on chelant-enhanced iron bioavailability and arsenic uptake. Rice seedlings (Oryza sativa L.) were used as model plant, and were grown in artificially contaminated sandy soils irrigated with Murashige and Skoog (MS) culture solution. Arsenate uptake in roots shoots of rice seedlings were affected significantly (p > 0.05) while dimethylarsinic acid (DMAA) was not by the additional iron and chelating ligand treatments. Regardless of iron concentrations in the soil solution, HIDS increased arsenic uptake for roots more than EDTA and EDDS. Chelating ligands and arsenic species also influenced iron uptake in rice roots. Irrespective of arsenic species, HIDS was found to be more effective in the increase of iron bioavailability and uptake in rice roots compared to other chelants. There was a significant positive correlation (r = 0.78, p < 0.05) between arsenate and iron concentrations in the roots of rice seedlings grown with or without additional iron indicating that arsenate inhibit iron uptake. In contrast, there was no correlation between iron and DMAA uptake in roots. Poor correlation between iron and arsenic in shoots indicated that iron uptake in shoots was neither affected by additional iron nor by arsenic species. Compared to the control, chelating ligands increased iron uptake in shoots of rice seedlings significantly (p < 0.05). Regardless of additional iron and arsenic species, iron uptake in rice shoots did not differed among EDTA, EDDS, and HIDS treatments.

A new route for the synthesis of immobilized-polysiloxane ligand system bearing iminodiacetic acid chelating ligand of the general formula P-(CH 2) 3 N-(CH 2 COOEt) 2 , (where P represents [Si-O] n polysiloxane network) was accomplished. The preparation of the immobilized iminodiethylacetate was achieved by the reaction of 3-aminopropyltrimethoxysilane with ethyl chloroacetate followed by hydrolytic polycondensation of the diethyliminodiacetate silane agent and tetraethylorthosilicate via the sol-gel process. The immobilized iminodiacetic acid P-(CH 2) 3 N-(CH 2 COOH) 2 was obtained by hydrolysis of the ethyl acetate groups using diluted hydrochloric acid. The new functionalized ligand system exhibits high capacities for uptake of the metal ions (Co 2+ , Ni 2+ , Cu 2+ and Zn 2+), and forms 1:1 metal to ligand ratio complexes in the case of Ni 2+ and Cu 2+ .

Porous solid insoluble polysiloxane-immobilized ligand system bearing propylamine of the general formula P-(CH 2) 3-NH 2 (where P represents [Si O] n siloxane network) was prepared and evaluated for the separation and preconcentration of copper(II) from aqueous solution. The ligand system retained Cu(II) effectively when used as a metal ion extractant. The ligand system also showed high selectivity to separate copper(II) from a mixture of metal ions (Co(II), Ni(II), Cu(II)) when used as chromatographic stationary phase. The optimum pH appeared to be pH = 5.5 using acetate buffer as an eluent. Thermal analysis showed that the ligand system is very stable at relatively high temperatures.

A new route for the synthesis of immobilized-polysiloxane ligand system bearing iminodiacetic acid chelating ligand of the general formula P-(CH 2) 3 N-(CH 2 COOEt) 2 , (where P represents [Si-O] n polysiloxane network) was accomplished. The preparation of the immobilized iminodiethylacetate was achieved by the reaction of 3-aminopropyltrimethoxysilane with ethyl chloroacetate followed by hydrolytic polycondensation of the diethyliminodiacetate silane agent and tetraethylorthosilicate via the sol-gel process. The immobilized iminodiacetic acid P-(CH 2) 3 N-(CH 2 COOH) 2 was obtained by hydrolysis of the ethyl acetate groups using diluted hydrochloric acid. The new functionalized ligand system exhibits high capacities for uptake of the metal ions (Co 2+ , Ni 2+ , Cu 2+ and Zn 2+), and forms 1:1 metal to ligand ratio complexes in the case of Ni 2+ and Cu 2+ .

Complexation and thermodynamic studies of insoluble porous solid polysiloxane immobilized ligand systembearing chelating ligand group of the general formula P-(CH2)3-N[CH2CONH(CH2)2NH(CH2)2NH2]2, (Where P represents [Si-O]n polysiloxane network) were studied. TheBatch equilibration method has been performed to calculate the distribution coefficient (KD) and the thermodynamic parameters (G , H , and TS) for the stoichiometric 1:1 complexation of Co2+, Ni2+, and Cu2+ ions with iminobis(diethylenediamineacetamide) polysiloxane. The complexation behavior at pH 5 in aqueous media is discussed from the thermodynamic point of view.

A porous solid polysiloxane ligand system of the general formula P-(CH 2) 3-NH-CH 2 COONHCH 2 CH 2 NH 2 , (where P represents [Si-O] n siloxane network) has been prepared by modification of the immobilized 3aminopropylpolysiloxane, P-(CH 2) 3 NH 2 , with ethyl chloroacetate followed by ethylenediamine. The new modified polysiloxane system exhibits good potential for uptake of metal ions (Co 2+ , Cu 2+ , Zn 2+ and Pb 2+). This ligand system gives more stable complexes with metal ions than its parent 3aminopropylpolysiloxane precursor. Thermogravimetric analyses of this ligand system and its copper complex show high stability at relatively high temperature.

An extraction chromatographic solid porous polysiloxane functionalized by chelating diethylenetriamine ligand of the general formula P-(CH2)3-NH(CH2)2NH(CH2)2NH2, (Where P represents [Si-O]nsiloxane network) has been evaluated for the separation of Co(II), Ni(II) and Cu(II) from aqueous solutions. The chromatographic parameters of the separation method have been optimized. The ligand system retained Co(II), Cu(II) and Zn(II) effectively when used as a metal ion extractant by controlling the pH value. The ligand system also shows a good separation of a mixture of metal ions Co(II), Ni(II) and Cu(II) when used as chromatographic stationary phase. The optimum separation pH values were 4.5, 4 for Co(II) and Ni(II) respectively, while a solution of 0.1 M HNO3was used to elute Cu(II). Metal ions were also preconcentrated at pH 5.5. The chemisorbed metal ions were regenerated from the solid extractant using 0.5 M HCl.

A porous solid polysiloxane ligand system of the general formula P-(CH 2) 3-C 7 H 6 NO, (where P represents [Si-O] n siloxane network) has been prepared by modification of the immobilized 3-aminopropylpolysiloxane, P-(CH 2) 3 NH 2 with an exsess of salicylaldehyde. The new modified polysiloxane system exhibits good potential for uptake of Co 2+ and Cu 2+ metal ions. This ligand system gives more stable complexes with the divalent metal ions than its parent 3-aminopropylpolysiloxane precursor. Characterization was achieved using elemental analysis and FTIR spectroscopy.

Porous solid bi-organofunctionalized diamine-thiol polysiloxane immobilized ligand system of the general formula P-(CH 2) 3-X, (where P represents [Si-O] n siloxane network and X represents a mixture of diamine;-NH(CH) 2 NH 2 and thiol;-SH functional groups) has been prepared by hydrolytic polycondensation of TEOS with a mixture of 3-mercaptopropyltrimethoxysilane and 3-(2-aminoethylimino)propyltrimethoxysilane agents. The ligand system was evaluated for extraction and preconcentartion of a series of divalent metal ions from aqueous solutions including: Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ and Pb 2+. Both batch and dynamic methods were used to examine maximum sorption capacity. The maximum binding capacity followed the sequence; Cu 2+ > Pb 2+ > Cd 2+ > Ni 2+ > Zn 2+ > Co 2+ at pH 5.5. Measurement of variation of sorption of metal ions with temperature yielded negative values of ΔG° and positive values of ΔS° and ΔH° indicating a spontaneous and endothermic process of binding metal ions to the ligand system.

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Immobilized-polysiloxane (diamine-thiol) tetraethylacetate, P-(NN-S)-TEA (where P represents [Si-O] n polysiloxane network), was synthesized using one-pot reaction of tetraethylorthosilicate (TEOS) with 3-(ethylenediaminetriethylacetate) propyltrimethoxysilane and 3-thiolethylacetatepropyltrimethoxysilane in the presence of cetyl trimethylammonium bromide (CTAB) as a surfactant. Its ethylenediamine and diethylenetriamine modified polysiloxane (diamine-thiol)-tetrakis(N-2-aminoethylacetamide), P-(NN-S)-TEA-NN, and polysiloxane (diamine-thiol)-tetrakis(N-diethylenediamineacetamide), P-(NN-S)-TEA-NNN chelating ligand systems were also obtained. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopic (XPS), and thermogravimetric analysis (TGA) techniques have been used for establishing their structures. An elemental CHNX combustion analyzer was used to determine the mass fractions of carbon, hydrogen, nitrogen, and sulfur of samples. The metal uptake capacities results showed that the modified polysiloxane ligand systems exhibited high capacities for the uptake of divalent metal ions in the following order: Cu 2+ > Pb 2+ > Ni 2+ > Co 2+ .

Template Synthesis of Iminodiacetic Acid Polysiloxane Immobilized Ligand System and Their Metal Uptake Capacity Two different routes for the synthesis of insoluble porous solid functionalized ligand system bearing iminodiacetic acid chelating ligand of the general formula P-(CH 2) 3 N-(CH 2 COOH) 2 (where P-represents [Si-O]n polysiloxane network) were achieved by sol-gel template method in presence of CTAB surfactant to formed porous materials. The first route was achieved by the modification of 3-aminopropylpolysiloxane with ethylchloroacetate, followed by hydrolysis with HCl to form the polysiloxane iminodiacetic acid ligand system; P-(CH 2) 3 N-(CH 2 COOH) 2 (P-IDA-I). The second route was achieved by the reaction of diethyliminodiacetate with 3-iodopropylpolysiloxane to form immobilizedpolysiloxane diethyliminodiacetate system. The diethyliminodiacetate polysiloxane immobilized ligand system was then hydrolyzed by HCl to form the iminodiacetic acid ligand system P-(CH 2) 3 N-(CH 2 COOH) 2 (P-IDA-II). Elemental analysis, 13 C NMR, XPS and FTIR results showed that the surfactant have improved the silica network structure and increased the metal uptake capacity of the ligand system. Thermogravimetric analysis studies showed significant stability of the immobilized ligand systems upon complexation with metal ions. The new functionalized ligand systems exhibit high capacities for uptake of the metal ions (Ni 2+ , Cu 2+ and Pb 2+).

Insoluble porous solid polysiloxane immobilized ligand system bearing chelating ligand group of the general formula P-(CH 2) 3 N-[CH 2 CONH(CH 2) 2 NH(CH 2) 2 NH 2 ] 2 (where P represents [Si-O] n polysiloxane network) has been prepared by the reaction between the polysiloxane immobilized diethyliminodiacetate ligand system, P-(CH 2) 3 N(CH 2 CO 2 Et) 2 and diethylenetriamine in toluene. The XPS and FTIR results showed that all ethylacetate groups (-COOEt) are converted into the amide groups (-N-C=O). The new functionalized ligand system exhibits high capacity for the uptake of the metal ions (Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+). Complexation of the prepared ligand system for these metal ions at the optimum conditions was found in the order: Cu 2+ > Ni 2+ > Fe 3+ > Co 2+ > Mn 2+ > Zn 2+. This ligand system shows higher capacity toward the metal ions than its iminiodiactate precursor which we have been reported. Stability studies of the immobilized ligand system show high degradation of the siloxane network and leaching of some species upon treatment with strong acidic or basic aqueous solutions in addition to metal ion solutions. Minimum leaching was observed at pH 6-8.

Insoluble solid porous ethyl-2-iminobenzoate immobilized polysiloxane ligand system of the general formula P-(CH 2) 3-NH(C 6 H 4)COOC 2 H 5 , (where P represents [Si-O] n siloxane network) has been prepared by the reaction of 3-iodopolysiloxane P-(CH 2) 3-I with ethyl-2-aminobenzoate. The modified polysiloxane derivatives; imino(N-2-aminoethyl)benzamide P-(CH 2) 3-NH(C 6 H 4)CONH(CH 2) 2 NH 2 , and imino(N-diethylenediamine)benzamide P-(CH 2) 3-NH(C 6 H 4)CONH(CH 2) 2 NH(CH 2) 2 NH 2 ligand systems were prepared by the reaction of ethyl-2-iminobenzoate ligand system with ethylenediamine and diethylenetriamine, respectively. The new modified polysiloxane ligand systems exhibit high potential for the uptake of the metal ions (Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+) with an efficiency of 92-98% after recovery from its primary metal complexes. These immobilized-polysiloxane ligand systems undergo chemical degradation the level of which depends on pH.

A new insoluble solid functionalized ligand system bearing chelating ligand group of the general formula P-(CH 2) 3-N[CH 2 CONH(C 6 H 4)NH 2 ] 2 , where P represents [Si-O] n polysiloxane network, was prepared by the reaction of the immobilized diethyliminodiacetate polysiloxane ligand system, P-(CH 2) 3 N(CH 2 CO 2 Et) 2 with 1,2-diaminobenzene in toluene. 13 C CP-MAS NMR, XPS and FTIR results showed that most ethylacetate groups (-COOEt) were converted into the amide groups (-N-C=O). The new functionalized ligand system exhibits high capacity for extraction and removal of the metal ions (Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+) with efficiency of 95-97% after recovery from its primary metal complexes. This functionalized ligand system formed 1:1 metal to ligand complexes.

The immobilized silica gel ligand systems made by modification of silica surfaces have been briefly summarized. Short background was described based on the synthesis methods and their applications. In this review more attention towards the functionalized polysiloxane xerogels and their postmodification has been given. Polysiloxane-immobilized ligand systems bearing organofunctionalized ligand groups of general formula P-(CH 2) 3-X (where P represents a three-dimensional silica like network-matrix and X is an organofunctional group) were prepared through the sol-gel process by hydrolytic polycondensation of Si(OR) 4 and the appropriate silane coupling agent (RO) 3 Si(CH 2) 3 X (where R is an alkyl group, e.g CH 3 or C 2 H 5). There are many other immobilized ligand systems, which were prepared by treatment of post-polysiloxane precursors with an appropriate organofunctional ligand. Variety of functionalized materials ranging from simple up to macrocyclic immobilized ligand systems were prepared and well characterized. These materials have the advantage over the functionalized silica, as they can be prepared using different molar ratios of Si(OR) 4 and (RO) 3 Si(CH 2) 3 X silane agents, and therefore their metal uptake capacities can be altered. A mixture of two different ligand groups can also be achieved on the same matrix. Analytical and environmental applications of these materials have been reported including extraction, separation and preconcentration of metal ions. A variety of physical chemistry techniques that were employed to characterize the surface and the bulk of the immobilized systems were reported. These included high-resolution solid-state nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR).

Rice husk ash (RHA) was used to prepare sodium silicate, which in turn was functionalized with 3-(chloropropyl)triethoxysilane employing the sol-gel technique to form RHACCl. Chloro group in RHACCl was replaced with iodo group forming RHACI. Ethylenediamine was immobilized on RHACI in order to prepare it for the reaction with salicylaldehyde to form a silica derivative-salen. FT-IR analysis indicated the presence of secondary amine and –NH and C=N absorption bands. XRD analysis revealed the occurrence of the broad diffused peak with maximum intensity at 22–23° (2θ). BET measurements showed also that the surface area of the prepared compound is 274.55 m2/g. Elemental analysis proved the existence of nitrogen in the structure of the prepared compound. The silica derivative-salen showed high potential for extraction and removal of heavy contaminating metal ions Ni(II), Cu(II), and Co(II) from aqueous solutions. The kinetic study demonstrates that the adsorption of the metal ions follow...

Background: Effective wastewater treatments are paramount to modern-day Scientists. The available methods are ineffective in detoxifying tannery wastewater. Aim: This study synthesize and characterized polysiloxane-Immobilized thiosalicylic-mercaptoethanol ligand system (PITSMCBLS) and used in detoxification of Cr3+ and Fe3+ from tannery wastewater.Method: Porous solid PITSMCBLS was prepared by hydrolytic polycondensation of tetraethylorthosilicate with mixture of 3-chloropropyltrimethoxysilane, methanol and sodium hydroxide as catalyst. The gelation formed (3-CPP) after 40 min, was functionalized (F-3CPP) with excess ethylchloroacetate, triethylamine and grafted with thiosalicylic-mercaptoethanol bi-ligand. The PITSMCBLS was characterized using FTIR and SEM-EDX. The competitive sorption characteristics of metal ions (Cr3+ and Fe3+) were studied using Microwave Plasma Atomic-Emission Spectrophotometer.Result: The FTIR spectrum of PITSMCBLS showed vibrational frequencies (cm-1) at: 3...

Insoluble porous solid polysiloxane immobilized ligand system bearing chelating ligand group of the general formula P-(CH 2) 3 N-[CH 2 CONH(CH 2) 2 NH(CH 2) 2 NH 2 ] 2 (where P represents [Si-O] n polysiloxane network) has been prepared by the reaction between the polysiloxane immobilized diethyliminodiacetate ligand system, P-(CH 2) 3 N(CH 2 CO 2 Et) 2 and diethylenetriamine in toluene. The XPS and FTIR results showed that all ethylacetate groups (-COOEt) are converted into the amide groups (-N-C=O). The new functionalized ligand system exhibits high capacity for the uptake of the metal ions (Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+). Complexation of the prepared ligand system for these metal ions at the optimum conditions was found in the order: Cu 2+ > Ni 2+ > Fe 3+ > Co 2+ > Mn 2+ > Zn 2+. This ligand system shows higher capacity toward the metal ions than its iminiodiactate precursor which we have been reported. Stability studies of the immobilized ligand system show high degradation of the siloxane network and leaching of some species upon treatment with strong acidic or basic aqueous solutions in addition to metal ion solutions. Minimum leaching was observed at pH 6-8.

Insoluble solid porous ethyl-2-iminobenzoate immobilized polysiloxane ligand system of the general formula P-(CH 2) 3-NH(C 6 H 4)COOC 2 H 5 , (where P represents [Si-O] n siloxane network) has been prepared by the reaction of 3-iodopolysiloxane P-(CH 2) 3-I with ethyl-2-aminobenzoate. The modified polysiloxane derivatives; imino(N-2-aminoethyl)benzamide P-(CH 2) 3-NH(C 6 H 4)CONH(CH 2) 2 NH 2 , and imino(N-diethylenediamine)benzamide P-(CH 2) 3-NH(C 6 H 4)CONH(CH 2) 2 NH(CH 2) 2 NH 2 ligand systems were prepared by the reaction of ethyl-2-iminobenzoate ligand system with ethylenediamine and diethylenetriamine, respectively. The new modified polysiloxane ligand systems exhibit high potential for the uptake of the metal ions (Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+) with an efficiency of 92-98% after recovery from its primary metal complexes. These immobilized-polysiloxane ligand systems undergo chemical degradation the level of which depends on pH.

A new route for the synthesis of immobilized-polysiloxane ligand system bearing iminodiacetic acid chelating ligand of the general formula P-(CH 2) 3 N-(CH 2 COOEt) 2 , (where P represents [Si-O] n polysiloxane network) was accomplished. The preparation of the immobilized iminodiethylacetate was achieved by the reaction of 3-aminopropyltrimethoxysilane with ethyl chloroacetate followed by hydrolytic polycondensation of the diethyliminodiacetate silane agent and tetraethylorthosilicate via the sol-gel process. The immobilized iminodiacetic acid P-(CH 2) 3 N-(CH 2 COOH) 2 was obtained by hydrolysis of the ethyl acetate groups using diluted hydrochloric acid. The new functionalized ligand system exhibits high capacities for uptake of the metal ions (Co 2+ , Ni 2+ , Cu 2+ and Zn 2+), and forms 1:1 metal to ligand ratio complexes in the case of Ni 2+ and Cu 2+ .

A new route for the synthesis of immobilized-polysiloxane ligand system bearing iminodiacetic acid chelating ligand of the general formula P-(CH 2) 3 N-(CH 2 COOEt) 2 , (where P represents [Si-O] n polysiloxane network) was accomplished. The preparation of the immobilized iminodiethylacetate was achieved by the reaction of 3-aminopropyltrimethoxysilane with ethyl chloroacetate followed by hydrolytic polycondensation of the diethyliminodiacetate silane agent and tetraethylorthosilicate via the sol-gel process. The immobilized iminodiacetic acid P-(CH 2) 3 N-(CH 2 COOH) 2 was obtained by hydrolysis of the ethyl acetate groups using diluted hydrochloric acid. The new functionalized ligand system exhibits high capacities for uptake of the metal ions (Co 2+ , Ni 2+ , Cu 2+ and Zn 2+), and forms 1:1 metal to ligand ratio complexes in the case of Ni 2+ and Cu 2+ .

Porous solid insoluble polysiloxane-immobilized ligand system bearing propylamine of the general formula P-(CH 2) 3-NH 2 (where P represents [Si O] n siloxane network) was prepared and evaluated for the separation and preconcentration of copper(II) from aqueous solution. The ligand system retained Cu(II) effectively when used as a metal ion extractant. The ligand system also showed high selectivity to separate copper(II) from a mixture of metal ions (Co(II), Ni(II), Cu(II)) when used as chromatographic stationary phase. The optimum pH appeared to be pH = 5.5 using acetate buffer as an eluent. Thermal analysis showed that the ligand system is very stable at relatively high temperatures.

The immobilized silica gel ligand systems made by modification of silica surfaces have been briefly summarized. Short background was described based on the synthesis methods and their applications. In this review more attention towards the functionalized polysiloxane xerogels and their postmodification has been given. Polysiloxane-immobilized ligand systems bearing organofunctionalized ligand groups of general formula P-(CH 2) 3-X (where P represents a three-dimensional silica like network-matrix and X is an organofunctional group) were prepared through the sol-gel process by hydrolytic polycondensation of Si(OR) 4 and the appropriate silane coupling agent (RO) 3 Si(CH 2) 3 X (where R is an alkyl group, e.g CH 3 or C 2 H 5). There are many other immobilized ligand systems, which were prepared by treatment of post-polysiloxane precursors with an appropriate organofunctional ligand. Variety of functionalized materials ranging from simple up to macrocyclic immobilized ligand systems were prepared and well characterized. These materials have the advantage over the functionalized silica, as they can be prepared using different molar ratios of Si(OR) 4 and (RO) 3 Si(CH 2) 3 X silane agents, and therefore their metal uptake capacities can be altered. A mixture of two different ligand groups can also be achieved on the same matrix. Analytical and environmental applications of these materials have been reported including extraction, separation and preconcentration of metal ions. A variety of physical chemistry techniques that were employed to characterize the surface and the bulk of the immobilized systems were reported. These included high-resolution solid-state nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR).

Porous solid insoluble polysiloxane-immobilized ligand system bearing propylamine of the general formula P-(CH 2) 3-NH 2 (where P represents [Si O] n siloxane network) was prepared and evaluated for the separation and preconcentration of copper(II) from aqueous solution. The ligand system retained Cu(II) effectively when used as a metal ion extractant. The ligand system also showed high selectivity to separate copper(II) from a mixture of metal ions (Co(II), Ni(II), Cu(II)) when used as chromatographic stationary phase. The optimum pH appeared to be pH = 5.5 using acetate buffer as an eluent. Thermal analysis showed that the ligand system is very stable at relatively high temperatures.

Background: Effective wastewater treatments are paramount to modern-day Scientists. The available methods are ineffective in detoxifying tannery wastewater. Aim: This study synthesize and characterized polysiloxane-Immobilized thiosalicylic-mercaptoethanol ligand system (PITSMCBLS) and used in detoxification of Cr3+ and Fe3+ from tannery wastewater.Method: Porous solid PITSMCBLS was prepared by hydrolytic polycondensation of tetraethylorthosilicate with mixture of 3-chloropropyltrimethoxysilane, methanol and sodium hydroxide as catalyst. The gelation formed (3-CPP) after 40 min, was functionalized (F-3CPP) with excess ethylchloroacetate, triethylamine and grafted with thiosalicylic-mercaptoethanol bi-ligand. The PITSMCBLS was characterized using FTIR and SEM-EDX. The competitive sorption characteristics of metal ions (Cr3+ and Fe3+) were studied using Microwave Plasma Atomic-Emission Spectrophotometer.Result: The FTIR spectrum of PITSMCBLS showed vibrational frequencies (cm-1) at: 3...

Versatile heavy metal ions removal is performed via iron oxide core mesoporous silica shell nanocontainers functionalized with diethylene triamine pentaacetic acid. Magnetic separation from aqueous media is obtained for a dozen of the most toxic heavy metal ions with remarkable efficiencies. Furthermore, this study demonstrates enhancement of the adsorption capacities with the combination of porous and surface functionalization of the nanocontainers.

Versatile heavy metal ions removal is performed via iron oxide core mesoporous silica shell nanocontainers functionalized with diethylene triamine pentaacetic acid. Magnetic separation from aqueous media is obtained for a dozen of the most toxic heavy metal ions with remarkable efficiencies. Furthermore, this study demonstrates enhancement of the adsorption capacities with the combination of porous and surface functionalization of the nanocontainers.

An extraction chromatographic solid porous polysiloxane functionalized by chelating diethylenetriamine ligand of the general formula P-(CH 2 ) 3 -NH(CH 2 ) 2 NH(CH 2 ) 2 NH 2 , (Where P represents [Si-O] n siloxane network) has been evaluated for the separation of Co(II), Ni(II) and Cu(II) from aqueous solutions. The chromatographic parameters of the separation method have been optimized. The ligand system retained Co(II), Cu(II) and Zn(II) effectively when used as a metal ion extractant by controlling the pH value. The ligand system also shows a good separation of a mixture of metal ions Co(II), Ni(II) and Cu(II) when used as chromatographic stationary phase. The optimum separation pH values were 4.5, 4 for Co(II) and Ni(II) respectively, while a solution of 0.1 M HNO 3 was used to elute Cu(II). Metal ions were also preconcentrated at pH 5.5. The chemisorbed metal ions were regenerated from the solid extractant using 0.5 M HCl.