Subtle Interplay of Weak Intermolecular Interactions. Crystal Structures of Lead(II) Complexes with 4,4′‐Dimethyl‐2,2′‐bipyridine

Three adducts of the N,N′‐bidentate aromatic base 4,4′‐dimethyl‐2,2′‐bipyridine (dmbpy) of lead(II) salts, [Pb(dmbpy)₂(NO₃)₂] ( 1 ), [Pb(dmbpy)₂(ClO₄)₂] ( 2 ) and [Pb(dmbpy)(NCS)₂]_n ( 3 ) have been synthesized and characterized by elemental analysis, IR, ¹H‐NMR and ¹³C‐NMR spectroscopy and studied by thermal analysis as well as X‐ray crystallography. The single‐crystal structures of these complexes show that the 6s electrons of lead(II) constitute a stereochemically active lone pair (SALP). The coordination numbers of the Pb^II ions are eight and seven, respectively. The supramolecular features in these complexes are guided/controlled by weak directional intermolecular interactions.     

Flotation Separation of Lead with Sodium Nitrate‐Potassium Iodide‐Cetyltrimethyl Ammonium Bromide System

The flotation separation behavior of lead with Sodium Nitrate‐Potassium Iodide‐Cetyltrimethyl Ammonium Bromide system and the conditions for the separation of lead with other metal ions are studied in this research. With 0.1 M potassium iodide, 1.0 × 10^?2 M Cetyltrimethyl Ammonium Bromide and 1.0 g/10 mL of sodium nitrate, Pb(II) can form an ion‐association complex (PbI₄^2?) (CTMAB⁺)₂ and be separated completely from Zn(II), Fe(III), Co(II), Ni(II), Mn(II) and Al(III) by flotation at pH = 1.0–3.0.     

Highly Efficient and Selective Removal of Pb(II) ions by Sulfur-Containing Calcium Phosphate Nanoparticles

A facile one-step co-precipitation method was demonstrated to fabricate amorphous sulfurcontaining calcium phosphate (SCP) nanoparticles, in which the sulfur group was in-situ introduced into calcium phosphate. The resulting SCP exhibited a noticeable enhanced performance for Pb(II) removal in comparison with hydroxyapatite (HAP), being capable of easily reducing 20 ppm of Pb(II) to below the acceptable standard for drinking water within less than 10 min. Remarkably, the saturated removal capacities of Pb(II) on SCP were as high as 1720.57 mg/g calculated by the Langmuir isotherm model, exceeding largely that of the previously reported absorbents. Significantly, SCP displayed highly selective removal ability toward Pb(II) ions in the presence of the competing metal ions (Ni(II), Co(II), Zn(II), and Cd(II)). Further investigations indicated that such ultra-high removal efficiency and preferable affinity of Pb(II) ions on SCP may be reasonably ascribed to the formation of rodlike hydroxypyromorphite crystals on the surface of SCP via dissolution-precipitation and ion exchange reactions, accompanied by the presence of lead sulfide precipitates. High removal efficiency, fast removal kinetics and excellent selectivity toward Pb(II) made the obtained SCP material an ideal candidate for Pb(II) ions decontamination in practical application.     

Differential Pulse Polarographic Determination of Cd(II) and Pb(II) in Milk Samples after Solid‐Phase Extraction Using Amberlite XAD‐2 Resin Modified with 2,2′‐DPED3P

In the present paper novel column solid phase extraction procedure was developed for the determination of Cd(II) and Pb(II) in cows', goats', ewes', buffalos' and humans' milk samples using newly synthesized reagent 2,2′‐DPED₃P (2,2′‐{[1,2‐diphenylethane‐1,2‐diylidene]dinitrilo}diphenol) for preconcentration and separation prior to differential pulse polarography using amberlite XAD‐2 in the ranges of pH 4.0–5.0. The sorbed elements were subsequently eluted with 10 mL of 2 M HCl elutes were analysed by differential pulse polarography (DPP). The interference of foreign ions has also been studied. Effects of various instrumental parameters are investigated and received conditions are optimized. The total metal concentration of the milk samples in the study area were in the following ranges 0.030–0.090 μg L^?1 of Cd(II), 0.009–0.026 μg L^?1 of Pb(II) respectively. The limits of detections were found to be 0.020 and 0.024 μg L^?1 for Cd(II) and Pb(II) respectively by applying a preconcentration factor ～40. The proposed enrichment method was applied successfully for the determination of metal ions in cows', goats', ewes', buffalos' and humans' milk samples.     

Characterising lone-pair activity of lead(II) by 207Pb solid-state NMR spectroscopy: coordination polymers of [N(CN)2]- and [Au(CN)2]- with terpyridine ancillary ligands

A series of lead(II) coordination polymers containing [N(CN)₂]^? (DCA) or [Au(CN)₂]^? bridging ligands and substituted terpyridine (terpy) ancillary ligands ([Pb(DCA)₂] ( 1 ), [Pb(terpy)(DCA)₂] ( 2 ), [Pb(terpy){Au(CN)₂}₂] ( 3 ), [Pb(4′‐chloro‐terpy){Au(CN)₂}₂] ( 4 ) and [Pb(4′‐bromo‐terpy)(μ‐OH₂)_0.5{Au(CN)₂}₂] ( 5 )) was spectroscopically examined by solid‐state ²⁰⁷Pb MAS NMR spectroscopy in order to characterise the structural and electronic changes associated with lead(II) lone‐pair activity. Two new compounds, 2 and [Pb(4′‐hydroxy‐terpy){Au(CN)₂}₂] ( 6 ), were prepared and structurally characterised. The series displays contrasting coordination environments, bridging ligands with differing basicities and structural and electronic effects that occur with various substitutions on the terpyridine ligand (for the [Au(CN)₂]^? polymers). ²⁰⁷Pb NMR spectra show an increase in both isotropic chemical shift and span (Ω) with increasing ligand basicity (from δ_iso=?3090 ppm and Ω=389 ppm for 1 (the least basic) to δ_iso=?1553 ppm and Ω=2238 ppm for 3 (the most basic)). The trends observed in ²⁰⁷Pb NMR data correlate with the coordination sphere anisotropy through comparison and quantification of the Pb? N bond lengths about the lead centre. Density functional theory calculations confirm that the more basic ligands result in greater p‐orbital character and show a strong correlation to the ²⁰⁷Pb NMR chemical shift parameters. Preliminary trends suggest that ²⁰⁷Pb NMR chemical shift anisotropy relates to the measured birefringence, given the established correlations with structure and lone‐pair activity.     

Sorption of Pb(Ⅱ) on Mg-Fe Layered Double Hydroxide

Mg‐Fe layered double hydroxide (LDH) with a Mg/Fe molar ratio of 3:1 was synthesized by using a coprecipitation method and the sorption removal of Pb(II) by the LDH sample from Pb(NO₃)₂ solution was investigated. It was found that Mg‐Fe LDH showed a good sorption ability for Pb(II) from Pb(NO₃)₂ solution, indicating that the use of LDH as a promising inorganic sorbent for the removal of heavy metal ions is possible. The sorption kinetics and the sorption isotherm of Pb(II) on the LDH sample obeyed the pseudo‐second order kinetic model and Aranovich‐Donohue equation, respectively. The sorption mechanism of Pb(II) on the LDH may be attributed to the surface‐induced precipitation and the chemical binding adsorption, and the removal ability arising from the surface‐induced precipitation is much higher than that from the chemical binding adsorption.     

Tubular bimetal oxysulfide CuMgOS catalyst for rapid reduction of heavy metals and organic dyes

Tubular bimetal oxysulfide CuMgOS catalyst was prepared using a feasible method at a low process temperature of 95°C. X‐ray diffractometry, X‐ray photoelectron spectrometry, field emission‐scanning electron microscopy, transmission electron microscopy, UV–Vis diffuse reflectance spectroscopy, photoluminescence emission spectrum, and nitrogen adsorption–desorption isotherms were used for CuMgOS characterizations. The CuMgOS reduction activities were investigated through the reduction of heavy metals of Cr (VI), Pb (II) and Hg (II) solutions, and the organic dyes of rhodamine‐B (RhB), methyl orange (MO) and methylene blue (MB) solutions under dark. The results showed that the CuMgOS prepared with an appropriate N₂H₄ amount for a suitable Cu (I)/Cu (II) ratio exhibited fast reduction activity without adding any reagents, with which the 100 mL Cr (VI), Pb (II) and Hg (II) solutions of 50 ppm were 100% reduced by 20 mg CuMgOS within 4 min, 6 min and 4 min, respectively. The 100 mL RhB, MO and MB solutions of 50 ppm were 100% reduced by 10 mg CuMgOS within 4 min, 5 min and 1 min, respectively, under the existence of NaBH₄. CuMgOS displayed excellent chemical stability for the re‐use tests on heavy metal ions and organic dyes. The excellent performance is attributed to CuMgOS bimetal oxysulfide catalyst with active surface reaction centers to interact with reactants, and the carrier hopping between Cu (I) and Cu (II).     

Synthesis and Crystal Structure of a Novel Polymeric Lead(II) Compound: [Pb2(phen)2(N3)3(ClO4)]n

A 2D lead(II) coordination polymer [Pb₂(phen)₂(N₃)₃(ClO₄)]_n,( 1 ) containing 1,10‐phenanthroline (phen) and two different anions, has been synthesized and characterized by elemental analysis, IR and ¹H NMR spectroscopy and X‐ray crystallography. The single‐crystal X‐ray data show two different kinds of Pb²⁺ ions with coordination numbers of eight, Pb1 = PbN₆O₂ and Pb2 = PbN₈, with hemidirected and holodirected structures, respectively. The supramolecular features in 1 is negiotated through the weak but directional C‐H···O and C‐H···N interactions and aromatic π–π stacking interactions.     

Different Coordination Modes of Saccharin in the Complexes of Lead(II) with 2‐Pyridylmethanol and Pyridine‐2, 6‐dimethanol — Synthesis,Spectral and Structural Characterization

New lead(II)‐saccharin complexes, [Pb(sac)₂(pym)] (1) and [Pb(sac)₂(pydm)] (2) (sac = saccharinate anion; pym = 2‐pyridylmethanol; pydm = pyridine‐2, 6‐dimethanol) were synthesized and characterized by IR spectroscopy and single crystal X‐ray diffractometry. Complex 1 crystallizes in the monoclinic P2₁/c space group with Z = 4, while the crystals of complex 2 are extremely X‐ray sensitive and decompose by the X‐ray beam within one day. Pym and pydm act as bi‐ and tridentate ligands, respectively. Most important feature of the complexes is non‐equivalent coordination of the sac ligands to the lead(II) atom. In the complex 1 , the sac ligands coordinate to the lead(II) ion in two distinct manners. One sac ligand behaves as a bridge between the lead(II) atoms through its N and carbonyl O atoms, whereas the other sac ligand acts as a bidentate chelating ligand through its N and carbonyl O atoms which is bicoordinating and also bridges the metal atoms to achieve the seven‐coordination. The structure is built up of three‐dimensional chains formed by the bridging of the PbN₃O₂ units and also held intermolecular hydrogen bonds. The IR spectra of the complexes were discussed in detail.     

A One‐dimensional Lead(II) Coordination Polymer with Bridging Saccharinate and 2‐Aminomethylpyridine Ligands: Synthesis,IR Spectra,and Crystal Structure of [Pb(ampy)(μ‐sac)2]n

A complex with eight‐coordinate lead(II ) atom and saccharinate (sac) and 2‐aminomethylpyridine ligands was characterized by IR, elemental analysis and X‐ray crystallography. The lead(II ) complex crystallizes in the monoclinic crystal system with space group P2₁/c. The single crystal X‐ray analysis shows that the complex is a coordination polymer, [Pb(ampy)(μ‐sac)₂]_n, in which the lead(II ) ions have a highly distorted bicapped trigonal antiprism coordination. Lead(II ) ions are bridged by carboxyl groups of sac forming one‐dimensional linear chains, running parallel to the a axis. The intrachain Pb···Pb distances are 4.4490(3) and 4.4679(3)Å. The individual chains are connected by N—H···O_sulfonyl and C_ampy—H···O_sulfonyl type hydrogen bonds, resulting in a three‐dimensional network. The sac ligand acts as bidentate and bridging ligand, while ampy behaves as an N, N′ donor. The IR spectra of the lead(II ) complex are discussed in detail.     

Synthesis and Spectroscopic Characterization of New Lead(II) Thiosaccharinates. Molecular Structure of Bis(thiosaccharinato)tetrakis(pyridine)dilead(II) and Thiosaccharinato‐bis(1,10‐phenantroline)lead(II) Thiosaccharinate

Four new lead(II) thiosaccharinate complexes: [Pb(tsac)₂H₂O] (1) (tsac: thiosaccharinate anion), [Pb₂(tsac)₄(py)₄] (2) (py: pyridine), [Pb(tsac)(o‐phen)₂](tsac)·CH₃CN (3) (o‐phen: 1,10‐phenantroline), and [Pb(tsac)₂(bipy)] (4) (bipy: 2,2′‐bipyridine) were prepared. The infrared and electronic spectra as well as the thermal analysis of all the compounds were recorded and discussed. The thiosaccharinate anion acts in three different coordination forms, one of then reported for the first time. The crystal structures of complexes 2 and 3 have been determined by single crystal X‐ray diffractometry. In complex 2 , two monomeric moieties are joined together forming a symmetric bis‐μ‐sulphur bridged dimer by interaction of two lead(II) atoms through the exocyclic sulphur atoms of two thiosaccharinate ligands. The seven‐fold coordination sphere of each lead atom is completed by two pyridine nitrogen atoms and by another sulfur and two nitrogen atoms of the thiosaccharinate anions. In complex 3 , the lead(II) atom is coordinated by four nitrogen atoms of two 1,10‐phenantroline molecules and by the sulfur and nitrogen atoms of one thiosaccharinate ion. The second anion has an electrostatic interaction with the nucleus.     

The Crystal and Molecular Structures of Pb(II) Complexes with Furan-2-Carboxylate and Furan-3-Carboxylate Ligands

The crystals of Pb(II) 2-furancarboxylate (title compound I) contain tetrameric structural units Pb₄(2-FCA)₈(H₂O₂) in which four Pb(II) ions are bridged by carboxylate oxygen atoms forming a circular moiety. In addition, pairs of Pb(II) ions are bridged by carboxylate oxygen atoms inside this moiety. The molecular pattern observed in Pb(II) 3-furancarboxylate (title compound II) is polymeric. It consists of Pb(3-FCA)₂(H₂O) structural units bridged by carboxylate oxygen atoms donated by the furan-3-carboxylate (3-FCA) ligands which are bidentate, using both their carboxylate oxygen atoms for chelation. The coordination around Pb(II) ions is eightfold and ninefold including, apart from carboxylate oxygen atoms, a water oxygen atom and oxygen atoms donated by the furan rings of the ligand molecules. Hydrogen bonds with the water molecule as the donor operate between adjacent ligand molecules. The stereochemical activity of the lone 6s ² electron pair on the Pb(II) is observed in title compound II.     

Development of Polymeric Resin Ion‐exchanger Based Chloride Ion‐selective Electrode for Monitoring Chloride Ion in Environmental Water

A chloride ion‐selective electrode (ISE) membrane was developed by using a copolymeric ion‐exchanger resin (trimethyl ethenyl quaternary ammonium chloride polystyrene‐divinylbenzene copolymer resin, TMEQAC PSDVB), the ionophore ({μ‐[4,5‐Dimethyl‐3,6‐bis(dodecyloxy)‐1,2‐phenylene]}bis(mercury chloride), ETH9033), the plasticizer (bis(2‐ethylhexyl) sebacate, DOS), and the membrane substrate (polyvinylchloride, PVC). At 25 °C, the electrode exhibited an ideal Nernstian response of 59.2 mV/decade with the linear calibration concentration range from 1.0 × 10^?4‐1.0 × 10^?2 M (r² = 0.9930). The limit of detection was 2.45 ppm (6.9 × 10^?2 mM) and the measurement response time was less than 10 seconds. The working temperature range of electrode was 10‐45 °C. The working pH range for chloride ion measurement was 2.0‐11.0. Among the various anions examined in this work, only I^?, SCN^?, and MnO₄^? ions show significant interference to the electrode measurement. The chloride ISE can be used at least 72 days. The determination of chloride ion content in three kinds of environmental water sample with the electrode method was accurate (92‐95%) and precise (RSD < 4.4%) and did not show significance difference from the high‐performance liquid chromatography method.     

The 4‐(Dimethylamino) benzaldehyde‐4‐ethylthiosemicarbazone as Ionophore for Mercury(II) Solid State Selective Electrode

Hg(II) has formed a soluble complex with 4‐(dimethylamino) benzaldehyde‐4‐ethylthiosemicarbazone (DMABET) in methanol with a molar ratio of mercury(II):DMABET of 1 : 4. The formation constant (K_f) and Gibbs free energy (?G) of the complex showed that the formation of the complex was favorable. The DMABET was investigated as ionophore for Hg(II)‐ion selective electrode (ISE). At optimum pH 1–5 the proposed Hg(II)‐ISE showed an almost Nernstian slope at 27.8±1 mV, with linear regression coefficient, R²=0.995 and a detection limit of 5×10^?6 M. There was no serious interference from silver(I) with selectivity coefficient 5.69×10^?3. The electrode life span was more than 3 months. It has been applied for real water sample analysis and the results were in good agreement with the standard method.     

Determination of Pb(II) and Cu(II) by Electrothermal Atomic Absorption Spectrometry after Preconcentration by a Schiff Base Adsorbed on Surfactant Coated Alumina

1,2-Bis（salicylidenamino）ethane loaded onto sodium dodecyl sulfate-coated alumina was used as a new chelating sorbent for the preconcentration of traces of Pb（Ⅱ） and Cu（Ⅱ） prior to atomic absorption spectrometric determination. The influence of pH, flow rates of sample and eluent solutions, and foreign ions on the recovery of Pb（Ⅱ） and Cu（Ⅱ） by this sorbent has been studied. The retained ions were eluted with 4 mol·L nitric acid and determined by electrothermal atomic absorption spectrometry （ETAAS）. The data of limit of detection （3σ） for Pb（Ⅱ） and Cu（Ⅱ） were found to be 8.57 and 2.69 ng·L^-1 respectively, while the enrichment factor for both ions was 100. The proposed method was successfully applied to determination of lead and copper in different water samples.     

Permetalloplumbanes: Preparation of [Pb{Co(CO)3(L)}4] and [Pb{Fe(CO)2(NO)(L)}4].: Complexes containing four transition metal to lead bonds (L = tertiary arsine,phosphine or phosphite).

The sole and unexpected products from the reactions of a variety of lead (II) and lead (IV) compounds with [Co₂(CO)₆(L)₂] complexes (L = tertiary arsine, phosphine, or phosphite) in refluxing benzene solution are the blue, air-stable percobaltoplumbanes [Pb{Co(CO)₃(L)}₄]. These have also been obtained from the reaction of Na[Co(CO)₃(L)] (L  PBu₃ⁿ) with lead (II) acetate which with Na[Fe(CO)₂(NO)(L)] forms the isoelectronic [Pb{Fe(CO)₂(NO)(L)}₄] [L  P(OPh)₃]. The IR spectra of the complexes in the v(CO) and v(NO) regions are consistent with tetrahedral PbCo₄ or PbFe₄ fragments, trigonal bipyramidal coordination about the cobalt or iron atoms and linear PbCoAs, PbCoP, or PbFeP systems. Unlike [Pb{Co(CO)₄}₄], our complexes do not dissociate to [Co(CO)₃(L)]^? or [Fe(CO)₂(NO)(L)]^? ions when dissolved in donor solvents.     

Spectrophotometric determination of copper(II) using oximidobenzotetronic acid

Summary Oximidobenzotetronic acid (OBTA) is proposed as a sensitive spectrophotometric reagent for the estimation of 0.5–3.0 ppm of copper(II) at 427 nm in 50% dioxan at p_H 5.3–7.5. For the estimation of 2 ppm Cu(II), 1.3 ppm Ni(II), 1.3 ppm Co(II), 3.2 ppm Fe(II), 10.3 ppm Fe(III), 9.7 ppm Ce(IV), 300 ppm acetate, 160 ppm oxalate, 95 ppm tartrate, 50 ppm citrate, as well as Zn(II), Cd(II), Hg(II)) Pb(II), Mn(II), As(III) as well as (V), Th(IV), Be(II), Ce(III), La(III), V(V) and Mo(VI), even when present in large quantities, do not interfere. The interference due to 25 ppm Bi(III), 20 ppm Sb(III), 20 ppm Sn(II), 25 ppm Sn(IV) and 30 ppm W(VI) can be removed by the addition of 95 ppm tartrate ions.

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Zusammenfassung Oximidobenzotetronsäure wurde als empfindliches Reagens zur spektrophotometrischen Bestimmung von 0,5 bis 3,0 ppm Kupfer(II) bei 427 nm in 50%iger Dioxanlösung bei p_H 5,3 bis 7,5 vorgeschlagen. Die Anwesenheit von 1,3 ppm Ni(II), 1,3 ppm Co(II), 3,2 ppm Fe(II), 10,3 ppm Fe(III), 9,7 ppm Ce(IV), 300 ppm Acetat, 160 ppm Oxalat, 95 ppm Tartrat, 50 ppm Citrat sowie die Anwesenheit auch großer Mengen Zn(II), Cd(II), Hg(II), Pb(II), Mn(II), As(III) bzw. (V), Th(IV), Be(II), Ce(III), La(III), V(V) und Mo(VI) stören die Bestimmung von 2 ppm Cu(II) nicht. Der störende Einfluß von 25 ppm Bi(III), 20 ppm Sb(III), 20 ppm Sn(II), 25 ppm Sn(IV) und 30 ppm W(VI) kann durch Zusatz von 95 ppm Tartrat beseitigt werden.

     

Test Determination of Lead and Zinc in Water with the Use of Xylenol Orange Immobilized on Silica

Xylenol Orange immobilized on silica as a complex of iron(III) was used for the test determination of lead(II) and zinc(II) in drinking water over concentration ranges of 10–100 and 13–130 g/L, respectively. The maximum distribution coefficients were found to be 7.50 × 10³ mL/g for Pb and 3.75 × 10³ mL/g for Zn. The macro main trace components of water at a level of their maximum permissible concentrations caused no interference. Al(III), Fe(III), and Zn(II) in the presence of NH₄F did not interfere with the determination of Pb(II), whereas lead in the presence of acetate caused no interference with the determination of Zn(II).     

Highly efficient removal of toxic lead ions from aqueous solutions using a new magnetic metal‐organic framework nanocomposite

A magnetic metal‐organic framework (MOF) nanocomposite was successfully prepared by a new and green strategy through reasonable design. Magnetic MOF of Fe₃O₄‐NHSO₃H@HKUST‐1 nanocomposite use for removal of lead ions as an environmental pollutant. The experimental results indicated that the nano adsorbent of Fe₃O₄‐NHSO₃H@HKUST‐1 can removed lead ions under optimum operational conditions. The dosage of the nanocomposite, pH of the sample solution, and contact time were obtained to be 10 mg, 7.0, and 90 min, respectively, while the initial concentration of Pb(II) ions of 400 mg/L was used. A kinetic study indicated that a pseudo‐second‐order model agreed well with the experimental data. The isotherm experiments revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The maximum adsorption capacity of the adsorbent for the removal of lead under the optimum operational conditions of pH 7.0 and temperature 25°C was found to be 384.6 mg/g. The thermodynamic parameters indicate that the adsorption of lead is spontaneous and endothermic. The magnetic MOF nanocomposite could be recovered easily and reused many times without significant loss of its nano‐adsorbent activity. The proposed method is simple, eco‐friendly, low cost, and efficient in the removal of lead ions from aqueous solutions.     

Ethyl­ammonium and diethyl­ammonium salts of chloranilic acid

In the crystals of two title salts of chloranilic acid (2,5‐di­chloro‐3,6‐di­hydroxy‐p‐benzo­quinone), namely ethyl­ammonium chloranilate, C₂H₈N⁺·C₆HCl₂O₄^?, (I), and diethyl­ammonium chloranilate, C₄H₁₂N⁺·C₆HCl₂O₄^?, (II), the chloranilate ions are present as a hydrogen‐bonded dimer which has an inversion center. The ethyl­ammonium and diethyl­ammonium ions link the dimers through N—H?O hydrogen bonds, forming a three‐dimensional hydrogen‐bond network in (I) and a one‐dimensional chain in (II).