Chelation Ion Chromatography on DMSO Impregnated Silica Gel-G Layers: Specific Separation of Cd2+, W6+, and Zr4+ from Transitional Metal Ions

Abstract

Chelation ion chromatography of metal ions on DMSO impregnated silica gel-G layers in ether; DMSO: 1M HNO₃ (1:1); n-butanol: acetone: HNO₃ (6:6:1) and di-isopropyl ether: DMSO: THF systems having varying compositions, was performed. The zero R_f for a number of cations is explained in terms of precipitation and strong adsorption. It was possible to separate Cd²⁺, W⁶⁺, Zr⁴⁺, Zn²⁺ and VO²⁺ from numerous metal ions. A number of analytically important binary and ternary separations were also achieved and were found useful in synthetic alloy analysis.     

Electrochromatographic Separation of DMSO Complexes of Metal Ions

Abstract

Electrochromatography of DMSO complexes of fourteen metal ions have been performed in five electrolytes at 100 volts for 3 hrs. The mechanism of migration has been explained and a number of separations of metal-DMSO complexes were achieved.     

Paper Chromatographic Separation of DMSO Complexes of Metal Ions

Abstract

R_f, values of DMSO complexes of some metal ions in twelve solvent systems are given. The separation of Zn and Hg DMSO complexes from others have been achieved in Water and in n-butyl alcohol respectively by using paper chromatography. Some other possible separations are also reported.     

Analysis of Nonionic Surfactants by High Performance Liquid Chromatography

Abstract

This review discusses the principles of immobilized metal ion affinity chromatography (IMAC) and its applications to protein separations. IMAC functions by binding the accessible electron-donating pendant groups of a protein - such as histidine, cysteine, and tryptophan - to a metal ion which is held by a chelating group covalently attached on a stationary support. A common chelating group is iminodiacetate. The ions commonly used are of borderline or soft metals, such as Cu²⁺, Ni²⁺, Co²⁺, and Zn²⁺. Protein retention in IMAC depends on the number and type of pendant groups which can interact with the metal. The interaction is affected by a variety of independent variables such as pH, temperature, solvent type, salt type, salt concentration, nature of immobilized metal and chelate, ligand density, and protein size. Proteins are usually eluted by a decreasing pH gradient or by an increasing gradient of a competitive agent, such as imidazole, in a buffer. There are still several unresolved issues in IMAC. The exact structures of protein-immobilized metal complexes need to be known so that retention behavior of proteins can be fully understood and sorbent structures can be optimized. Engineering parameters, such as adsorption/desorption rate constants, sorbent capacities, and intraparticle diffusivities, need to be developed for most protein systems. Engineering analysis and quantitative understanding are also needed so that IMAC can be used efficiently for large scale protein separations.     

Effect of hydrogen bonding of solvent on the thermodynamic stability of cadmium ethylenediamine complexes

Changes in the stability of the cadmium(ii) ethylenediamine complexes in mixed water—DMSO solvents were studied by pH-metry and calorimetry. Complex cations [Cd(en)]²⁺, [Cd(en)₂]²⁺, and [Cd(en)₃]²⁺ are formed in aqueous solutions, and the [Cd(en)₄]²⁺ complex with a partially dentate ligand is stable in DMSO. An increase in the DMSO content in a solvent increases the stability of the complexes. The maximum increase in logK is observed for coordinatively saturated compounds. The thermodynamics of complexation is discussed from the viewpoint of solvation approach. Principal differences in the influence of aqueous-alcohol and aqueous-aprotic solvents on the stability of the metal amino complexes were revealed. Protolytic solvents exert a destabilizing effect on the multiligand complexes, because the coordination sphere is involved in H bonding.     

Synthesis and luminescence of polymeric metal complexes based on 1,10-phenanthroline and 8-hydroxyquinoline

A ligand containing different coordination groups, 5-([1,10]phenanthroline-[4,5-f]imidazo-2-yl)-8-hydroxyquinoline (PhenI8Q) has been synthesized and two corresponding polymeric metal complexes Cu(II) (1) and Zn(II) (2) were prepared by coordination polymerization of the ligand with copper(II) and zinc(II) halides, respectively. The ligand was characterized by ¹H-NMR, ¹³C-NMR, and Fourier transform-infrared (FT-IR) and its corresponding polymeric metal complexes 1 and 2 were characterized by FT-IR, UV-Vis, elemental analysis, thermal gravimetric analysis, and conductivity measurements. The absorption spectra and luminescence of the ligand, 1, and 2 were investigated by UV-Vis and fluorescence spectroscopy at room temperature. Compared with the ligand, the fluorescence spectra of the polymeric metal complexes exhibit blue shifts in dimethyl sulfoxide (DMSO) solution and bathochromic shifts in the solid state. Complexes 1 and 2 emit blue light with emission maximum (λ _{f max}) at 449 and 431 nm in DMSO solution and at 485 and 484 nm in the solid state, respectively.     

Dimethyl sulfoxide as an O-donor ligand in tetravalent actinide complexes

Four new perchlorate complexes of tetravalent actinides with dimethyl sulfoxide (DMSO) molecules (An⁴⁺ = Th, U, Np, Pu) are synthesized and studied. According to the X-ray diffraction data, compounds [Th(DMSO)₉](ClO₄)₄ · 2CH₃CN (I), [U(DMSO)₈](ClO₄)₄ · CH₃CN (II), [Np(DMSO)₈](ClO₄)₄ · CH₃CN (III), and [Pu(DMSO)₈](ClO₄)₄ · CH₃CN (IV) crystallize in the triclinic crystal system (space group P1). The crystals of compounds II–IV are isostructural. The absorption spectra of the complexes in the IR and visible regions are measured. All compounds exhibit a decrease in the frequencies of stretching vibrations ν(SO) over the spectrum of free DMSO, indicating the formation of the O-bonded complexes of An⁴⁺. The optical spectra of the crystalline compounds exhibit shifts of the bands of electronic f-f transitions of the An⁴⁺ ions relative to the hydrated ions: the bathochromic shifts for the U and Np complexes and the hypsochromic shift for the Pu complex. The first coordination sphere of the actinide atoms in the studied complexes is highly stable.     

Synthesis,characterization, reactivity,and electrochemical studies of manganese(IV) complexes of bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone

Manganese(IV) complexes [Mn^IV(npah)(H₂O)₂] (1) and [Mn^IV(npah)(A)₂]?·?nH₂O (where A?=?py (2), 2-pic (3), 3-pic (4), 4-pic (5)) and Mn^IV(npah)(NN)] (NN?=?bpy (6) and phen (7)) have been synthesized from bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone in methanol. The composition of the complexes has been established by elemental analyses. Complex 3 has been characterized by mass spectral data also. Structural assessment of the complexes has been based on data from molar conductance, magnetic moment, electronic, electron paramagnetic resonance, and infrared (IR) spectral studies. Molar conductances of the complexes in DMSO suggest non-electrolytes. Magnetic moment and EPR studies suggest +4 oxidation state for manganese in these complexes. Electronic spectral studies suggest six-coordinate octahedral geometry around the metal ions. IR spectra reveal that H₄npah coordinates to the metal in enol form. Reaction of the complexes with benzyl alcohol and SO₂ has been investigated. Cyclic voltammetric studies of the complexes have also been carried out.     

ADDUCTS OF THEOBROMINE WITH 3d METAL PERCHLORATES

Abstract

Adducts of theobromine (tbH) with 3d metal perchlorates (Mⁿ⁺ = Cr^3-. Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn^2- I here prepared by refluxing mixtures of the Iigand and a metal salt in ethyl acetate-triethyl orthoformate. The new complexes invariably involve 2: 1 molar ratios of tbH to metal ion and are apparently monomeric with terminal tbH ligands binding riaa ring nitrogen (N9 or Nl). The Mn²⁺, Cu²⁺ and Zn^2- complexes are distorted tetrahedral, involving tuo tbH and two unidentate perchlorato ligands in the first coordination sphere of the metal ion. The remaining metal(II) complexes (Fe, Co, Ni) were obtained as monohydrates. These compounds are pentacoordinated of the [M(tbH)₂(OClO₃)₂(OH₂)] type, containing one aqua ligand in addition to the tbH and perchlorato ligands. The Cr³⁺ and Fe³⁺ complexes are low-symmetry hexacoordinated, with two tbH ligands. two unidentate and one bidentate chelating perchlorate Iigands.     

Complexation Studies of Bidentate Heterocyclic N-Donor Ligands with Nd(III) and Am(III)

A new bidentate nitrogen donor complexing agent that combines pyridine and triazole functional groups, 2-((4-phenyl-1H-1,2,3-triazol-1-yl)methyl)pyridine (PTMP), has been synthesized. The strength of its complexes with trivalent americium (Am³⁺) and neodymium (Nd³⁺) in anhydrous methanol has been evaluated using spectrophotometric techniques. The purpose of this investigation is to assess this ligand (as representative of a class of similarly structured species) as a possible model compound for the challenging separation of trivalent actinides from lanthanides. This separation, important in the development of advanced nuclear fuel cycles, is best achieved through the agency of multidentate chelating agents containing some number of nitrogen or sulfur donor groups. To evaluate the relative strength of the bidentate complexes, the derived constants are compared to those of the same metal ions with 2,2′-bipyridyl (bipy), 1,10-phenanthroline (phen), and 2-pyridin-2-yl-1H-benzimidazole (PBIm). At issue is the relative affinity of the triazole moiety for trivalent f element ions. For all ligands, the derived stability constants are higher for Am³⁺ than Nd³⁺. In the case of Am³⁺ complexes with phen and PBIm, the presence of 1:2 (AmL₂) species is indicated. Possible separations are suggested based on the relative stability and stoichiometry of the Am³⁺ and Nd³⁺ complexes. It can be noted that the 1,2,3-triazolyl group imparts a potentially useful selectivity for trivalent actinides (An(III)) over trivalent lanthanides (Ln(III)), though the attainment of higher complex stoichiometries in actinide compared with lanthanide complexes may be an important driver for developing successful separations.     

Synthesis and DFT calculations of new ruthenium(II) nitrosyl complexes using cis-fac-dichlorotetrakis(dimethylsulfoxide)ruthenium(II) precursor and different oximes as sources of nitrosyl ligand

Abstract

Three NO⁺-ruthenium(II) complexes were prepared by using cis-[RuCl₂(DMSO)₄] as precursor, P, and the compounds benzohydroxamic acid (BHA), 1′, anti-diphenylglyoxime (H₂dpg), 2′, and dimethylglyoxime (H₂dmg), 3′, as sources of NO moiety. The three complexes [RuCl₂(DMSO)₃(NO)]⁺(BA)^?, 1, [RuCl₂(DMSO)₃(NO)]⁺(Hdpg)^?, 2, and [RuCl₂(DMSO)₃(NO)]⁺(Hdmg)^?, 3, were characterized by (FT-IR, NMR, UV-Vis) spectroscopy, thermogravimetry, and microanalysis. From FT-IR spectral data, two modes of coordination of DMSO to Ru atom through both S and O atoms were detected for 1 and 2. For 3, only S coordination was reported. Computational studies on the [RuCl₂(DMSO)₃(NO)]⁺ cationic parts, 1″, 2″ and 3″, of the investigated complexes 1, 2 and 3 were carried out by DFT. The molecular geometry and mode of attachment of Ru(II) with DMSO were performed with the B3LYP/LANL2DZ level of theory and basis set. Theoretical to the experimental agreement was achieved for analysis of IR data of the investigated complexes. Additional information about binding between the ruthenium atom and the DMSO ligand has been obtained by NBO analysis.     

Templated Synthesis of Copper(II) Azacyclam Complexes Using Urea as a Locking Fragment and Their Metal‐Enhanced Binding Tendencies towards Anions

Copper(II) azacyclam complexes 3 ²⁺ and 4 ²⁺ were obtained through a metal‐templated procedure involving the pertinent open‐chain tetramine, formaldehyde and a phenylurea derivative as a locking fragment. Both metal complexes can establish interactions with anions through the metal centre and the amide NH group. Equilibrium studies in DMSO by a spectrophotometric titration technique were carried out to assess the affinity of 3 ²⁺ and 4 ²⁺ towards anions. While the NH group of an amide model compound and the metal centre of the plain Cu^II(azacyclam)²⁺ complex do not interact at all with anions, 3 ²⁺ and 4 ²⁺ establish strong interactions with oxo anions, profiting from a pronounced cooperative effect. In particular, 1) they form stable 1:1 and 1:2 complexes with H₂PO₄^? ions in a stepwise mode with both hydrogen‐bonding and metal–ligand interactions, and 2) in the presence of CH₃COO^?, they undergo deprotonation of the amido NH group and thus profit from axial coordination of the partially negatively charged carbonyl oxygen atom in a scorpionate binding mode.     

On the metal ion selectivity of PNP-lariat ether—an insight from density functional theory calculations

The complexes of Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺, and Ca²⁺ metal cations with [N₃P₃R₄O(CH₂CH₂O)₄] (R?=?H(1), NMe₂(2), NC(NMe₂)₂(3)) PNP-lariat ethers were systematically studied in the gas phase by using density functional theory (DFT) B3LYP-D3/6-311+G(3df,2p)//B3LYP/6-31+G(d,p) method. The gas phase cation affinities were calculated to span the wide range between 64.2 and 496.1 kcal mol^?1 in order K⁺?<?Na⁺?<?Li⁺?<?Ca²⁺?<?Mg²⁺?<?Be²⁺. The structural and electronic properties of 1–3 and their complexes were investigated and effects of electron-donor substituents were analyzed. The electron-donor substituents were found to promote the cation affinity. Sidearm coordinative interaction with the crown ether-complexed metal ion has been noticed. The nature of the metal–ligand interactions was investigated using Bader’s Quantum theory of atoms in molecule. It has been found that the Be²⁺–N bonds are partly covalent in nature while other coordinate bonds are of the electrostatic nature. The electron density at the bond critical points was found to be consistent with cation affinity. Natural bond orbital analysis was performed on the optimized geometries. The results showed that the stabilization interaction energies are caused by the donation of O/N lone pair electrons to the LP* orbitals of the metal cations. The amount of charge transfer follows the cation affinity order. The largest charge transfer and associated second-order perturbation stabilization energy were observed for Be²⁺ complexes.

     

Polarographic and spectrophotometric studies of the spiro[indolin-pyridobenzopyrane] complexes with the heavy metal ions

By means of the cathode differential pulse polarography on a mercury drop electrode the reactions of Zn²⁺, Cd²⁺, and Pb²+ ions with the spiro[pyridobenzopyranes] of the indoline series in DMSO were studied. Tetrabutylammonium perchlorate was used as the background electrolyte. It is found that well soluble heavy metal complexes of the spiro[indolin-pyridobenzopyranes] are formed in DMSO. The number of ligands, the step and the general stability constants of the obtained complex compounds are evaluated. The distribution curves of all the complexes under investigation are plotted. The spiropyrane complexes were also studied by means of the spectrophometric method. Good agreement of the results obtained by two different methods was established.     

Quantitative Separation of Hg(11) From Several Metal Ions on Zr(IV) Antimonate Papers

Abstract

The chromatographic behaviour of 32 metal ions has been studied on paper Impregnated with Zirconium(IV) antimonate in aqueous HCI and mixed solvent system containing dimethyisul phoxide and dioxane. Several Important binary and ternary separations have been achieved. Quantitative separation of Hg(ll) from Ni²⁺, Pb²⁺, Pd²⁺, Ru³⁺, Rh³⁺, Bi³⁺, Co²⁺, Cd²⁺ and Gd³⁺ is described.     

Benzoylation and Properties of 14-π Nickel(II)-Tetraazaannulene Complexes with Substituents on the Phenyl Ring

The benzoylated asymmetrical nickel(II) complexes, 2,4,9,11-tetramethyl-3,10-dibenzoyl-1,5,8,12-([14]-Xbenzo)tetraazacyclotetradecinato(2-)nickel(II) ( A_1-4) and 2,4,10,12-tetramethyl-3,11-dibenzoyl-1,5,9,13-([15]-Xbenzo)tetraazacyclotetradecinato(2-)nickel(II) (B_1-4), wherein X = CH₃(A₁ and B₁), H ( A₂ and B₂), Cl (A₃ and B₃) and NO₂(A₄ and B₄), have been synthesized and characterized by analysis, IR, electronic, ¹H- and ¹³C-NMR spectra. An intense IR band due to C=O stretching is present in the range 1630-1650 cm^-1 upon benzoylation. Electronic spectra show bands at 375-390 nm with k_max = 10000-26000 M^-1cm^-1 due to π→π* transitions of macrocycles and at 500-550 nm with k_max = 1000-5000 M^-1cm^-1 attributable to LMCT for each of the complexes. The proton peaks of methine sites in the NMR spectra disappear on benzoylation. Results of the carbon-13 NMR spectra are compatible with those of the proton NMR. Cyclic voltammograms of the complexes in acetonitrile exhibit two successive and reversible (irreversible in DMSO) oxidation peaks for the macrocycle (Mc M Mc ^{” +} and Mc ^{” +} M Mc ²⁺) in the ranges +0.31 - +0.51 and +0.60 - +0.84 V, respectively. In the reduction area, a reversible wave is followed by reduction of metal {Ni(II) M Ni(I) at around m 2.32 V}. Unlike analogous complexes without the benzoyl group, those compounds are not electropolymerized by cyclic voltammetry.     

Solvent-Assisted Naked Eye Sensing of Hg2+ by a Chemoreceptor Derived from Diazocoupling of Sulfathiazole with Diethyl Malonate

Abstract

2-{[4-(Thiazol-2-ylsulfamoyl)-phenyl]-hydrazono}-malonic acid diethyl ester (R1) and 2-{[4-(5-methyl-isoxazol-3-ylsulfamoyl)-phenyl]-hydrazono}-malonic acid diethyl ester (R2) were synthesized through diazocoupling of sulfathiazole and sulfamethoxazole, respectively, with diethyl malonate. They were characterized through various spectroscopic and mass spectral studies. R2 was also characterized through a single crystal X-ray diffraction (XRD) study. Only R1 selectively recognized Hg²⁺ from a wide range of metal ions through naked-eye change. A color change from orange to olive green was observed upon addition of 1.0 equivalent of Hg²⁺ as its chloride salt to the 1 × 10^?3 M DMSO solution of R1. The role of DMSO in the sensing process appears to be the crucial one, because the solvent-assisted band of R1 at 482 nm observed in its UV-Vis spectrum in DMSO did not appear in its spectra recorded in nujol or in a polar aprotic solvent. The UV-Vis and ¹H NMR titrations revealed that the formation of six-membered 1:1 chelate between R1 and Hg²⁺ triggering the desolvation of R1

as the key step towards its sensing activity. The determination of binding stoichiometry between R1 and Hg²⁺ along with binding constant has also been discussed.

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GRAPHICAL ABSTRACT      

C–H···Onitrate synthon assisted molecular assembly of hydrogen bonded Ni(II) and Cu(II) complexes

Two Schiff base metal complexes [Cu–SPETN·NO₃ (1) and Ni–SPETN·NO₃ (2) [SPETN?=?2,2′-[propane,1,3-diylbis(nitrilomethyldyne)pyridyl,phenolate]] with hydrogen bonding groups have been synthesized and characterized by single-crystal X-ray diffraction. In both of the compounds nitrates occupy a crystallographic general position. In 1 the lattice nitrates are on the 2₁ screw axis while in 2 they are at the crystallographic inversion center. C–H···O_nitrate synthons (formed by the nitrate anions and peripheral hydrogen bonding groups of the metal complexes) are non-covalent building blocks in molecular-assembly and packing of the cationic Schiff base metal complexes (M?=?Ni²⁺, Cu²⁺), resulting in 2-D hydrogen bonded networks. The Cu···Cu non-bonding contact in 1 is 3.268?Å while the Ni–Ni bonding distance in 2 is 3.437?Å.     

An ab initio quantum chemical study of reaction mechanisms in the C2H2/CH3OH/KOH/DMSO system

An ab initio quantum chemical study (MP2/6-311++G**//B3LYP/6-31+G*) of a number of possible interactions is performed for the gas phase system of acetylene—potassium hydroxide-dimethylsulfoxide(DMSO)—methanol and with regard to the solvent effect within the continuum model. Key structures in the vinylation reaction are shown to be methoxide ion complexes with the alkali metal hydroxide and acetylene molecules. The formation of these complexes results in the activation of the acetylene molecule and an increase in the nucleophilicity of the methoxide ion. In the C₂H₂/CH₃OH/KOH/DMSO reaction system, a proton exchange between the acetylene molecule and the anionic nucleophile ([OH]^- and [CH₃O]^-) is freely performed with the formation of systems with ethynideions, whereas the thermodynamically preferable formation of vinyl alcohol or methyl vinyl ether is determined by a barrier of 20 kcal/mol.     

The Design of Ion Selective Macrocycles and the Solid-Phase Extraction of Ions Using Molecular Recognition Technology: A Synopsis

Abstract

We have combined organic synthesis and the study of cation complexation properties of the crown ethers in an effort to design and prepare macrocyclic ligands that will selectively bind specific cations.^1–3 The bis-phenol-containing diazacrown ethers allow a great number of possibilities for designing ion selectivity into macro-cyclic ligands. In these cases, the macrocyclic ligand can be varied as can the type and position of attachment of the phenolic group. Any of these variations can have profound effects on complexation properties. For example, ligand 1 (see Figure 1), where two 5-chloro-8-hydroxy-quinoline (CHQ) groups are attached through their positions 7, is selective for Mg²⁺ over other alkali and alkaline earth metal ions (see Table I).⁴ On the other hand, ligand 2, where the two CHQ groups are attached through their positions 2, exhibits remarkable selectivity for K⁺ and Ba²⁺ over all other metal ions studied. The chemical shifts of the CHQ protons in the ¹H NMR spectra of K⁺- and Ba²⁺- complexes with 2 shift significantly upfield in relation to the free ligand. These shifts are indicative of an overlap of the two CHQ substituents. Indeed, the crystal structure of the Ba²⁺-2 complex shows that Ba²⁺ is in the center of a pseudo-cryptand with the diazacrown forming two arms and the two overlapping CHQ groups forming the third.^4,5 This pseudo-cryptand formation accounts for the fact that the K⁺-2 and Ba²⁺-2 complexes are so stable in comparison to complexes of 2 with the other alkali and alkaline earth cations.