Ethylenediaminetetraacetate Ion Research Articles

Enhancing the light absorption and dielectric properties of nitrate intercalated Zn-Al Layered double hydroxide through anionic exchange with ethylenediaminetetraacetate

Herein, we have reported a comparative study of two Zn-Al Layered double hydroxides (LDH) intercalated by nitrate (NO3−) and ethylenediaminetetraacetate (EDTA) ions, respectively. Indeed, nitrate-intercalated LDH was prepared by the coprecipitation method at a constant pH with Zn/Al = 2 (molar ratio), and used as a precursor for the synthesis of EDTA intercalated LDH through the anionic exchange method. Subsequently, these two LDH were analyzed by inductively coupled plasma, characterized by X–ray diffraction, thermogravimetric analysis and three spectroscopic techniques: Fourier transform infrared spectroscopy, diffuse reflectance spectroscopy and impedance spectroscopy. The exchange of nitrate ions by EDTA led to a decrease in the electrical conductivity, dielectric constant and dielectric loss tangent, and revealed an important increase in the absorption coefficient in UV–Vis–NIR range, with a large gap energy of approximately 6.30 eV. This work demonstrates the advantage of EDTA ions in decreasing the dielectric dissipation energy, and improving the light absorption of LDH compound.

Iron(III) Complexation with Barbituric and 2-Thiobarbituric Acids in Aqueous Solution

Complexation in systems containing iron(III) chloride and barbituric (H2BA) or 2-thiobarbituric (H2TBA) acid has been studied by spectrophotometry and pH-metry in the pH range of 1.3–3.3 (I = 0.1 (NaCl), t = 20°C). The presence of 1 : 1 complexes with mono- and deprotonated forms of the ligand has been established, and their stability constants (in log units) have been determined: 1[FeHBA]2+ (3.49 ± 0.15), [FeHTBA]2+ (2.69 ± 0.07), [FeBA]+ (12.22 ± 0.13), and [FeTBA]+ (11.05 ± 0.08). It has been shown that the higher thermodynamic stability of barbiturate complexes compared to 2-thiobarbiturate ones is due to the greater basicity of the barbiturate anion. Based on the stability constants obtained, it has been proposed to use orthophosphate, fluoride, and ethylenediaminetetraacetate ions to eliminate the interfering effect of iron(III) in the determination of malondialdehyde by the thiobarbiturate method. Orthophosphoric acid is the most convenient for practical applications, as it makes it possible to mask iron(III) and to create a strongly acidic medium necessary for the formation of a colored malondialdehyde–H2TBA adduct.

Dicopper(II)-EDTA Chelate as a Bicephalic Receptor Model for a Synthetic Adenine Nucleoside.

In the extensive field of metal ions, their interactions with nucleic acids, and their constituents, the main aim of this work is to develop a metal chelate suitable to recognize two molecules of an adenine nucleoside. For this purpose, the dinuclear chelate Cu2 (µ-EDTA) (ethylenediaminetetraacetate(4-) ion (EDTA)) is chosen as a bicephalic receptor model for N9-(2-hydroxyethyl)adenine (9heade). A one-pot synthesis is reported to obtain the compound [Cu2(µ2-EDTA)(9heade)2(H2O)4]·3H2O, which has been characterized by single-crystal X-ray diffraction and various spectral, thermal, and magnetic methods. The complex unit is a centro-symmetric molecule, where each Cu (II) center is chelated by a half-EDTA, and is further surrounded by an N7-dentate 9heade nucleoside and two non-equivalent trans-O-aqua molecules. The metal chelate-nucleoside molecular recognition is referred to as an efficient cooperation between the Cu-N7(9heade) coordination bond and a (9heade)N6-H···O(carboxyl, EDTA) interligand interaction. Theoretical calculations are also made to account for the relevance of this interaction. The extreme weakness with which each water molecule binds to the metal center disturbs the thermal stability and the infrared (FT-IR) and electron spin resonance (ESR) spectra of the compound.

Carbonate Form of Mg,Al-Layered Double Hydroxides for Concentrating Eu(III) and Its Subsequent Analytical Determination in Natural Aqueous Media

The efficiency of the sorption of Eu(III) by various forms of Mg,Al- and Zn,Al-layered double hydroxides (LDH) from model and natural waters at various pH was estimated for concentrating this metal ions and its subsequent spectrophotometric determination. It was found that the almost complete extraction of Eu(III) is reached on the carbonate form of Mg,Al-LDH by a deposition mechanism because of the formation of poorly soluble compounds of this element (carbonate and hydroxide of Eu(III) at pH ≥ 6.2, which correlates with the calculated Eu(III) speciation in aqueous solution in the presence of carbonate ions. The distribution coefficients of Eu(III) are 1.4 × 106 cm3/g (the pH of the initial solution is ≥7.0; the pH of the solution after the sorption is ≥ 6.87), which is indicative of a high efficiency of this sorbent with respect to this metal ion. For Mg,Al- and Zn,Al-LDH intercalated with organic complex-forming ligands—citrate and ethylenediaminetetraacetate ions, the dominant mechanism Eu(III) extraction from aqueous media is the complex formation. The distribution coefficients of Eu(III) on these sorbents are (0.26—22.71) × 103 cm3/g. For concentrating Eu(III) and its spectrophotometric determination in natural waters, it was proposed to use the carbonate form of Mg,Al-LDH with its subsequent decomposition by a nitric acid solution after the sorption. It was shown that the major components of natural waters and the constituents of this sorption materials do not affect the correctness and accuracy of the determination of Eu(III) by this method with arsenazo III (at pH 2.6 ± 0.1). The linearity range of the calibration graph is 1–50 μg Eu(III) in 50 cm3 of the final solution cm3 (λ = 650 nm). The proposed method of concentrating and determining Eu(III) was tested on samples of model, tap, and surface waters (the sorbent weight is 0.100 g, and the water sample volume is 500 cm3).

Extraction of Organic Compounds from Aqueous Solutions by the Nanofiltration Method

Extraction from aqueous solutions of oxalate and ethylenediaminetetraacetate (EDTA) ions, anionic (ASF) and nonionogenic (NSF) surfactants, and a complex of Co(III) with EDTA by the nanofiltration (NF) method was studied. It was shown that 98–99% of NSFs and EDTA, 85–90% of ASFs and oxalate ions, and 76–79% of the Co(III)–EDTA complex can be extracted with the use of a polymeric NF membrane. The possibility is demonstrated of effectively extracting EDTA and oxalate ions with an NF membrane at solution pH varied within the range 1–13 and sodium nitrate concentrations of 0 to 159 g/dm3. A conclusion is made that using the nanofiltration method is promising for effective removal of various organic complexing and surface-active substances and the Co(III)–EDTA complex from solutions with complex salt composition.

Characterization and application of alkali-soluble polysaccharide of Carica papaya seeds for removal of indigo carmine and Congo red dyes from single and binary solutions

Adsorption of Congo red (CR) and indigo carmine (IC) dyes by alkali-soluble polysaccharide (ASP) extracted from Carica papaya seeds was studied in single as well as in binary mixtures. The adsorption study was performed by varying operating variables such as pH, initial dye concentration, adsorbent dosage, contact time and temperature. Fourier-transform infrared, X-ray diffraction, elemental analysis and scanning electron microscopy images were used for characterization of ASP and dye-loaded ASP. Kinetic results fitted well the pseudo-second order and Elovich models. The Langmuir-Freundlich isotherm shows the best fit to the experimental data of both L-shape in single component whereas, the partial competitive Langmuir isotherm gives a best adjustment of binary experimental data. The maximum adsorption capacities of CR and IC in single/binary mixtures at 30 °C were 319.08/635.99 mg/g and 168.51/102.65 mg/g respectively. The thermodynamic study showed that the adsorption process is thermodynamically favorable, spontaneous, with exothermic process for IC and endothermic one for CR. The adsorption mechanism behaviors were dominated by the electrostatic interactions between adsorbent surface functional groups and dyes molecules. The desorption study showed that ethylenediaminetetraacetate ion (EDTA) was the best eluant for both dyes recovery. A good removal efficiency obtained during the five executed cycles suggests a good reusability of ASP.

Removal of radionuclides, macrocomponent metal ions, and organic compounds from solutions by nanofiltration

Removal of Mg2+, Сa2+, Cu2+, Ni2+, Zn2+, Fe3+, and Pr3+ ions, tracer amounts of 137Cs, 85Sr, and 60Co radionuclides, and oxalate and ethylenediaminetetraacetate ions from solutions using a polymeric nanofiltration (NF) membrane produced by RM Nanotekh (Russia) was studied. The selectivity (S) of the NF membrane to multicharged metal cations is considerably higher than to single-charged cations. The NF membrane exhibits the highest selectivity (S = 94–97%) to triple-charged Fe3+ and Pr3+ ions and double-charged Cu2+ ions. The selectivity to double-charged Mg2+ and Zn2+ ions is somewhat lower (90–94% on the average). Among doublecharged cations, the NF membrane exhibits the lowest selectivity (80–88%) to Ni2+ and Cа2+ ions. The NF membrane shows high performance in retention of tracer amounts of Sr (S = 95%) and Co (S > 99%) radionuclides, and also of oxalate (S = 94.5%) and ethylenediaminetetraacetate (S = 97.5%) ions. Examples of using the nanofiltration method for removing 60Co from a model solution simulating NPP bottom residue and for removing transition metal impurities from a LiCl solution are presented.

Single and simultaneous sorption of copper ions and p-cresol into surfactant-modified hydrotalcite-like compound with chelating ligand

In this study, the simultaneous sorption of Cu2+ and p-cresol, which are frequently encountered together in waste waters, into Mg–Al hydrotalcite-like compound (HTlc) modified with dodecylsulfate and ethylenediaminetetraacetate ions (SDS–EDTA-HTlc) was described and compared to a single adsorbate situation. Modification can decrease the specific surface area of the Mg–Al HTlc but promote the sorption for Cu2+ and p-cresol, respectively. Pseudo-second order equations were fitted to the kinetic data, and the rate constants were evaluated. The effect of pH on the simultaneous sorption efficiency was also studied. Freundlich isotherm model was used to analyze the equilibrium data for each adsorbate in both single and binary systems. In binary mixtures, competition for binding sites was identified. The equilibrium Cu2+ uptake decreased with an increased initial p-cresol concentration, whereas the existence of Cu2+ in the solution enhanced the p-cresol removal.

Chemolysis of calcium oxalate stones: study in vitro and possible clinical application

The flow cell modeling clinical conditions have been used to study the interaction between dilute chemolytic solutions and large calcium oxalate renal stones. The stone treatment with 5% disodium ethylenediaminetetraacetate aqueous solutions or citrate buffer are found not to provide notable disruption of the samples studied. The significant improvement is reached with the mixed compositions containing both natural and synthetic chelating reagents:citrate and ethylenediaminetetraacetate ions as well as an antibiotic. Description of the chemolytic irrigation, numerical results and their possible clinical application are the main topic of the present research.

Cobalt(II) cation extraction from solutions containing ethylenediaminetetraacetate and oxalate ions

A new approach to extracting cobalt(II) from non-borate and borate solutions of liquid radioactive wastes containing ligands of ethylenediaminetetraacetate and oxalic acid is proposed. The approach is based on the difference in the stability of complexes of organic ions with metals. Substituting iron(III) for cobalt results in almost complete liberation of Co2+ from the complex. Coprecipitation of Co2+ with Fe3+ in the form of oxohydroxides results in the liberation of Co2+ from solution into the solid phase. An excess of Fe3+ cations with respect to Co2+ and an increase of acidity, processing temperature, and aging time of the solutions at the preliminary stage results in complete liberation of cobalt from the solution for pH ≥ 12.

Syntheses, Characterization and Structural Determination of Nine Coordinated N2H5[Ce(edta)(H2O)3]·4H2O and N2H5[Eu(edta)(H2O)3]·4H2O

Hydrazinium complexes of Ce(III) and Eu(III) ethylenediaminetetra-acetate hydrates have been synthesized in aqueous solution and characterized by hydrazine and metal analyses, elemental analysis, infrared spectra, X-ray power diffraction and single crystal X-ray diffraction techniques. The CeIIIN2O7 parts in the complex anion has a pseudomono-capped square antiprismatic nine-coordinate structure, in which the six coordinated atoms (two N and four O) from the ethylenediaminetetraacetate ion and three water molecules are coordinated to the central rare earth metal ion directly. The EuIIIN2O7 part in the complex anion has the same structure as CeIIIN2O7 part. The crystal of the cerium complex belongs to the orthorhombic crystal system and Fdd2 space group. The crystal data are the follows: a = 19.7281(7) A, b = 35.7790(11) A, c = 12.3244(4) A, α = β =γ = 90°, V = 8699.2(5) A3. The final R and Rw are 0.020 and 0.0589 for with I > 2σ (I) and 3,842 reflections, respectively. The crystal of the europium complex is isostructural with the cerium complex. The crystal data of europium complex are: a = 19.7281(7) A, b = 35.7790(11) A, c = 12.3244(4) A, α = β =γ = 90°, V = 8699.2(5) A3. The final R and Rw are 0.0252 and 0.687 for with I > 2σ (I) and 3,842 reflections, respectively. The X-ray powder diffraction patterns and infrared spectra of the complex are super imposable indicating their structural similarity. Hydrazinium complexes of cerium(III) and europium(III) ethylenediaminetetraacetate hydrates have been synthesized and characterized by analytical, spectral, thermal and X-ray studies. The crystal structures of both the complexes have been described.

The enthalpies of interactions of Ca2+(aq) and C2O 4 2− (aq) ions in complexon solutions: Competition between complexation and precipitation

The thermal effects of mixing of aqueous calcium chloride with sodium citrate and ethylenedi-aminetetraacetate in the absence and presence of sodium oxalate have been measured at 25°C. The thermal effects of dilution of aqueous calcium chloride solutions were determined. The thermal effects of calcium oxalate precipitation and formation of calcium complexes with citrate and ethylenediaminetetraacetate ions were calculated. The 1% solution of sodium citrate inhibited the formation of CaC2O4 (s); in a 1% solution of sodium ethylenediaminetetraacetate with [Ca2+][C2O 4 2− ] > 10−5, the endothermal formation of the [CaEdta]2− complex quickly changed to exothermal precipitation. The 3 and 5% solutions of complexons showed a pronounced inhibiting effect on the formation of urinary stones even when the concentration of calcium and oxalate ions in solution exceeded the product of solubility of CaC2O4 by four and more orders of magnitude.

Diammonium aqua(ethylenediaminetetraacetato)iron(II) trihydrate

In the title compound, (NH4)2[Fe(C10H12N2O8)(H2O)]·3H2O, the FeII center is in a distorted penta­gonal-bipyramidal geometry. Two carboxyl­ate O and two N atoms from the ethyl­enediaminetetra­acetate (EDTA) ion and one O atom from coordinated water comprise the equatorial plane. Two other carboxyl­ate O atoms from the EDTA ion occupy the apical sites. Both ammonium cations and all water mol­ecules function as hydrogen-bond donors, and ten N—H⋯O and nine O—H⋯O hydrogen bonds form a three-dimensional network between the complex anions, cations and the water mol­ecules.

The heterometallic two-dimensional structure in the Ba2[Cu(L)](ClO4)2 · nH2O crystals (L = ethylenediaminetetraacetate, n = 6; L = ethylenediaminetetra-3-propionate, n = 5)

The crystals of Ba2[Cu(Edtp)](ClO4)2 · 5H2O (i) contain the tetragonal-pyramidal complexes of Cu(II) with ethylenediaminetetra-3-propionate ion with one noncoordinated propionate group. The [Cu(Edtp)]2− complex ions and two sorts of the Ba atoms form two-dimensional supramolecular aggregate. Two Ba(1) atoms and one Cu atom form a tetramer by means of the coordinated carboxyl group and a free propionate group. The tetramers are united through the propionate group into ribbons, which are joined by the Ba(2) atoms into the layers. The coordination sphere of each B atom involves four water molecules, including two bridging water molecules. The perchlorate ions are also coordinated by the Ba atoms, one Ba atom acting as a bridge. The structure of the previously studied Ba2[Cu(Edta)](ClO4)2 · 6H2O (II) crystals with the hexadentate ethylenediaminetetraacetate ion is shown to be similar to that of complex I, but in the case of II, the Ba atoms are equivalent as regards the number of the complex anions bound to them.

Crystal structures of strontium and barium ethylenediaminetetraacetato cobaltates(III), Sr[CoEdta]2·9H2O and Ba[CoEdta]2·8H2O: Comparison of the structures of complexes in the series M’[CoEdta]2·nH2O (M’ = Mg, Ca, Sr, Ba; n = 7–10)

Cobalt(III) complexes, namely, Sr[CoEdta]2·9H2O (I) and Ba[CoEdta]2·8H2O (II) (where Edta4- is the ethylenediaminetetraacetate ion), are synthesized. The crystal structures of these compounds are determined using X-ray diffraction. Crystals of compound I are triclinic, a = 6.514(1) A, b = 11.410(2) A, c = 12.317(2) A, α = 67.87(1)°, β = 88.73(2)°, γ = 84.22(2)°, V = 843.63(3) A3, Z = 1, space group P1, and R = 0.0295 for 4130 reflections with I > 2σ(I). Crystals of compound II are monoclinic, a = 6.543(2) A, b = 12.895(3) A, c = 19.489(4) A, β = 95.24(3)°, V = 1637.5(5) A3, Z = 2, space group P21, and R = 0.050 for 3016 reflections with |F| > 3σ(|F|). The structures of compounds I and II are compared with those of the previously studied complexes Mg[CoEdta]2·10H2O (III) and Ca[CoEdta]2·7H2O (IV). The crystal structure of the cobalt(III) complex with the strontium cation (I) is topologically similar to the crystal structure of cobalt(III) complex with the calcium cation (IV). The former structure is built up of the two symmetrically independent homochiral anionic complexes [CoEdta]− (AI and BI), the aqua cations [Sr(H2O)8]2+, and the molecules of crystalization water wcr. The structure of compound II involves two independent anions [CoEdta]− (AII and BII) with different chiralities (i.e., they are kryptoracemates). The AII anions are linked via the barium cations into {Ba(H2O)7[CoEdta]}1∞+ chain agglomerates due to the incorporation of two terminal oxygen atoms Ou of the anions neighboring in the chain into the coordination sphere of the barium atom. All four structures (I–IV) contain stacks composed of the [CoEdta]− homochiral anions forming layers aligned parallel to the (001) plane. The aqua cations [Sr(H2O)8]2+, [Mg(H2O)6]2+, and [Ca(H2O)7]2+ or the partially hydrated barium cations [Ba(H2O)7(Ou)2]2+ (in structure II), as well as water molecules wcr, are located between the anion layers. The octahedral environment of the cobalt(III) atoms consists of donor atoms (2N and 4O) of the Edta4− ligand. The Co-N bonds in the AI, BI, AII, and BII anions [the mean bond lengths are 1.927(4), 1.921(4), 1.910(6), and 1.921(6) A, respectively] are considerably longer than the Co-O bonds [the mean bond lengths are 1.908(5), 1.902(5), 1.904(6), and 1.908(6) A, respectively]. The mean distances Sr-Ow and Ba-Ow in the strontium and barium polyhedra are 2.609(4) and 2.834(8) A, respectively. The mean distance Ba-Ou is 2.814(7) A.

Highly selective crystallization of metal(II) ions with 1,3-pdta ligand: Syntheses and crystal structures of the [Mg(H2O)6][Cd(1,3-pdta)(H2O)]·2H2O and two isomorphic [Zn(1,3-pdta)]2− complexes

X-ray crystallography has been applied to investigate 1,3-pdta complexes of Zn 2+ and Cd 2+ ions. The [Zn(1,3-pdta)] 2− ( a ) and [Cd(1,3-pdta)(H 2 O)] 2− ( b ) complexes are different in coordination number and geometry, as ( b ) constitutes the first example of transition metal complex with 1,3-pdta ligand that possesses CN equal to 7. Three new hexadentate complexes: [Mg(H 2 O) 6 ][Zn(1,3-pdta)] · 2H 2 O ( 1 ), [Zn(H 2 O) 6 ][Zn(1,3-pdta)] · 2H 2 O ( 2 ) and [Mg(H 2 O) 6 ][Cd(1,3-pdta)(H 2 O)] · 2H 2 O ( 3 ) (where 1,3-pdta represents the 1,3-propanediaminetetraacetate ion) have been synthesized and characterized. The structures of 1 , 2 and 3 have been determined by X-ray crystallography. The complexes 1 and 2 crystallize in the space group Pnna of the orthorhombic crystal system and their crystals are isomorphic with those of other 1,3-pdta complexes containing metal(II) ions of the ionic radii of about 0.8–0.9 Å. The complex 3 crystallizes in the space group Pbcn of the orthorhombic crystal system and its crystals are isomorphic with those of [Mg(H 2 O) 6 ][Mn(edta)(H 2 O)] · 2H 2 O (where edta is the ethylenediaminetetraacetate ion). The structural units of 1 and 2 consist of discrete [Zn(1,3-pdta)] 2− and [M II (H 2 O) 6 ] 2+ (M(II) = Mg ( 1 ) or Zn ( 2 )) octahedra, and two water solvent molecules all of which lie on a twofold axis of symmetry. The structural unit of 3 consists of discrete complex ions: [Cd(1,3-pdta)(H 2 O)] 2− and [Mg(H 2 O) 6 ] 2+ which are situated on twofold axis of symmetry and inversion centre, respectively, and two symmetry related water solvent molecules. The coordination polyhedron formed around Cd(II) is distorted pentagonal bipyramid. In contrast to crystals 1 and 2 in which the complex cations and anions alternate, each being octahedrally surrounded by the counter ions, a layered arrangement of cationic and anionic species is observed in 3 .

New copper(II) compound having protonated forms of ethylenediaminetetraacetate(4−) ion (EDTA) and adenine (AdeH): synthesis, crystal structure, molecular recognition and physical properties of (AdeH 2)[Cu(HEDTA)(H 2O)]·2H 2O

The stoichiometric reaction of Cu 2CO 3(OH) 2, ethylenediaminetetraacetic acid (H 4EDTA=C 2H 4(N(CH 2CO 2H) 2) 2) and adenine (AdeH) in water yields crystalline samples of adeninium aqua-(ethylenediamine- N, N, N′-triacetato-N′-acetic)copper(II) dihydrate. The compound (AdeH 2)[Cu(HEDTA)(H 2O)]·2H 2O was studied by TG analysis (with FT-IR study of the evolved gasses), IR, electronic and ESR spectra, magnetic susceptibility data, and single crystal X-ray diffraction methods (monoclinic system, space group P2 1/ c ( a=7.053(1), b=42.540(5), c=7.798(1) Å, β=104.24(1)°, Z=4, and final R 1=0.042 for 5113 independent reflections). The asymmetric unit consists of a salt of adeninium(1+) and the aqua-copper(II) complex of HEDTA 3− as chelating agent, and two crystallisation water molecules. The Cu(II) atom exhibits an elongated octahedral coordination (type 4+1+1). The pentadentate HEDTA 3− ligand has a typical E,G/R configuration and a free N-carboxymethyl arm. The uncoordinated AdeH 2 + ion recognises the anion [Cu(HEDTA)(H 2O)] − through two rather linear NH⋯O hydrogen bonds involving the protonated N1 heterocyclic atom and one H atom of the exocyclic-N6 amino group with two O atoms of the same HEDTA 3− carboxylate group (173(3) or 175(3)°, and 2.64(1) or 2.80(1) Å, respectively). This ion pair recognises itself by a π,π-stacking between the six-membered aromatic rings of adjacent AdeH 2 + ions which lay out slightly slipped ( β= γ=10.1°) and anti-parallel at 3.34 Å, thus forming aggregates {(AdeH 2)[Cu(HEDTA)(H 2O)]} 2. The remaining OH (carboxy or water) and NH (heterocyclic or exocyclic) polar bonds interact with O carboxylate or water atoms or N3 and N7 adeninium atoms building the crystal in an extensive 3D-hydrogen bonded network.

Synthesis and Study of Heterometallic Co–Bi Compounds Based on Ethylenediaminetetraacetic Acid. Crystal and Molecular Structures of [Co(DH)2(o-NH2C6H4CH3)2]2[Bi2(μ-Edta)2(H2O)2] · 10H2O (DH2 is dimethylglyoxime)

Compounds of the [Co(DH)2A2](BiEdta) · 6H2O type (where DH is the monodeprotonated dimethylglyoxime –ON=C(CH3)–(CH3)C=NOH; A is the o-, m-, or p-toluidine; and Edta is the ethylenediaminetetraacetate(4–) ion) were synthesized and studied. The composition and structures of the complexes were determined from their UV and 1H NMR spectra and from X-ray diffraction data. The isomer [Co(DH)2(o-NH2C6H4CH3)2]2[Bi2(μ-Edta)2(H2O)2] · 10H2O was structurally characterized using X-ray diffraction analysis. The crystals are triclinic: a = 12.153(2) A, b = 12.824(3) A, c = 16.215(3) A, α = 67.73(3)°, β = 86.18(3)°, γ = 66.96(3)°, space group P\(\overline 1\), ρ(calcd) = 1.719 g/cm3, Z = 4. The structure is composed of complex binuclear [Bi2(μ-Edta)2(H2O)2]2– anions, [Co(DH)2(o-NH2C6H4CH3)2]+ cations, and molecules of crystallization water. The Edta4– anion chelates with the Bi atom in a hexadentate manner (N2O4); the fifth O atom functions as a bridging ligand. The bismuth coordination polyhedron can be regarded as a strongly distorted antiprism. In the octahedral cation, the Co(III) atom coordinates four N atoms of two DH ligands (average Co–N 1.897 A) and two N atoms of two o-toluidine molecules (Co–N 2.023 A). Thermolysis of the complexes studied was found to proceed in several successive steps, namely, the deaquation, deamination, and pyrolysis of the ligands.

Crystal structure of strontium aqua(ethylenediaminetetraacetato)cobaltate(II) tetrahydrate Sr[CoEdta(H2O)] · 4H2O

The complex Sr[CoII Edta] · 5H2O (I) (where Edta 4− is the ethylenediaminetetraacetate ion) has been synthesized. The crystal structure of this compound is determined by X-ray diffraction. Crystals are monoclinic, a = 7.906(2) A, b = 12.768(2) A, c = 18.254(3) A, β = 95.30(3)°, V = 1834.8 A3, space group P21/n, Z = 4, and R = 0.036. The structure is built up of the binuclear complex fragments {Sr(H2O)3[CoEdta(H2O)]}, which consist of the anionic [CoEdta(H2O)]2− and cationic [Sr(H2O)3]2+ units linked by the Sr-O bonds into a three-dimensional framework. The coordination polyhedra of the Co and Sr atoms are mono-and bicapped trigonal prisms. The coordination sphere of the Co atom (the coordination number is equal to 6 + 1) involves six donor atoms (2N and 4O) of the Edta 4− ligand and the Ow atom of water molecule. One of the Co-O distances (2.718 A) is considerably longer than the other Co-Olig distances (2.092–2.190 A) and the Co-Ow(1) distance (2.079 A). The Sr coordination polyhedron (the coordination number is eight) contains three water molecules, three carbonyl O atoms of the three different anionic complexes, and two O atoms of one acetate group of the fourth anionic complex. The Sr-O distances fall in the range 2.535–2.674 A. The structural formula of the compound is {Sr(H2O)3[CoEdta(H2O)]}3∞ · H2O.

Determining the EDTA Content in a Consumer Shower Cleaner. An Introductory Chemistry Laboratory Experiment

At Altoona College, Chemistry 11 is offered to students as a preparatory course for the University's Chemical Principles course, Chem 12. A relevant laboratory is a source of motivation for the students to learn the chemistry. One way of making the laboratory relevant is to analyze the chemical components of consumer products. Several new shower-cleaning products have been introduced, which advertise that cleaning the shower is no longer necessary. The cleaners work using a combination of surfactants, alcohols, and a chelating agent. The Web site of a popular shower cleaner lists EDTA (ethylenediamine tetraacetate ion) as the chelating agent. The classic EDTA/calcium complexometric titration can be used to determine the EDTA content of the cleaner. This article describes the experiment to determine the EDTA content in a shower-cleaning product.