Colorless Needles Research Articles

Diprotonation of taurine: 2-[dihydroxy(oxo)sulfanyliumyl]ethanaminium bis[hexafluoroarsenate(V)

Taurine is part of the cysteine cycle and is one of the few naturally occuring organosulfur-based molecules in the human body. As implied by modern studies, protonated taurine is of biological impact. The first attempts to isolate its protonated species in the binary superacidic system HF/SbF5 were performed by Hopfinger, resulting in the isolation of monoprotonated taurine. Since the chosen conditions seemed rather harsh, investigations in less acidic systems were performed at room temperature to explore the involved protonated species. Herein, we present the structure of 2-[dihydroxy(oxo)sulfanyliumyl]ethanaminium bis[hexafluoridoarsenate(V)], [H2O3SC2H4NH3][AsF6]2, the diprotonated form of 2-aminoethanesulfonic acid (taurine). It was synthesized in the binary superacidic system HF/AsF5 and crystallizes as colourless needles. Diprotonated taurine was structurally characterized by single-crystal X-ray diffraction analysis, low-temperature vibrational spectroscopy and NMR spectroscopy.

Rerefinement of the crystal structure of BiF5.

The crystal structure of bis-muth penta-fluoride, BiF5, was rerefined from single-crystal data. BiF5 crystallizes in the α-UF5 structure type in the form of colorless needles. In comparison with the previously reported crystal-structure model [Hebecker (1971 ▸). Z. Anorg. Allg. Chem. 384, 111-114], the lattice parameters and fractional atomic coordinates were determined to much higher precision and all atoms were refined anisotropically, leading to a significantly improved structure model. The Bi atom (site symmetry 4/m..) is surrounded by six F atoms in a distorted octa-hedral coordination environment. The [BiF6] octa-hedra are corner-linked to form infinite straight chains extending parallel to [001]. Density functional theory (DFT) calculations at the PBE0/TZVP level of theory were performed on the crystal structure of BiF5 to calculate its IR and Raman spectra. These are compared with experimental data.

Structure Prediction and Ultrasonic Assisted Synthesis of Coordination Compound Cadmium (II) Bromide with N,N’-diethylthiourea Ligand

Cadmium (II) halides with N,N'-diethylthiourea (detu) ligands at a stoichiometry of 1: 2 tend to form molecular complexes [Cd(detu)2X2] with a distorted tetrahedral geometry at the central atom. Generally, these complex compounds are prepared by the conventional method of reflux for 4 hour. The use of ultrasonic waves for complex synthesis can be an alternative to make the reaction time more efficient and environmentally friendly. The aim of this study was to synthesize and characterize complex compounds from CdBr2 and detu ligands using the ultrasonication method that have not previously reported. The synthesis of complex compounds was carried out by reacting CdBr2 and detu (1:2) in methanol solvent. In the synthesized compounds, a melting point test, electrical conductivity test, Fourier Transform Infrared (FTIR), Scanning Electron Microscope-Energy Dispersive Xray (SEM-EDX), qualitative test of bromide ion and calculation of free energy using Spartan'14 software were carried out for the complex structure prediction. The complex compound resulted has colorless needle crystals with a melting point of 93-94°C. The results of the EDX analysis provide the empirical formula C10H24CdBr2N4S2. The electrical conductivity test data and the bromide ion qualitative test proved that the synthesized complex compound was a molecular complex compound with the molecular formula [Cd(detu)2Br2]. The complex compound has two possible structures, namely a distorted tetrahedral and a square planar. Free energy calculations showed that complex compounds with a distorted tetrahedral structure and a square planar have free energies of -527.5574 kJ/mol and -408.7424 kJ/mol, respectively.

Zinc(II) vs cadmium(II) in organic chelate-free chemistry: Synthesis and characterization of 1-D [Zn2(N3)4(MeCN)3]n and 2-D [Cd3(N3)6(MeCN)2]n coordination polymers

The employment of a relatively unexplored reagent, namely the Me3SiN3, in the coordination chemistry of Zn(II) and Cd(II), in the absence of any external organic chelating/bridging ligand, has led to two new, azido-bridged coordination polymers with formulae [Zn2(N3)4(MeCN)3]n (1) and [Cd3(N3)6(MeCN)2]n (2), respectively. The reaction between Zn(ClO4)2·6H2O, Me3SiN3 and NEt3 in an 1:8:2 molar ratio afforded colorless needle-like crystals of the 1-D chain 1, whereas the exact same reaction but with Cd(ClO4)2·6H2O in place of the ZnII starting material resulted in the formation of colorless needles of the 2-D polymer 2. The repeating unit of 1 consists of a [Zn4(N3)8(MeCN)6] cluster with a defective dicubane core; the vertices of the latter are occupied by the four metal ions and the bridging ligation is provided by two μ3-1,1,1 (or 3.30) and six μ-1,1 (or 2.20) end-on N3− groups. In contrast, compound 2 comprises a central [Cd4(μ3-N3)4(MeCN)4]4+ cubane-like unit, unprecedented in the coordination chemistry of CdII, which is linked to [Cd(N3)4]2− tetrahedra through μ-1,1 end-on N3− groups, eventually forming the overall layered structure of 2. Topological analysis of 2 shows a trinodal (3,4,5) network with stoichiometry (3-c)2(4-c)(5-c)2 and a very rare topological type of 3,4,5L6. Terminal ligation in both 1 and 2 is solely provided by MeCN solvate molecules. Despite the optical inactivity of complex 1, the 2-D polymer 2 exhibits an intense violet-to-blue emission upon excitation at 225 or 277 nm in the solid-state, which is tentatively ascribed to an intra-ligand fluorescence from the coordinated azido groups within the robust 2-D network. Although it is strongly evidenced that the chemistry of ZnII and CdII follows the same general trends, and thus the majority of these coordination compounds are isomorphous, the present study demonstrates the formation of two chemically, structurally and optically different compounds of divalent Group 12 metal ions, under the exact same experimental conditions. This work may pave the way to further study the chemical, structural and physicochemical properties of organic chelate-free coordination polymers and clusters using different Me3SiX (X = OCN−, SCN−, CN− and RCO2−) reagents.

Isolation of lupenone (18-Lupen-3-one) from Roscoea purpurea root extract

Background: Endangered plant “Kakoli” is important component of Ashtwarga group of plants and anti-aging Ayurvedic preparations. Due to limited supply of original plant, official substitutes and common adulterants are being used by drug manufacturers. There is a need to identify a marker compound that could differentiate original plant from substitutes and common adulterants.
 Objective: To isolate and characterize the marker compound from roots of this plant.
 Material and methods: The extract of plant root was prepared in methanol and marker compound was isolated from methanol extract through column chromatography by using silica gel (60–120 mesh size) in glass column (1000mm x 50mm). The compound was obtained in fractions numbered 990-1550 and isolated by cutting and pooling of TLC plate of compound having Rf = 0.52 by the use of mobile phase toluene: ethyl acetate: formic acid (9.5: 0.5: 0.1 v/v/v). Compound was characterized by using IR, NMR, Mass and UV spectroscopy.
 Results: The methanol extract was blackish brown in color and showed the presence of alkaloids, terpenoids, phytosterols, flavonoids, phenolics and amino acid. The isolated compound was found to be colorless terpenoid needle with m.p. 168-171°C; [α]D +62.8° (c 1.0,CHCl3). Spectral analysis confirmed presence of lupenone.
 Conclusion: In present study lupenone was isolated for the first time from Kakoli. None of adulterants and substitutes of Kakoli are reported to have lupenone hence can be used as marker for identification as well as differentiation of the plant from official substitutes and common adulterants.
 Bangladesh Journal of Medical Science Vol.19(4) 2020 p.692-696

Crystal Structure and Properties of Iridium(I)(1,5-Cyclooctadiene) (η5-Tetramethylcyclopentadiene) [Ir(cod)CpMe4

Volatile iridium complex [Ir(cod)CpMe4] (CpMe4 is tetramettiylcyclopentadienyl, cod is 1,5-cyclooctadiene) is synthesized and characterized by IR and NMR spectroscopy methods. The complex is a solid phase under standard conditions and crystallizes in the form of colorless needle shaped crystals. The structure of [Ir(cod)CpMe4] is solved by X-ray diffraction: chemical formula IrC17H25, space group P-1, a = 6.4631(3) A, b = 8.4620(4) A, c = 13.5577(8) A, α = 85.770(2)°, β = 84.611(2)°, γ = 78.013(2)°, V = 720.99(6) A3, Z = 2, dcalc = 1.942 g/cm3, μ = 9.240 mm−1. Tetramethylcyclopentadienyl is a η5-coordinated ligand, 1,5-cyclooctadiene is a η4-coordinated ligand in the cis-cis conformation. According to the thermogravimetric data, the complex transfers to the gas phase congruently upon heating.

Pharmacokinetics, tissue distribution, and safety evaluation of a ligustilide derivative (LIGc)

Ligustilide (LIG) is the main active ingredient of Angelica sinensis (Oliv.) Diels and has a neuroprotective effect against ischemic stroke. However, owing to its multi-conjugated unstable structure, the compound has poor drug-forming properties. Therefore, we synthesized highly stable colorless needle crystals (known as ligusticum cycloprolactam, LIGc) through the structural modification of LIG. After a stability experiment was conducted at room temperature for four months, no impurity peaks were found by HPLC-DAD analysis, which indicated that LIGc resolved the stability issues of LIG. LIGc was absorbed and eliminated rapidly after intravenous administration (Cmax = 6.42 ± 1.65 mg/L at a dose of 20 mg/kg) and oral administration (Tmax = 0.5 h, Cmax = 9.89 ± 1.62 mg/L at a dose of 90 mg/kg, t1/2z approximately 2.5 h). The absolute oral bioavailability (F) of LIGc was clearly higher than the F of LIG reported in the literature (F, 83.97 % versus 2.6 %). Linear dose-dependent pharmacokinetics were observed after oral administration, with a higher area under the curve (AUC0-t, 22.31 ± 2.88 mg/L*h) observed at 90 mg/kg than that at 45 mg/kg (AUC0-t, 13.673 ± 0.666 mg/L*h). Tissue distribution results indicated that LIGc easily crossed the blood-brain barrier (BBB) and was distributed widely to the main tissues and organs of rats. We also conducted a preliminary safety assessment of LIGc by means of an acute toxicity test in KM mice. All mice had excellent health status (ig, dosage of 5.0 g/kg), with no histopathological changes observed in the main organs.

Synthesis, crystal structure, and non-covalent interactions in 4-hydrazinobenzoic acid hydrochloride

The compound 4-hydrazinobenzoic acid hydrochloride (4-HBA), C7H9O2·Cl, has been synthesized and characterized by FT-IR spectroscopy and X-ray diffraction. The compound crystallizes as colourless needles in a triclinic system, space group Pˉ1 (Z = 2), and cell parameters a = 3.7176 (4) Å, b = 5.9133 (4) Å, c = 19.3631 (13) Å, α = 87.841 (6), β = 88.924 (6), γ = 80.203 (6), V = 419.13 (6) Å3. The component ions are linked by a combination of O–H⋯O, N–H⋯N and N–H⋯Cl hydrogen bonds to form a complex three-dimensional framework structure in which each cation is linked to two other cations, by O–H⋯O and N–H⋯N hydrogen bonds, and to five different anions, while each anion accepts hydrogen bonds from five different cations. Calculations on the Non-Covalent Interactions (NCI) amplify the crystallographic conclusions concerning the interionic hydrogen bonds.

Discrete [Yb(NCS)3(H2O)5] Molecules in Pentaaquatriisothiocyanatoytterbium(III) Monohydrate

Single crystals of [Yb(NCS)3(H2O)5]·H2O were synthesized from a salt‐metathesis reaction between stoichiometric amounts of aqueous solutions of Yb2(SO4)3·8H2O and Ba(NCS)2·3H2O driven by the precipitation of Ba(SO4), followed by isothermic evaporation of the filtered‐off solution at room temperature under atmospheric conditions. These crystals of the title compound came as transparent, colorless and hygroscopic needles. According to the X‐ray diffraction structure analysis [Yb(NCS)3(H2O)5]·H2O crystallizes in the monoclinic space group P21 with the lattice parameters a = 845.38(5), b = 719.26(4), c = 1219.65(7) pm, β = 103.852(3)° for Z = 2. The acentric crystal structure contains crystallographically unique Yb3+ cations, each surrounded by three thiocyanate anions, all grafting with their nitrogen atoms, and five water molecules forming a neutral [Yb(NCS)3(H2O)5] complex with square antiprismatic shape, completed by a sixth interstitial water molecule. ATR‐FT infrared and single‐crystal Raman spectra of [Yb(NCS)3(H2O)5]·H2O confirm these findings.

The solid-state conformation of the topical antifungal agent O-naphthalen-2-yl N-methyl-N-(3-methylphenyl)carbamothioate.

Tolnaftate, a classic antifungal compound, has been found to crystallize from 1:1 (v/v) acetone-water as large flat colorless needles in the centrosymmetric monoclinic space group P21/c. These crystals contain a 50:50 mixture of the (+ap,-sp,+ac,-ac) and (-ap,+sp,-ac,+ac) conformers. The bond lengths in the central CNOS unit are 1.3444 (19), 1.3556 (18) and 1.6567 (15) Å for C-N, C-O and C-S, respectively, and the CNOS and C3N moieties are flat and nearly coplanar with each other, consistent with the C-N bond possessing partial double-bond character. Tolnaftate and the four most closely related N,N-disubstituted thiocarbamates in the Cambridge Structural Database (CSD) all exist as E-conformational isomers in the solid state. Among these five compounds, tolnaftate is the only one in which the N-tolyl moiety is positioned trans to the S atom, i.e. the N-aryl substituent in each of the other compounds is positioned cis to their respective S atom. Notably, and more importantly, our experimental X-ray structure is unlike all prior theoretical models available for tolnaftate. The implication, either directly or indirectly, is that some of those theoretical models used in earlier studies to explain the spectroscopic properties of tolnaftate and to suggest which protein-ligand interactions are responsible for the binding of tolnaftate to squalene epoxidase are either inappropriate or structurally unreasonable, i.e. the results and conclusions from those prior studies are in need of critical reassessment.

Determination of the Hydrogen Positions in the Novel Barium Boroarsenate Ba[B2As2O8(OH)2] by Combined Single Crystal X‐ray and Powder Neutron Investigations

The boroarsenate Ba[B2As2O8(OH)2] was obtained by the reaction of NH4H2AsO4, B(OH)3 and BaBr2·2H2O in the melt. Ba[B2As2O8(OH)2] was obtained as thin colorless needles, together with spherical crystals of BAsO4 as by‐product, grown on a pellet of Ba[BAsO5]. The products could be separated mechanically. For neutron scattering experiments a sample was prepared with 11B(OH)3 as a starting material. The crystal structure of Ba[B2As2O8(OH)2] was determined by single‐crystal X‐ray diffraction and exhibits a layer structure with an unprecedented layer topology. The exact positions of the hydrogen atoms were determined using combined single‐crystal X‐ray and powder neutron diffraction investigations. Ba[B2As2O8(OH)2] was further characterized by IR spectroscopy and EDX analysis.

Synthesis, characterization and crystal structure of (2RS,4R)-2-(2-hydroxy-3-methoxyphenyl)thiazolidine-4-carboxylic acid

The condensation reaction of ortho-vanillin and l-cysteine leads to formation of a racemic mixture of (2RS,4R)-2-(2-hydroxy-3-methoxyphenyl)thiazolidine-4-carboxylic acid and not, as reported in the available literature, to a Schiff base. The racemic mixture was fully characterized by 1D and 2D NMR techniques, ESI-MS and X-ray diffraction. Addition of ZnCl2 led to formation of crystals in form of colorless needles, suitable for X-ray diffraction studies. The measured crystals were identified as the diastereomer (2R,4R)-2-(2-hydroxy-3-methoxyphenyl)thiazolidine-4-carboxylic acid 1. The bulk material is racemic. Thiazolidine exists as zwitterion in solid state, as indicated by the crystal structure.

A new polymorph of 2,6-diaminopyridine.

2,6-Diaminopyridine (26-DAP, C5H7N3) is a common intermediate in the synthesis of aromatic azo chromophores, which are widespread in the dyes and pigments industry. Sublimation of commercial 26-DAP powder yielded a new polymorph, denoted Form II, which grew as colorless orthorhombic needles. Recrystallization from acetone or toluene also yielded Form II as the major phase. Thermal analysis shows that Form II is a less stable polymorph and it converts upon heating at 335 K to the previously reported Form I.

Synthesis and Characterization of Coordination Compounds of Silver(I) Nitrite with Ligands Ethylenethiourea and N,N'-diethylthiourea

Silver(I) nitrate and ethylenethiourea ( etu) in 1 : 4 stochiometry have been reported [1]. Coordination compounds of A and B as silver(I) nitrite with etu and silver(I) nitrite with N,N’ -diethylthiourea ( detu) respectively, have never been done. The purposes of this study are to synthesize and characterize coordination compounds of A and B. Synthesis coordination compound of A with 1 : 4, while B with 1 : 2 stoichiometry. Both of coordination compounds are conducted directly in acetonitrile. Compounds obtained are characterized by melting point, electrical conductivity measurement, SEM-EDX , qualitative nitrite test, free energy calculation and structures prediction using Spartan’14 v1.1.0 . Coordination compounds of A and B are colourless needle and prism crystals; have melting point of 189°C and 103-105°C; free energy of -289,2567 and -1182.8101 kJ/mol respectively. Electrical conductivity measurement and qualitative nitrite test show that the obtained compound of A is an ionic and B is a molecular one. EDX analysis gives empirical formula prediction of two coordination compound A is C 12 H 24 AgN 9 O 2 S 4 and B is C 15 H 36 AgN 7 O 2 S 3 .

The crystal structure of Cs2S2O3·H2O

AbstractA reinvestigation of the alkali metal thiosulfates has led to the new phase Cs2S2O3·H2O. At first cesium thiosulfate monohydrate was obtained as a byproduct of the synthesis of Cs4In2S5. Further investigations were carried out using the traditional synthesis reported by J. Meyer and H. Eggeling. Cs2S2O3·H2O crystallizes in transparent, colorless needles. The crystal structure of the title compound was determined by single crystal X-ray diffraction at room temperature: space groupC2/m(No. 12), unit cell dimensions:a= 11.229(4),b= 5.851(2),c= 11.260(5) Å,β= 95.89(2)°, withZ= 4 and a cell volume ofV= 735.9(5) Å3. The positions of all atoms including the hydrogen atoms were located in the structure refinement. Cs2S2O3·H2O is isotypic with Rb2S2O3·H2O. Isolated tetrahedra [S2O3]2−are coordinated by the alkali metal cations, and in addition they serve as acceptors for hydrogen bonding. For both Cs atoms the shortest distances are observed to oxygen atoms of the S2O32−anions whereas the terminating sulfur atom has its shortest contacts to the water hydrogen atoms. Thus, an extended hydrogen bonding network is formed. The title compound has also been characterized by IR spectroscopy. IR spectroscopy reveals the vibrational bands of the water molecules at 3385 cm−1. They show a red shift in the OH stretching and bending modes as compared to free water. This is due both to the S···H hydrogen bonding and to the coordination of H2O molecules to the cesium atoms.

Ultrasonic assisted extraction of ursolic acid from apple pomace: A novel and facile technique

ABSTRACTSubstantial amount of apple pomace (AP) is produced in apple processing industries and is often discarded as waste which becomes a source of polluting the environment. However, the by-product constitutes a promising bioresource of ursolic acid with various biological activities. Therefore, this particular research study was aimed to develop a novel and facile method to separate ursolic acid from AP. First, AP was extracted with ultrasound assistance using methanol as extraction solvent, 2.86% with 10:1 (mL g−1) of liquid–solid ratio, 300 W of ultrasonic power, 50°C of extraction temperature, and 90 min of ultrasonic time. Meanwhile, the disruption effect of ultrasound on AP was observed by scanning electron microscope. Second, a novel and facile method was applied to separation of ursolic acid, then a perfect colorless needle crystal of ursolic acid was obtained with the yield of about 1.34% of dry AP.

Apexite, NaMg(PO4)·9H2O, a new struvite-type phase with a heteropolyhedral cluster

Apexite (IMA2015-002), NaMg(PO 4 )·9H 2 O, is a new mineral from the Apex mine, Lander County, Nevada, U.S.A., where it occurs as a low-temperature secondary mineral on massive quartz matrix in association with andersonite, calcite, cejkaite, gaylussite, and goethite. Apexite forms colorless needles up to 0.5 mm in length. The streak is white. Crystals are transparent and have vitreous to satiny luster. The Mohs hardness is about 2, the tenacity is brittle, the fracture is curved, and crystals exhibit one perfect cleavage on {100}. The measured density is 1.74(1) g/cm 3 and the calculated density is 1.741 g/cm 3 . Electron microprobe analyses provided: Na 2 O 9.26, MgO 14.42, P 2 O 5 23.31, H 2 O 53.01 (structure), total 100.00 wt% (normalized). The empirical formula (based on 13 O apfu) is: Na 0.91 Mg 1.09 P 1.00 O 13.00 H 17.91 . Apexite is triclinic, P 1, a = 6.9296(7), b = 11.9767(13), c = 14.9436(19) A, α = 92.109(6), β = 102.884(7), γ = 105.171(7)°, V = 1160.9(2) A 3 , and Z = 4. The eight strongest lines in the X-ray powder diffraction pattern are [ d obs in A( I )( hkl )]: 14.63(35)(001); 5.11(61)(021,1 11,110,120); 4.68(75)(022,1 12,121,013); 4.301(96)(102,013,022,113); 4.008(44)(1 13,122); 2.876(46)(040); 2.762(100)(2 13,231,034,204,015); and 2.507(30)(212,025,2 23). Apexite is a new struvite-type phase with a unique structure ( R 1 = 4.44% for 1401 F o > 4σ F ) consisting of four components: (1) a [Na 2 Mg 4 (H 2 O) 14 ] 10+ heteropolyhedral cation cluster; (2) a trans edge-sharing chain of Na(H 2 O) 6 octahedra; (3) an isolated PO 4 group; and (4) an isolated H 2 O group. The structural components are linked to one another only via hydrogen bonds. Its structure is related to that of hazenite.

Experimental and Theoretical Studies of 4‐(1‐benzyl‐5‐methyl‐1H‐1,2,3‐triazol‐4‐yl)‐6‐(2,4‐dichlorophenyl)pyrimidin‐2‐amine: A Potential Antibacterial Agent

AbstractThe title compound (1), 4‐(1‐benzyl‐5‐methyl‐1H‐1,2,3‐triazol‐4‐yl)‐6‐(2,4‐dichlorophenyl)pyrimidin‐2‐amine (C20H16Cl2N6), was synthesized and structurally characterized by elemental analysis, 1H NMR and 13C NMR and single crystal X‐ray diffraction. The compound crystallizes as a colourless needle shaped in the triclinic system, space group P‐1 with cell constants: a = 10.7557(11) Å, b = 12.7078(17) Å, c = 15.511(2) Å, α = 68.029(4)0, β = 86.637(5)0, γ = 87.869(4)0; V = 1962.4 (4) Å3, Z = 4. There are two structurally similar but crystallographically independent molecules (A and B) in the asymmetric unit of the title compound, which is linked via N‐H…Cl hydrogen bond. An intramolecular C‐H…N hydrogen also occurs in each molecule. In the crystal, each of independent molecules forms a centrosymmetric dimer with an R22(8) ring motifs through a pair of N‐H…N hydrogen bonds. These dimers are further connected by intermolecular N‐H…Cl and C‐H…Cl hydrogen bonds, forming an infinite two dimensional supramolecular network lying parallel to the [010] plane. The molecular geometry was also optimized using density functional theory (DFT/B3LYP) method with the 6‐311G (d, p) basis set and compared with the experimental data. Mulliken population analyses on atomic charges, HOMO‐LUMO energy levels, Molecular electrostatic potential and chemical reactivity of the title compound were investigated by theoretical calculations. The thermo dynamical properties of the title compound at different temperature have been calculated and corresponding relations between the properties and temperature have also been obtained. The in vitro antibacterial activity has been screened against Gram‐positive (Bacillus cerus and Staphylococcus epidermidis) and Gram‐Negative (Escherichia coli, Acinetobacter baumannii and Proteus vulgaris). The results revealed that the compound exhibited good to moderate antibacterial activity.

Spectroscopic and Thermogravimetric Characterization of Pb(II) Dinonyldithiophosphate: Removal of Pb(II) from Aqueous Solution

Dinonyldithiophosphoric acid (DNDTPA) was prepared by adding phosphorus pentasulfide to nonyl alcohol. The lead dinonyl dithiophosphate complex Pb(DNDTP) 2 was prepared by mixing a solution of lead(II) with a solution of DNDTPA in ethanol at room temperature. The recovered Pb(DNDTP) 2 was crystallized in ethanol, and fi ne colorless needles were obtained. The complex was characterised by elemental analysis and IR, UV–vis and atomic absorption spectroscopy. The thermal behavior of Pb(DNDTP) 2 was investigated by thermogravimetric analysis under a nitrogen atmosphere. Removal of Pb(II) from aqueous media by DNDTPA solutions was investigated. The optimum conditions for extraction, such as the organic solvent, pH of the aqueous phase, time of equilibration, concentration, and effect of anions, were investigated. It was found that DNDTPA is an effective substance for removing Pb(II) from aqueous solution.

X-ray structures of precursors of styrylpyridine-derivatives used to obtain 4-((E)-2-(pyridin-2-yl)vinyl)benzamido-TEMPO: synthesis and characterization.

The synthesis and characterization of the precursor isomers trans-4-(2-(pyridin-2-yl)vinylbenzaldehyde (I), trans-4-(2-(pyridin-4-yl)vinylbenzaldehyde (II), trans-4-(2-(pyridin-2-yl)vinylbenzoic acid (III) and (E)-4-(2-(pydridin-4-yl)vinylbenzoic acid (IV) are reported. These compounds were prepared in order to obtain trans-4-((E)-2-(pyridin-2-yl)vinyl)benzamide-TEMPO (V). Compounds I and II were obtained by using a Knoevenagel reaction in the absence of a condensing agent and solvent. Oxidation of the aldehyde group using the Jones reagent afforded the corresponding acid forms III and IV. A condensation reaction with 4-amino-TEMPO using oxalyl chloride/DMF/CH2Cl2 provided the 4-((E)-2-(pyridin-2-yl)vinyl)benzamide-TEMPO. Single crystals of compounds I, II and III were obtained and characterized by X-ray diffraction. Compound I belongs to space group P21/c, a = 12.6674(19) Å, b = 7.2173(11) Å, c = 11.5877(14) Å, β = 97.203(13)° and the asymmetric unit was Z = 4, whereas compound II was in the space group P21, with a = 3.85728(9) Å, b = 10.62375(19) Å, c = 12.8625(2) Å, β = 91.722 (2)° and the asymmetric unit was Z = 2. Compound III crystallized as single colorless needle crystals, belonging to the monoclinic system with space group P21, with Z = 2, with a = 3.89359(7) Å, b = 17.7014(3) Å, c = 8.04530(12) Å, β = 94.4030 (16)°. All compounds were completely characterized by IR, 1H-NMR, EI-MS and UV-Vis.