Synthesis and structural investigation of mono- and polynuclear copper complexes of 4-ethyl-1-(pyridin-2-yl) thiosemicarbazide

The reaction between 2-hydrazinopyridine and ethylisothiocyanate produced 4-ethyl-1-(pyridin-2-yl) thiosemicarbazide (HEPTS). Its reaction with copper fluoride, chloride, bromide, acetate, nitrate, perchlorate, sulfate, carbonate, hydroxide and copper metal produced 15 Cu(II) complexes. The copper metal is easily oxidized in aqueous-ethanol solution of HEPTS giving [Cu(2)(EPTS)(H(2)O)(3)(OH)(3)]EtOH. Different complexes for the same anion were synthesized by controlling the heating time. Characterization by elemental, thermal, magnetic and spectral (electronic, IR, mass and ESR) studies showed the formation of mono-, di-, tri- and tetra nuclear complexes. The room temperature solid state ESR spectra of the complexes show an axial spectrum with d(x)(2)-y(2) ground state, suggesting distorted tetragonal geometry around Cu(II) center. The kinetic and thermodynamic parameters for the different decomposition steps in the complexes were calculated. HEPTS and its Cu(II) complexes showed high activity against gram negative bacteria; [Cu(3)(EPTS)(2)(EtOH)(2)Br(4)] has more activity.     

Liquid-liquid extraction and cloud point extraction for spectrophotometric determination of vanadium using 4-(2-pyridylazo)resorcinol

Liquid-liquid extraction (LLE) and cloud point extraction (CPE) of vanadium(V) ternary complexes with 4-(2-pyridylazo)resorcinol (PAR) and 2,3,5-triphenyl-2H-tetrazolum chloride (TTC) were investigated. The optimal conditions for vanadium extraction and spectrophotometric determination were identified. The composition (V: PAR: TTC) of the extracted species was 1:2:3 (optimal conditions; LLE), 2:2:2 (low reagents concentrations; LLE), 1:1:1 (short heating time;CPE), and 1: 1: 1 + 1: 1: 0 (optimal extraction conditions; CPE). LLE, performed in the presence of 1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid and NH₄F as masking agents, afforded the sensitive, selective, precise, and inexpensive spectrophotometric determination of vanadium. The absorption maximum, molar absorptivity, limit of detection, and linear working range were 559 nm, 1.95 × 10⁵ dm³ mol^?1 cm^?1,0.7 ng cm^?3, and 2.2–510 ng cm^?3, respectively. The procedure thus developed was applied to the analysis of drinking waters and steels. The relative standard deviations for V(V) determination were below 9.4 % (4–6 × 10^?7 mass %; water samples) and 2.12 % (1–3 mass %; steel samples).     

Cloud point extraction and simultaneous spectrophotometric determination of V(V), Co(II) and Cu(II) ions in water samples by 5-Br-PADAP using partial least squares regression

In this work, a new method has been proposed to simultaneously determine V(V), Co(II) and Cu(II) ions from aqueous solution by spectrophotometry after cloud point extraction using partial least squares regression (PLS). The metal ions in 10 ml of aqueous solution (containing 0.2 M sodium acetate buffer solution, pH 3.5) were formed complexes with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP). Then, Triton X-114 (2 %, v/v) was added to the solution. By increasing the temperature of the solution up to 55 °C, a phase separation occurred. After centrifugation at 3,000 rpm for 10 min, the surfactant-rich phase was dissolved and diluted to 0.5 mL with ethanol. The metal ions were then determined using spectrophotometry. At these optimal extraction and operating conditions, linearity was obeyed in the range 7–300, 3–100 and 15–700 ng mL^?1 of V(V), Co(II) and Cu(II), with the detection limit of 2.2, 1.0 and 4.5 ng mL^?1, respectively. The relative predictive error for the simultaneous determination of 15 test samples of different concentrations of V(V), Co(II) and Cu(II) was 3.28, 3.64 and 4.04 %, respectively. The root mean square error of prediction for applying the PLS method to 15 synthetic samples in the linear ranges of these metal ions was 3.4, 1.6 and 18.1 ng mL^?1. The interference effect of some anions and cations was also tested. The proposed method has been applied successfully to the simultaneous determination of V(V), Co(II) and Cu(II) ions in real matrix samples with the recoveries of 96.75–104.80 %.     

Mixed-Anion Cu(II) Complexes with 3-(pyridin-2-yl)pyrazole (L), Syntheses and X-ray Crystal Structure of [Cu(L)2 Br]ClO4 (L=3-(pyridin-2-yl)pyrazole)

Reaction of the ligand 3-(pyridin-2-yl)pyrazole (L) with Cu(ClO₄)₂ and CuX₂ (X=Cl, Br, I) gives complexes with stoichiometry [Cu(L)₂X]ClO₄ (X = Cl, Br, I). The new complexes were characterized by elemental analyses and infrared and electronic spectroscopy. The crystal structure of the [Cu(L)₂Br]ClO₄ was determined by X-ray crystallography. The cation complex (i.e. [Cu(L)₂Br]P) contains copper(II) with a distorted trigonal bipyramid geometry with a Br^― ligand occupying an equatorial site. The penta-coordinated metal atom is bonded to two pyridinic nitrogens, two pyrazolic nitrogens, and one bromide anion. The pyrazolic H atoms are hydrogen bonded to Br atoms, resulting in infinite hydrogen-bonded chains running in the b direction. There are π‐π stacking interactions (charge-transfer arrays) between the parallel aromatic rings belonging to adjacent chains that may help to form hydrogen bonding in the coordination geometry around Cu (II).     

Stopped-flow spectrophotometric determination of nM level of Pb(II) using 5,10,15,20-terakis(1-methylpyridinium-4-yl)porphine

A spectrophotometric determination method for nM levels of Pb(II) has been developed using a stopped-flow spectrophotometer with cationic water-soluble porphyrin. The stopped-flow spectrophotometer allows the monitoring of the incorporation reaction of the Pb(II) ion into 5,10,15,20-terakis(1-methylpyridinium-4-yl)porphine (TMPYP) within a narrow time window (2.5 s) at pH 10.5–12.0 before the Pb-TMPYP complex is replaced with other foreign metal ions, since usually the Pb-TMPYP complex is very labile and readily replaced with other metal ions. This improved the selectivity of Pb(II) determination as compared to the conventional spectrophotometric determination of Pb(II) using water-soluble porphyrins.     

Selective solid-phase extraction of Cu(II) using freshly precipitated lead diethyldithiocarbamate and its spectrophotometric determination

A new solid-phase extraction method has been developed for the selective extraction of Cu(II) in an aqueous system using freshly precipitated lead diethyldithiocarbamate (Pb(DDTC)₂) as a reagent. The method is based on the quantitative replacement of Pb(II) ions in the solid Pb(DDTC)₂ phase by Cu(II) ions present in aqueous phase. The obtained solid Cu(DDTC)₂ phase was dissolved in chloroform and determined spectrophotometrically at 435 nm. Beer’s law was obeyed over the concentration range of 0.2–5 mg dm⁻³. The molar absorptivity and the Sandell’s sensitivity coefficients of the solutions were 1.0689 × 10⁴ dm³ mol⁻¹ cm⁻¹ and 0.0060 μg cm⁻², respectively. The optimum conditions for each parameter were experimentally determined and possible interferences of various salts were also studied. The method has been validated and applied to determine Cu(II) in various alloys and water samples.     

One-pot synthesis of 3-(pyridin-2-yl)-2,3-dihydroazetes via Rh(II)-catalyzed reaction of diazoesters with trimethylsilyl-protected 2-(pyridin-2-yl)-2H-azirines

Chemistry of Heterocyclic Compounds - A one-pot method for the synthesis of 3-(pyridin-2-yl)-2,3-dihydroazetes was developed on the basis of Rh2(esp)2-catalyzed reaction of diazoesters with...     

Synthesis of 1-(pyridin-4-yl)-3,6-diazahomoadamantane and its derivatives

Condensation of 1-(pyridin-4-yl)propan-2-one with 1,3,6,8-tetraazatricyclo[4.4.1.1^3,8]dodecane gave 1-( pyridin-4-yl)-3,6-diazahomoadamantan-9-one as intermediate product in the synthesis of 1-(pyridin-4-yl)-3,6-diazahomoadamantane and its derivatives having functional substituents at the bridging carbon atom in the homoadamantane skeleton.     

Copper(II) complex with 6-(3,5-dimethyl-1H-pyrazol-1-yl)-2-(pyridin-2-yl)pyrimidin-4-amine: synthesis,crystal structure,and electronic spectroscopy

A copper(II) complex with 6-(3,5-dimethyl-1H-pyrazol-1-yl)-2-(pyridin-2-yl)pyrimidin-4-amine (L), [CuLCl₂], has been synthesized. This compound is formed irrespective of the Cu?:?L molar ratio (Cu?:?L?=?1?:?1, 2?:?1, and 20?:?1) in the MeOH/H₂O/DMF mixture as a single product. ESI-MS data demonstrate that the additional amount of CuCl₂ above the Cu?:?L?=?1?:?1 molar ratio, is effectively solvated, and high-nuclearity species are formed in trace amounts in the solution. The complex adopts a distorted square-pyramidal geometry with two chlorides and three nitrogen atoms from L. The electronic spectrum of the complex contains a broad band with a maximum at 12,820?cm^?1 within the region characteristic for square-pyramidal chromophores CuA₅ (A?=?Cl, N). Due to Cu?···?Cl contacts, the molecules of [CuLCl₂] form the dinuclear [CuLCl₂]₂ unit. Surprisingly, the NH₂-group participates in the formation of NH?···?Cl hydrogen bonds instead of the formation of (NH?···?N3_(pyrimidine))₂ synthon, which is common for N-heteroaromatic compounds containing the NH₂-group in the α-position to aza-atom. These hydrogen bonds together with Cu?···?Cl contacts result in the formation of a 3-D-structure.     

1-(2'-苯并噻唑)-3-(4'-羧基苯)三氮烯固相萃取分光光度法测定钯

根据新试剂1-(2'-苯并噻唑)-3-(4'-羧基苯)三氮烯(BTCBT)与钯的显色反应及C8固相萃取小柱对显色络合物的固相萃取,建立了一种测定痕量钯的新方法,在pH为5.0～6.3的柠檬酸氢二钠-NaOH缓冲介质中,在乳化剂OP和SDBS存在下,钯与BTCBT发生反应形成1∶2的稳定络合物,该络合物可用C8固相萃取小柱富集,小柱上富集的络合物用乙醇洗脱后用分光光度法测定,在富集后的测定液中,络合物最大吸收波长为490 nm,摩尔吸光系数ε=1.16×105 L·mol-1·cm-1,Pd2 量在0.1～1.2 μg/mL内符合比尔定律,方法适用于测定催化剂中的钯.     

Cloud point extraction and spectrophotometric determination of codeine in pharmaceutical and biological samples

Cloud point extraction process using non-ionic surfactant, Triton X-114, to extract codeine from aqueous solution was investigated. The method was based on the extraction of codeine and bromothymol blue from acetate buffer media to surfactantrich phase and formed a charge transfer-ion pair complex. The extracted surfactant-rich phase was diluted with ethanol and its absorbance was measured at 430 nm. The effect of different variables such as pH, Triton X-114 concentration, cloud point temperature and time was established. The calibration graph was linear in a wide range of 100–700 ng ml^?1 of codeine with r = 0.998 (n = 7). The detection limit based on three times standard deviation of the blank (3s) was 4.6 ng ml^?1 and relative standard deviation (R.S.D) is 2.15% for 500 ng ml^?1 codeine (n = 5). The proposed method was applied to the determination of codeine in acetaminophen codeine tablets and blood samples.     

Simultaneous spectrophotometric determination of Zinc(II) and Nickel(II) with 1-(2-pyridylazo)-2-naphthol

A new procedure for the simultaneous spectrophotometric determination of Zn(II) and Ni(II) with 1-(2-pyridylazo)-2-naphthol as chromogenic reagent has been developed. It is based on resolution of the mixed spectrum over the wavelength range 530–590 nm by applying a least-squares fitting program to standard spectra from each component. The spectra are recorded at an apparent pH of 5.0, provided by an acetate buffer in a mixed 6040 v/v 2-ethoxyethanol/water medium. The relative standard deviations for determination of 13.7 g of Ni and 31.0 g of Zn were 1.9 and 1.0%, respectively (8 replications). The method has been applied to the analysis of iron surfaces coated with a Zn-Ni alloy. The results are compared with those obtained by atomic-absorption spectrophotometry.     

新的吡啶基硫醚苯甲酸的原位合成及其铜配合物

在氧化铜和溴化铜存在的条件下, 4-[1,2-(2-吡啶基)亚甲硫基]-苯甲酸(L′)经原位消去反应, 形成了一个新的有机配体4-[1,2,2-(2-吡啶基)-(2-吡啶亚甲基)亚甲硫基]-苯甲酸(L), 并与铜形成配位聚合物[Cu₂(L)Br₂]_n(1){L=4-[1,2,2-(2-吡啶基)-(2-吡啶亚甲基)亚甲硫基]-苯甲酸}, 通过红外光谱、元素分析和X射线单晶衍射等手段对其结构进行了表征.     

Synthesis of 6-Methyl-4-(1-methyl-2-buten-1-yl)-2-(2-cyclohexen-1-yl)- and 6-Methyl-4-(1-methyl-2-buten-1-yl)-2-(1-cyclohexen-1-yl)anilines

Alkenylation of 6-methyl-2-(2-cyclohexen-1-yl)- and 2-(1-cyclohexen-1-yl)anilines with piperylene in the presence of AlCl₃ and transformation of the resulting cyclohexenylanilines into carbazole structures were studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3, 2005, pp. 441–443.Original Russian Text Copyright © 2005 by Gataullin, Ishberdina, Sotnikov, Abdrakhmanov.     

Rapid spectrophotometric determination of manganese(II) with 4-(2-thiazolylazo)-resorcinol

Summary Manganese forms a red chelate with 4-(2-thiazolylazo)-resorcinol at pH 8.8 (borate buffer), and absorbance is measured after 30 s, at 540 nm in the presence of 20%tert-butyl alcohol (by volume). The 12 complex obeys Beer's law for manganese concentration of 0.04–1.4g per ml, has molar absorptivity 4.176 x 10⁴ and Sandell sensitivity 0.0013g cm^–2. The formation constant (logK) is found to be 9.32, and relative standard deviation ±0.22%. Of the 48 ions studied for interference, only Co(II), Zn(II), Cd(II), Pb(II) and EDTA^2– are found to interfere. This method has been applied for the determination of manganese content in alloy steels.

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Spektrophotometrische Bestimmung von Mangan(II) mit 4-(2-Thiazolylazo)-resorcin

Zusammenfassung Mangan bildet bei pH 8,8 (Boratpuffer) mit 4-(2-Thiazolylazo)-resorcin ein rotes Chelat, dessen Absorbanz nach 30 sec bei 540 nm in Gegenwart von 20% tert. Butylalkohol gemessen wird. Dieser 12-Komplex entspricht bei einer Mangan-Konzentration von 0,04–1,4g/ml dem Beerschen Gesetz; seine molare Absorption beträgt 4,176 x 10⁴, die Empfindlichkeit nach Sandell 0,0013g·cm^–2. Die Bildungskonstante (log K) beträgt 9,32, die rel. Standardabweichung ±0,22%. Unter 48 untersuchten Ionen erwiesen sich nur Co(II), Zn(II), Cd(II), Pb(II) und EDTA als störend.-Das Verfahren wurde zur Bestimmung des Mangangehaltes in Stahl verwendet.

     

合成3-羟基-2-(4-吡啶基)-1H-茚-1-酮的工艺改进

以邻苯二甲酸酐和4-甲基吡啶为起始原料,正十二烷为溶剂,氯化锌为催化剂,于190℃反应24 h合成了抗癌药物瓦他拉尼的关键中间体——3-羟基-2-(4-吡啶基)-1H-茚-1-酮,收率90.6%,其结构经1H NMR,IR和MS确证。     

Extractive spectrophotometric determination of tungsten(VI) using 3-hydroxy-2-(2'-thienyl)-4-oxo-4H-1-benzopyran

A simple, rapid, highly sensitive and selective spectrophotometric method for the determination of tungsten(VI) in trace amounts is developed using 3-hydroxy-2-(2'-thienyl)-4-oxo-4H-1-benzopyran (HTB) as a reagent for the complexation of metal ion and extracting the 1:2 (metal:ligand) complex into dichloromethane from 0.2 M HCl solution. It obeys Beer's law in the range 0-2.8 microg Wml(-1) with molar absorptivity and Sandell's sensitivity at 415 nm as 6.45 x 10(4) L mol(-1) cm(-1) and 0.0029 microg W(VI) cm(-2), respectively. The method is free from the interference of a large number (39) of elements and handles satisfactorily the analysis of various samples of varying complexity.     

N-(S)-(1'-氯甲基-2'-烷基)-2-乙基-2-(4S-烷基-4,5-二氢恶唑)丁酰胺的合成

由L-氨基酸不对称合成了4种新型手性化合物(6a，6b，7a，7b)，其结构经IR，^1HNMR，^1^3C NMR及MS等证实。     

DFT studies on tautomeric preferences of 1-(pyridin-2-yl)-4-(quinolin-2-yl)butane-2,3-dione in the gas phase and in solution

Density functional theory (DFT) calculations show that in vacuum such α-diketone as 1-(pyridin-2-yl)-4-(quinolin-2-yl)butane-2,3-dione is much less stable than its enolimine–enaminone ((1Z,3Z)-3-hydroxy-4-(pyridin-2-yl)-1-(quinolin-2(1H)-ylidene)but-3-en-2-one) and dienaminone tautomers ((1Z,3Z)-1-(pyridin-2-yl)-4-(quinolin-2-yl)buta-1,3-diene-2,3-diol). Other its tautomers (multiple basic and acidic centers in their molecules enable multiple proton transfer to take place) are even more labile. Strength of the intramolecular hydrogen bonds and aromatic character of the (quasi)rings [proved by the Harmonic Oscillator Model of Aromaticity (HOMA) index] in their molecules were found to be responsible for the observed tautomeric preferences. Polar and basic solvent disfavors and favors the enolimine and enaminone tautomers, respectively.     

Synthesis of 2-(pyridin-3-yl)-1-azabicyclo[3.2.2]nonane, 2-(pyridin-3-yl)-1-azabicyclo[2.2.2]octane, and 2-(pyridin-3-yl)-1-azabicyclo[3.2.1]octane, a class of potent nicotinic acetylcholine receptor-ligands

In an attempt to generate nicotinic acetylcholine receptor (nAChR) ligands selective for the alpha4beta2 and alpha7 subtype receptors we designed and synthesized constrained versions of anabasine, a naturally occurring nAChR ligand. 2-(Pyridin-3-yl)-1-azabicyclo[2.2.2]octane, 2-(pyridin-3-yl)-1-azabicyclo[3.2.2]nonane, and several of their derivatives have been synthesized in both an enantioselective and a racemic manner utilizing the same basic synthetic approach. For the racemic synthesis, alkylation of N-(diphenylmethylene)-1-(pyridin-3-yl)methanamine with the appropriate bromoalkyltetrahydropyran gave intermediates which were readily elaborated into 2-(pyridin-3-yl)-1-azabicyclo[2.2.2]octane and 2-(pyridin-3-yl)-1-azabicyclo[3.2.2]nonane via a ring opening/aminocyclization sequence. An alternate synthesis of 2-(pyridin-3-yl)-1-azabicyclo[3.2.2]nonane via the alkylation of N-(1-(pyridin-3-ylethylidene)propan-2-amine has also been achieved. The enantioselective syntheses followed the same general scheme, but utilized imines derived from (+)- and (-)-2-hydroxy-3-pinanone. Chiral HPLC shows that the desired compounds were synthesized in >99.5% ee. X-ray crystallography was subsequently used to unambiguously characterize these stereochemically pure nAChR ligands. All compounds synthesized exhibited high affinity for the alpha4beta2 nAChR subtype ( K i < or = 0.5-15 nM), a subset bound with high affinity for the alpha7 receptor subtype ( K i < or = 110 nM), selectivity over the alpha3beta4 (ganglion) receptor subtype was seen within the 2-(pyridin-3-yl)-1-azabicyclo[2.2.2]octane series and for the muscle (alpha1betagammadelta) subtype in the 2-(pyridin-3-yl)-1-azabicyclo[3.2.2]nonane series.