Indium determination in different environmental materials by electrothermal atomic absorption spectrometry with Amberlite XAD-2 coated with 1-(2-pyridylazo)-2-naphthol

Methods were developed for indium (In) determination in complex ores by electrothermal atomization atomic absorption spectrometry using matrix modification after its separation with Amberlite XAD-2 coated with 1-(2-pyridylazo)-2-naphthol (PAN). Palladium-magnesium, nickel, and zinc nitrates were used as matrix modifiers and were compared in terms of maximum pyrolysis temperature, sensitivity and background signal. They have enhanced the absorption signals for indium, respectively eliminating the matrix interferences. The standard additions method was applied. The relative standard deviations for six replicate determinations were in the range 0.3-4.0% for indium in different ores samples for indium concentrations 7.6-209 μg g⁻¹. The recommended method was applied to the indium determination in real samples. The data obtained by this method were in good agreement with those obtained by ICP-AES.     

3-(Aryl)-2-sulfanylpropenoates of mercury(II) and phenylmercury(II)

Compounds [HQ]₂[Hg(L)₂] and [HQ][PhHg(L)] [where HQ = diisopropylammonium cation; L = pspa, fspa, tspa, where p = 3-(phenyl), f = 3-(2-furyl), t = 3-(2-thienyl), and spa = 2-sulfanylpropenoato] have been prepared by the reaction of mercury(II) acetate or phenylmercury(II) acetate with the corresponding acid in the presence of diisopropylamine in ethanol. The compounds have been characterized by elemental analysis, FAB mass spectrometry and IR and NMR (¹H, ¹³C) spectroscopy. The crystal structures of the [HQ]₂[Hg(L)₂] compounds show the presence of diisopropylammonium cations and [Hg(L)₂]²⁻ anions. In each anion the Hg atom is in an HgO₂S₂ environment and this can be described as nido-tbp. The crystal structures of the [HQ][PhHg(L)] compounds show the presence of diisopropylammonium cations and [PhHg(L)]⁻ anions in which the Hg atom adopts an HgCOS distorted T-environment. The NMR data suggest that the coordination mode of the ligand L²⁻ determined by X-ray diffractometry in the solid remains in solution.     

Construction of a new Cu2+ coated wire ion selective electrode based on 2-((2-(2-(2-(2-hydroxy-5-methoxybenzylidene amino)phenyl)disufanyl)phenylimino)methyl)-4-methoxyphenol Schiff base

In this article a new coated platinum Cu²⁺ ion selective electrode based on 2-((2-(2-(2-(2-hydroxy-5-methoxybenzylideneamino)phenyl)disufanyl)phenylimino) methyl)-4-methoxyphenol Schiff base (L₁) as a new ionophore is described. This sensor has a wide linear range of concentration (1.2 × 10⁻⁷-1.0 × 10⁻¹ mol L⁻¹) and a low detection limit of 9.8 × 10⁻⁸ mol L⁻¹of Cu(NO₃)₂. It has a Nernstian response with slope of 29.54 ± 1.62 mV decade⁻¹ and it is applicable in the pH range of 4.0-6.0 without any divergence in potentioal. The coated electrode has a short response time of approximately 9 s and is stable at least for 3.5 months. The electrode shows a good selectivity for Cu²⁺ ion toward a wide variety of metal ions. The proposed sensor was successfully applied for the determination of Cu²⁺ ion in different real and environmental samples and as indicator electrode for potentiometric titration of Cu²⁺ ion with EDTA.     

Spectrophotometric determination of traces of gallium and indium with 1-(2-pyridylazo)-2-naphthol

1-(2-Pyridylazo)-2-naphthol (PAN) reacts with either gallium or indium at pH 5–6 giving a red complex in an aqueous medium in the presence of N.N-dimethyl-formamide. The maximum absorption of both PAN complexes of gallium and indium in an aqueous solution is at 545 mμ. The gallium-PAN complex shows a characteristic enhancement of color by addition of small amounts of ethers. Based on this selective enhancement reaction, gallium can be determined in the presence of other metals without separation. The results of determining gallium and indium in the presence of each other are reported. Both gallium and indium form M₂(PAN)₃; but in the presence of certain organic solvents, a different gallium complex, Ga(PAN)₅, and the same indium complex, In₂(PAN)₃, are formed. The reaction of PAN with cadmium can be masked by iodide; an example of determining indium in the presence of cadmium is given. The PAN method has a sensitivity of 0.003 μg/cm² for gallium and 0.005μg/cm² for indium and an absorptivity of 24,900 for the Ga-PAN complex and of 24,500 for the In-PAN complex, respectively. The methods have been successfully applied to the determination of both gallium and indium in germanium thin films.     

Synthesis, structural characterization, and reactivity of organolanthanides derived from a new chiral ligand (S)-2-(pyrrol-2-ylmethyleneamino)-2′-hydroxy-1,1′-binaphthyl

Condensation of (S)-2-amino-2′-hydroxy-1,1′-binaphthyl with 1 equiv. of pyrrole-2-carboxaldehyde in toluene in the presence of molecular sieves at 70 °C gives (S)-2-(pyrrol-2-ylmethyleneamino)-2′-hydroxy-1,1′-binaphthyl (1H₂) in 90% yield. Deprotonation of 1H₂ with NaH in THF, followed by reaction with LnCl₃ in THF gives, after recrystallization from a toluene or benzene solution, dinuclear complexes (1)₃Y₂(thf)₂ · 3C₇H₈ (3 · 3C₇H₈) and (1)₃Yb₂(thf)₂ · 3C₆H₆ (4 · 3C₆H₆), respectively, in good yields. Treatment of 1H₂ with Ln[N(SiMe₃)₂]₃ in toluene under reflux, followed by recrystallization from a benzene solution gives the dimeric amido complexes {1-LnN(SiMe₃)₂}₂ · 2C₆H₆ (Ln = Y (5 · 2C₆H₆), Yb (6 · 2C₆H₆)) in good yields. All compounds have been characterized by various spectroscopic techniques, elemental analyses and X-ray diffraction analyses. Complexes 5 and 6 are active catalysts for the polymerization of methyl methacrylate (MMA) in toluene, affording syn-rich poly-(MMA)s.     

Comparative study on 2-amino-1,4-naphthoquinone derived ligands as indium (III) selective PVC-based sensors

The three different ligands (Q₂ to Q₄) based on 2-amino-1,4-naphthoquinone (Q₁), have been synthesized and explored as neutral ionophores for preparing polyvinyl chloride-based membrane sensors selective to indium (III). The addition of potassium tetrakis(4-chlorophenyl) borate and various plasticizers, viz., o-NPOE, DBP, DBBP, DOP and CN has been found to substantially improve the performance of the sensors. The best performance was obtained with the sensor no. 16 having membrane of ligand (Q₂) with composition (%, w/w) ionophore Q₂ (3.0%):PVC (30.0%):o-NPOE (63.0%):KTpClPB (4.0%). This sensor exhibits Nernstian response with slope 19.8 mV/decade of activity in the concentration range 2.5 × 10⁻⁷ to 1.0 × 10⁻² M indium (III), performs satisfactorily over wide pH range of (2.5-7.5) with a fast response time (10 s). The sensor was also found to work satisfactorily in partially non-aqueous media up to 20% (v/v) content of acetonitrile, ethanol and methanol. The proposed sensor can be used over a period of 3.5 months without significant drift in potentials. The quantitative application of sensor was also evaluated by comparative analysis of artificially made sea water with AAS.     

A simple one-step protocol for the olefination of vinylogous formamides

Vinylogous formamides--5-formyluracils and 4-formylpyrazoles-undergo smooth olefination in THF in the presence of indium metal (0.8 equiv) and BF₃·OEt₂ (1 equiv) and allyl bromide (1 equiv) to provide the respective diene-substituted heterocycles in a single step     

The first application of 4-alkoxy-1,1,1-trifluoroalk-3-en-2-ones in a three-component condensation protocol for the synthesis of 3-acyl-4-aryl-2-(trifluoromethyl)-2-hydroxy-3,4,7,8-tetrahydro-2H-chromen-5(6H)-ones

The one-pot, simple and efficient three-component condensation protocol for the preparation of a series of twenty-five new 3-acyl-4-aryl-2-(trifluoromethyl)-2-hydroxy-3,4,7,8-tetrahydro-2H-chromen-5(6H)-ones, where aryl = Ph, 4-tolyl, 4-ClPh, 4-NO₂Ph and 4-CHOPh, and acyl = Ac, Bz, 4-FBz, furan-2-oyl, thien-2-oyl and naphth-1-oyl, employing 1,3-cyclohexanedione, five aryl aldehydes and for the first time, six 4-alkyl(aryl/heteroaryl)-4-methoxy-1,1,1-trifluoroalk-3-en-2-ones, is described. Yields in 15-75% were obtained when the MCRs were performed in the presence of a catalytic amount of triethylamine (25 mol%) and in ethanol as solvent under reflux for 16 h. A representative X-ray diffraction data for 3-acetyl-4-phenyl-2-(trifluoromethyl)-2-hydroxy-3,4,7,8-tetrahydro-2H-chromen-5(6H)-one is also showed.     

Selective extraction of thallium(III) in the presence of gallium(III), indium(III), bismuth(III) and antimony(III) by salting-out of an aqueous mixture of 2-propanol

Thallium(III), in the presence of other triply charged ions such as gallium, indium, bismuth and antimony in aqueous solution, was quantitatively and selectively extracted into 2-propanol/water phase by addition of NaCl ranging from 2.5 to 4.0 mol dm⁻³. The extraction efficiencies of gallium, indium, bismuth and antimony were much lower than that of thallium(III). Thus a maximal selective separation of thallium(III) from these elements could be attained using a 2-propanol/water mixture. Thallium(III) was extracted as TlCl₄⁻ with Na⁺. The detailed extraction mechanism in the presence of chloride, water in the organic phase and counter ions is discussed.     

1-(2′-Pyridylazo)-2-naphtholate (PAN) complexes of rhodium(III): Synthesis,structure and spectral studies

The ligating properties 1-(2′-pyridylazo)-2-naphthol (HPAN) toward Rh(III) have been examined. The reaction of RhCl₃·3H₂O with HPAN in presence of excess PPh₃ afforded trans-[Rh(PAN)Cl(PPh₃)₂]PF₆ (3PF₆). Intermediate cis-[Rh(PAN)Cl₂(PPh₃)] (4) has also been isolated. Solid state structures were authenticated by X-ray analyses revealing that monoanionic PAN is coordinated to rhodium in meridional fashion. Both the compounds were spectroscopically characterized in both solution and solid states, which include IR, NMR (¹H and ³¹P), and optical spectra. The diamagnetic complexes show multiple CT transitions in the visible region. Low-energy transitions (λ ≈ 550–650 nm) occurred in the absorption spectra are predominantly ligand centered in nature. The rhodium(III)–PAN compounds are red emissive (λ_em ≈ 650 nm) at room temperature and the nature of the emission level is probably an ILCT level. Complexes are electro-active in acetonitrile and display irreversible oxidative and reductive waves and these responses are ascribed to be PAN ligand centered in character.     

Two bis-[1-(aryliminomethyleny)-2-oxy-naphthalen] nickel catalysts for the polymerization of methyl methacrylate

Two bis-(1-arylliminomethylenyl-2-oxy-naphthalen) nickel complexes (aryl = 2-methylphenyl, complex 1; aryl = 2,6-diisoproylphenyl, complex 2) were reacted with alkylaluminium in presence of equimolar PPh₃ and tested as catalysts in methyl methacrylate (MMA) polymerization. The two nickel catalysts can initiate polymerization of MMA with good to high activity, the highest activity reaching 1.1 × 10⁵ g PMMA/(mol Ni · h) by less bulky complex 1 at 0.8 mol/L of MMA, 400 of Al/Ni ratio and 0 °C. In addition, the structures of nickel complexes and polymerization conditions, such as monomer concentration, polymerization temperature and Al/Ni molar ratio on catalytic activity of polymerization have great influences on catalytic activity and product properties.     

Calorimetric determination of enthalpy changes for proton ionization of N-[2-hydroxyethyl]piperazine-N′-[2-ethane sulfonic acid] (HEPES) and N-[2-hydroxyethyl]piperazine-N′-[2-hydroxypropane sulfonic acid] (HEPPSO) in water-methanol mixtures

Enthalpies for the two proton ionizations of the biochemical buffers N-[2-hydroxyethyl]piperazine-N′-[2-ethane sulfonic acid] (HEPES) and N-[2-hydroxyethyl]piperazine-N′-[2-hydroxypropane sulfonic acid] (HEPPSO) were obtained in water-methanol mixtures with methanol mole fraction (X_m) from 0 to 0.360. With increasing methanol, the ionization enthalpy for the first proton (ΔH₁) of HEPES increased steadily from 8.4 to 15.3 kJ mol⁻¹ whereas that for HEPPSO rose to a maximum of 21.0 kJ mol⁻¹ at X_m = 0.123 before dropping to 18.4 kJ mol⁻¹ at X_m = 0.360. The ionization enthalpy for the second proton (ΔH₂) of HEPES varied from 20.8 kJ mol⁻¹ in water to 13.6 kJ mol⁻¹ at X_m = 0.360 with a maximum of 24.8 kJ mol⁻¹ at X_m = 0.194. For HEPPSO, ΔH₂ increased steadily from 23.4 to 29.2 kJ mol⁻¹. The solvent composition was selected so as to include the region of maximum structure enhancement of water by methanol. The results were interpreted in terms of solvent-solvent and solvent-solute interactions.     

Group 12 metal aryl selenolates. Crystal and molecular structure of [2-(Et2NCH2)C6H4]2Se2 and [2-(Me2NCH2)C6H4Se]2M (M = Zn, Cd)

Diorganodiselenide [2-(Et₂NCH₂)C₆H₄]₂Se₂ (1) was obtained by hydrolysis/oxidation of the corresponding [2-(Et₂NCH₂)C₆H₄]SeLi derivative. The treatment of [2-(Et₂NCH₂)C₆H₄]₂Se₂ with elemental sodium in THF resulted in [2-(Et₂NCH₂)C₆H₄]SeNa (2). Reactions between alkali metal selenolates [2-(R₂NCH₂)C₆H₄]SeM′ (R = Me, Et; M′ = Li, Na) and MCl₂ (M = Zn, Cd) in a 2:1 molar ratio resulted in the [2-(R₂NCH₂)C₆H₄Se]₂M species [R = Me, M = Zn (3), Cd (4); R = Et, M = Zn (5), Cd (6)]. The new compounds were characterized by multinuclear NMR (¹H, ¹³C, ⁷⁷Se, ¹¹³Cd) and mass spectrometry. The crystal and molecular structures of 1, 3 and 4 revealed monomeric species stabilized by N → Se (for 1) and N → M (for 3 and 4) intramolecular interactions.     

Catalytic transfer hydrogenation of ketones catalyzed by orthometalated ruthenium(III) 2-(arylazo)phenolate complexes containing triphenylarsine

Air-stable, mononuclear orthometalated ruthenium(III) 2-(arylazo)phenolate complexes of the general composition [RuX(AsPh₃)₂(L)] (X = Cl or Br; L = CNO donor of the 2-(arylazo)phenolate ligands) have been synthesized and characterized by IR, UV-vis, and EPR as well as by elemental analysis. One of the complexes [RuBr(AsPh₃)₂(azo-OMe)] was structurally characterized by X-ray analysis and was found to be an efficient catalyst for the transfer hydrogenation of ketones with excellent conversion in the presence of isopropanol at 80 °C in 1 h.     

Reactivity studies of cyclopentadienyl ruthenium(II), osmium(II) and pentamethylcyclopentadienyl iridium(III) complexes towards 2-(2′-pyridyl)imidazole derivatives

The reaction of [CpRu(PPh₃)₂Cl] and [CpOs(PPh₃)₂Br] with chelating 2-(2′-pyridyl)imidazole (N ∩ N) ligands and NH₄PF₆ yields cationic complexes of the type [CpM(N ∩ N)(PPh₃)]⁺ (1: M = Ru, N ∩ N = 2-(2′-pyridyl)imidazole; 2: M = Ru, N ∩ N = 2-(2′-pyridyl)benzimidazole; 3: M = Ru, N ∩ N = 2-(2′-pyridyl)-4,5-dimethylimidazole; 4: M = Ru, N ∩ N = 2-(2′-pyridyl)-4,5-diphenylimidazole; 5: M = Os, N ∩ N = 2-(2′-pyridyl)imidazole; 6: M = Os, N ∩ N = 2-(2′-pyridyl)benzimidazole). They have been isolated and characterized as their hexafluorophosphate salts. Similarly, in the presence of NH₄PF₆, [Cp∗Ir(μ-Cl)Cl]₂ reacts in dry methanol with N ∩ N chelating ligands to afford in excellent yield [Cp∗Ir(N ∩ N)Cl]PF₆ (7: N ∩ N = 2-(2′-pyridyl)imidazole; 8: N ∩ N = 2-(2′-pyridyl)benzimidazole). All the compounds have been characterized by infrared and NMR spectroscopy and the molecular structure of [1]PF₆, [2]PF₆ and [7]PF₆ by single-crystal X-ray structure analysis.     

Swelling behaviour of crosslinked hydrogels based on (2-hydroxyethyl methacrylate) with a zwitterionic comonomer (1-3-sulfopropyl-2-vinyl-pyridinium-betaine)

Copolymeric hydrogels were prepared by the chemically initiated free radical copolymerization in aqueous solution of mixtures of [1-(3-sulfopropyl)-2-vinyl-pyridinium-betaine] (SPV) and (2-hydroxyethyl methacrylate) (HEMA) in the presence of a crosslinking agent N,N′-methylene-bis-acrylamide (MBA). The hydrogels were swollen to equilibrium in water and aqueous KSCN at 298 K and their swelling behaviour has been investigated using gravimetric measurements. The effects of the concentration of KSCN and the mole fraction of SPV in the feed (F_s) have been noted and discussed. The main findings are:(a) In water, the water content (W₁) of copolymeric hydrogels is insensitive to SPV content at F_s ? 0.45. In contrast, W₁ decreases sharply with decreasing F_s within the range of 0 < F_s < 0.45. (b) In aq. KSCN, the degree of total swelling (W) exceeds the value in pure water, the enhancement in swelling being most marked at low values of [KSCN]. The content of water within the hydrogel increases with KSCN concentration in the swelling medium for low values of [KSCN], but thereafter falls with further increase in salt concentration. In contrast, the salt content within the swollen hydrogel displays a continuous increase with increasing [KSCN]. All these results of item (b) are for copolymeric hydrogels within the full range of F_s (0 < F_s < 1). (c) at a fixed aq. KSCN concentration, both W and W₁ increase sharply with increasing F_s over the entire range of copolymer composition.     

Nitro group photoreduction of 4-(2-nitrophenyl)- and 4-(3-nitrophenyl)-1,4-dihydropyridines

The photoprocesses of nifedipine, a 4-(2-nitrophenyl)-1,4-dihydropyridine, and nimodipine and nitrendipine, two 3-nitrophenyl Hantzsch-type analogues, were studied by steady-state and time-resolved methods. The intramolecular photoreduction of nifedipine into its nitrosophenyl product takes place within a few ns. The quantum yield of conversion is Φ_red = 0.3 and does not depend significantly on the oxygen concentration and solvent properties. Formation of the fully reduced 4-(2-aminophenyl)-1,4-dihydropyridine as minor product is indicated by fluorescence spectroscopy. The photoreduction of nimodipine and nitrendipine is inefficient, Φ_red = 0.002 in acetonitrile, but markedly enhanced in the presence of donors such as triethylamine (TEA) and 2-propanol, e.g. for TEA Φ_red is up to 0.03. The triplet states of nimodipine and nitrendipine were characterized. They react intermolecularly with TEA and 2-propanol, forming radicals as intermediates and eventually several reduction products.     

1-(2′-Pyridylazo)-2-naphtholate complexes of ruthenium: Synthesis,characterization, and DNA binding properties

Reaction of 1-(2′-pyridylazo)-2-naphthol (Hpan) with [Ru(dmso)₄Cl₂] (dmso = dimethylsulfoxide), [Ru(trpy)Cl₃] (trpy = 2,2′,2″-terpyridine), [Ru(bpy)Cl₃] (bpy = 2,2′-bipyridine) and [Ru(PPh₃)₃Cl₂] in refluxing ethanol in the presence of a base (NEt₃) affords, respectively, the [Ru(pan)₂], [Ru(trpy)(pan)]⁺ (isolated as perchlorate salt), [Ru(bpy)(pan)Cl] and [Ru(PPh₃)₂(pan)Cl] complexes. Structures of these four complexes have been determined by X-ray crystallography. In each of these complexes, the pan ligand is coordinated to the metal center as a monoanionic tridentate N,N,O-donor. Reaction of the [Ru(bpy)(pan)Cl] complex with pyridine (py) and 4-picoline (pic) in the presence of silver ion has yielded the [Ru(bpy)(pan)(py)]⁺ and [Ru(bpy)(pan)(pic)]⁺ complexes (isolated as perchlorate salts), respectively. All the complexes are diamagnetic (low-spin d⁶, S = 0) and show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on all the complexes shows a Ru(II)–Ru(III) oxidation on the positive side of SCE. Except in the [Ru(pan)₂] complex, a second oxidative response has been observed in the other five complexes. Reductions of the coordinated ligands have also been observed on the negative side of SCE. The [Ru(trpy)(pan)]ClO₄, [Ru(bpy)(pan)(py)]ClO₄ and [Ru(bpy)(pan)(pic)]ClO₄ complexes have been observed to bind to DNA, but they have not been able to cleave super-coiled DNA on UV irradiation.     

3-(o-Trifluoroacetamidoaryl)-1-propargylic esters: common intermediates for the palladium-catalyzed synthesis of 2-aminomethyl-, 2-vinylic, and 2-alkylindoles

3-(o-Trifluoroacetamidoaryl)-1-propargylic esters have been used as common synthetic intermediates for the preparation of a variety of 3-unsubstituted 2-substituted indoles. Treating ethyl 3-(o-trifluoroacetamidoaryl)-1-propargylic carbonates unsubstituted or containing an aryl substituent at the propargylic carbon with piperazines and Pd(PPh₃)₄ in THF at 80 °C affords 2-(piperazin-1-ylmethyl)indoles in excellent yields. Good to excellent yields of 2-aminomethylindoles are also obtained with other secondary amines. Ethyl 3-(o-trifluoroacetamidoaryl)-1-propargylic carbonates bearing an alkyl substituent at the propargylic carbon and ethyl 3-(o-trifluoroacetamidoaryl)-1-propargylic acetates disubstituted at the propargylic carbon give 2-vinylic indoles with the Pd(OAc)₂/PPh₃ combination and Et₃N in THF at 80 °C. Formation of 2-vinylic indoles is quite stereoselective, generating trans vinylic derivatives, at least with the substrates that we have investigated. In the presence of formic acid, Et₃N, and Pd(PPh₃)₄ in MeCN at 80 °C, ethyl 3-(o-trifluoroacetamidoaryl)-1-propargylic carbonates afford 2-alkylindoles in good to excellent yields.     

Titanium (IV) complexes based on substituted 2-[(2-hydroxyethyl)]aminophenols

Novel substituted 2-[(2-hydroxyethyl)]aminophenols, MeN(CHR¹CR²R³OH)(C₆H₄-o-OH) (2-5), were synthesized by the reaction of 2-methylaminophenol with corresponding oxiranes. Titano-spiro-bis(ocanes) [MeN(CHR¹CR²R³O)(C₆H₄-o-O)]₂Ti 6-9 (2, 6, R¹ = H, R² = R³ = Me; 3, 7, R¹ = R² = Ph (treo-), R³ = H; 4, 8, R¹ = Ph, R² = R³ = H; 5, 9, R¹ = R² = H, R³ = Ph) based on [ONO]-ligands have been synthesized. The obtained compounds were characterized by ¹H and ¹³C NMR spectroscopy and elemental analysis data. The complex [Ti(μ²-O){O-o-C₆H₄}{μ²-CMe₂CH₂}NMe]₆ (10) was obtained by controlled hydrolysis of 6. Molecular structure of 10 was determined by X-ray structure analysis.