2–Hydroxy–1,3–propylene bis (oxamato)–bridged new NiIICuIINiII trinuclear complexes with an S = 3/2 high-spin ground state: synthesis and magnetism

Four new heterotrinuclear complexes have been synthesized and characterized, namely {[Ni(L)2]2[Cu(pbaOH)]}(ClO4)2, where pbaOH denotes 2–hydroxy–1,3–propylenebis(oxamato) and L = 1,10–phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO2–phen), 2,2–bipyridyl (bpy) and 4,4–dimethyl–2,2–bipyridyl (Me2bpy). The temperature dependence of the magnetic susceptibility of {[Ni(phen)2]2[Cu(pbaOH ]}(ClO4)2·H2O has been studied in the 4–300 K range, giving an exchange integral J = –94 cm– . The MT versus T plot exhibits a minimum at ca. 93 K, characteristic of this type of coupled polymetallic complex with an irregular spin-state structure.     

Accumulation and distribution of elements in rice /seed,brand layer,husk/ by neutron activation analysis

Various rice samples /seed, brand layer, husk/ from Vietnam were analyzed for Se, Hg, Cr, Ni, Sc, Rb, Fe, Zn and Co by neutron activation analysis. The concentration values found /seed/ were the following: Se 0.04–0.07 ppm, Hg 0.02–0.07 ppm, Cr 2.13–8.65 ppm, Ni 1.56–4.95 ppm, Sc 0.02–0.06 ppm, Rb 0.84–2.71 ppm, Fe 26.31–96.07 ppm, Zn 10.65–27.39 ppm and Co 0.02–0.15 ppm. The values were reported in ppm /dry weight/. Statistical analysis /t-test, t=0.05/ showed that the content of elements varies between sorts of rice; the content of Rb, Fe, Ni, Cr of rice husk was significantly higher than in rice seed and brand layer.     

Structure Development in Simple Cross-Linked Organopolysiloxanes

13C CP and CPPI MAS NMR have been carried out on thermally cured samples of polymethylvinylsiloxane and polydimethylsiloxane. By varying the CP contact time, the and vinyl carbons and the methyl carbon of the CH3–(SiO<)–CH=CH2 species could be identified. A further methyl carbon was detected which was less mobile and which we assign to methyl groups attached to silicon species on which the vinyl group has reacted to form a cross-link. Resonance from – CH2– carbons was observed in the 30–40 ppm range, and these species arise from methyl-vinyl cross-linking to give CH3–(SiO<)– H2– H2–(SiO<)–CH=CH2. Higher temperature curing promotes vinyl-vinyl cross-linking to give CH3–(SiO<)–CH2– H–CH2–(SiO<)–CH3 links between chains. Evidence for this comes from the insensitivity of the carbon resonance under CPPI, indicating that it is in a – CH= rather than a =CH2 environment. There was also evidence of –CH2– carbons in the polydimethylsiloxane material, suggesting that thermally activated, methyl-methyl cross-linking can occur to give CH3–(SiO<)– H2– H2(SiO<)–CH3 links between chains.     

Catechins and proanthocyanidins ofAlhagi sparsifolia. I

Ten individual compounds have been isolated from the epigeal part ofAlhagi sparsifolia Shap. in various stages of vegetative growth. Their structures have been established by a study of PMR spectra, physicochemical properties, and the products of chemical transformations: (–)-epicatechin, (–)-epigallocatechin, (–)-epigallocatechin gallate, (+)-catechin, (+)-gallocatechin, proanthocyanidin B-2, (–)-epigallocatechin-(4–8)-(–)-epicatechin, epigallocatechin gallate-(4–8)-(–)-epicatechin, proanthocyanidin B-1, and (–)-epicatechin-(4–8)-gallocatechin.The materials of this paper were presented at the Second International Symposium on the Chemistry of Natural Compounds (SCNC, Eskiehir, Turkey, October 22–24, 1996).Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 232–237, March–April, 1997.     

Group additivity for the standard partial molal heat capacities and volumes of polar compounds in methanol at 25°C

A flow heat capcity calorimeter and a flow vibrating tube densimeter have been used to measure the apparent molal heat capacities and volumes of benzene and 25 polar compounds in methanol at 25°C. These quantities have been extrapolated to infinite dilution to obtain the standard partial molal heat capacities and volumes. The and data have been used in conjunction with an additivity scheme previously determined for alkanes. Group contributions were evaluatd for –OH, –NH₂, –COOH, –C₆H₅, C=O, –COO–, –CONH–, –O–, –S–, and –S₂–. The concentration dependences of _cp and _v of nonelectrolytes in methanol are qualitatively similar but much smaller than in water.     

Determination of differences in free and bound water contents of beef muscle by DSC under various freezing conditions

The differences in bound water content of beef semimembranous muscle samples obtained from previously chilled (24 h at +4°C) middle-aged beef carcasses were determined by the use of DSC. Initially, samples obtained from fresh, unprocessed meat were frozen at –40, –50 or –65°C to determine their melting peaks for freezable water (free water) content with the use of DSC. The samples were then subjected to an environment with an ambient temperature of –30, –35, –40 or –45°C, with no air circulation, or with an air circulation speed of 2 m s^–1, until a thermal core temperature of –18°C was attained; this was followed by thawing the samples until a thermal core temperature of 0°C was reached. This process was followed by subjecting the samples to the ambient temperatures mentioned above, to accomplish complete freezing and thawing of the samples, with DSC, and thereby determination of the freezable water contents, which were then used to determine the peaks of melting. The calculated peak areas were divided by the latent heat of melting for pure water, to determine the freezable water contents of the samples. The percentage freezable water content of each sample was determined by dividing its freezable water content by its total water content; and the bound water content of each sample was determined by subtracting the percentage free water content from the total. In view of the fact that the free water content of a sample is completely in the frozen phase at temperatures of –40°C and below, the calculations of free and bound water contents of the samples were based on the averages of values obtained at three different temperatures.     

Emission characteristics of high-powered microwave induced plasma optical emission spectrometry by using nitrogen–oxygen mixture gas

A high-powered, microwave-induced nitrogen–oxygen plasma (N₂–O₂–MIP) generated by using an Okamoto cavity at atmospheric pressure was investigated when the observation height, the flow rate of carrier gas, and the oxygen content were varied as the experimental parameters. The emission characteristics of the plasma were evaluated with regard to the excitation temperature and the intensity ratio of atomic line to ionic line. The excitation temperature of the N₂–O₂–MIP was in the range of 5100–5700 K when the oxygen content was varied from 0 to 30% at the observation height of 7 mm and the carrier gas flow rate of 0.6 l/min. The intensity ratio of atomic line to ionic line was elevated with an increase in the oxygen content.     

Essential oil ofPerovskia angustifolia from Kyrgyzystan

The water distilled essential oils from leaves ofPerovskia angustifolia (Labiatae) collected from three different localities in the Arslonbob mountains of Kyrgyzystan were analyzed by GC/MS. 1,8-Cineole (12.0–27.5%), -pinene (7.3–14.7%), epi-13-manool (3.8–12.6%) bornyl acetate (1.2–8.7%), camphene (2.5–6.8%), camphor (4.3–6.5%), -caryophyllene (3.2–6.5%), caryophyllene oxide (1.7–5.9%), -humulene (2.1–5.2%), humulene epoxide II (1.9–4.8%), caryophylladienol (1.4–4.3%), and borneol (3.0–3.2%) were found as major constituents.Materials presented at the 2nd International Conference of Natural Compounds.Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 386–388, May–June, 1997.     

The kinetics and mechanism of aquation and base hydrolysis of the cis-[Co(cyclen)Cl2]+ cation (cyclen=1,4,7,10-tetraazacyclododecane)

The aquation of cis-[Co(cyclen)Cl2]+ (cyclen=1,4,7,10-tetraazacyclododecane) has been studied over a range of temperatures with 0.1 mol dm–3 HNO3 as solvent. At 25°C, kaq=4.5×10–3 s–1 with H=78 kJ mol–1 and S298=–21 J K–1 mol–1. Base hydrolysis of cis-[Co(cyclen)Cl2]+ is extremely rapid with kOH=2.1×107 dm3 mol–1 s–1 at 25°C and I=0.1 mol dm–3. This is the largest rate constant so far reported for the base hydrolysis of a cis-dichloro-complex of a saturated macrocycle. The activation parameters, H=53 kJ mol–1 and S298=73 J K–1 mol–1 are consistent with a mechanism in which deprotonation of the substrate is rate-determining. This conclusion is confirmed by the observation of general base catalysis by formate ion. The Brønsted value for the reaction is ca. 0.72 and SN1(CB) and E2 mechanisms are considered to account for the kinetic results. Base hydrolysis of cis-[Co(cyclen)(OH)Cl]+ has also been studied in the pH range 6.5 to 8.7. The value of kOH=3.8×102 dm3 mol–1 s–1 at 25°C and I=0.1 mol dm–3 with H=110 kJ mol–1 and S298=171 J K–1 mol–1 are consistent with an SN1(CB) mechanism.     

Electrical Double Layer on Liquid Sn–Ga Alloy in Aqueous Solutions

Double-layer parameters of a liquid Sn–Ga electrode in aqueous electrolyte solutions are studied. It is shown that Sn in the alloy with Ga is a surface-active component and is forced out onto a surface layer of the electrode. The double-layer parameters of an Sn–Ga electrode (8 at. % Sn), which are measured in the experimentally accessible range of charges, differ radically from the parameters of Ga electrodes and are close to those of Sn electrode. Hence, an Sn–Ga electrode containing 8 at. % Sn simulates electrochemical properties of a liquid Sn electrode. The difference between reciprocal electronic capacitances of Hg and Sn and a corrected electrochemical work function of Sn are determined. It is shown that the chemisorption interaction of an Sn–Ga electrode with water molecules is virtually absent at charges more negative than –7 C/cm². A potential drop on uncharged Sn, which is associated with water chemisorption, is –20 mV. Thus, the hydrophilicity of Sn is slightly higher than that of Hg, Bi–Ga, Pb–Ga, and Tl–Ga and significantly lower than that of In–Ga, Cd–Ga, and Ga.     

The mutual catalytic effect in kinetic reactions and its application to simultaneous determination of binary components

The mutual catalytic effect between iron(II) and antimony(III) on the chromium(VI)-iodide kinetic reactions has been studied by stopped-flow FIA. The concept of mutual catalytic coefficient is defined. The deviations from additive principles of absorbance within certain concentration ranges in previous procedures can be compensated effectively, by introducing the mutual catalytic coefficient into the simultaneous determination of a binary mixture with stopped-flow-FIA method. The linear concentration ranges have been enlarged, 0–3.5 g/ml Fe(II) and 0–3.7 g/ml Sb(III) compared with 0–1.2 g/ml Fe(II) and 0–2.0 g/ml Sb(III) without use of the coefficient. Iron and antimony contents in wastewater, a simulated sample and a zinc standard were determined, the recoveries and relative standard deviations being, respectively, 99.8–101.3% and 2.7–3.6% for iron and 95.4–100.3% and 2.3–5.3% for antimony compared with 95.2–98% and 3.0–4% for iron and 96–104% and 4.5–4.8% for antimony, assuming additivity.     

Formation constants and thermodynamic parameters of α-pyridoin thiosemicarbazones with divalent metal ions

The proton–ligand stability constants of -pyridoin thiosemicarbazone, -pyridoin 2–methylthiosemicarbazone, -pyridoin 4–methylthiosemicarbazone and -pyridoin (4–phenylthiosemicarbazone) as well as the formation constants of their chelates with CuII, NiII, CoII, ZnII and MnII have been determined. The Calvin–Bjerrum pH titration techniques, as modified by Irving and Rossotti, were employed in aqueous media at different ionic strengths and temperatures. The stability constants of the complexes follow the order: CuII > NiII > CoII > ZnII >MnII which is in accord with the Irving–Williams series. The chelates derived from -pyridoin 4–phenylthiosemicarbazone have relatively higher stability constants, which may be attributed to the presence of the benzene ring in the chain.     

Synthesis and characterization of some methyl complexes of palladium(II). Part 2(1)

Summary Dichloro complexes of Pd^II, [Pd(L–L)Cl₂], where L–L=1-(thiomethyl)-2-(diphenylarsino)ethane (S–As) or 1-(thiomethyl)-2-(diphenylphosphino)ethane (S–P) andtrans-[PdL₂Cl₂], where L=diphenyl(2-phenylethyl)-phosphine (PE), diphenyl(1-naphthyl)phosphine (PN) orN-methyl-2-thiophenealdimine (SN), have been prepared and characterized. The reactions of these complexes with MeLi were investigated. The dimethyl complexes [Pd(L–L)Me₂] (L–L=S–As, S–P) and [Pd(PE)Me₂] were isolated and characterized. Reaction of [Pd(L–L)Me₂] (L–L=S–As, S–P) with HCl affords the monomethyl derivatives [Pd(L–L)Me(Cl)]. In contrast to the Pt analogues, [Pd(L–L)Me₂] and [Pd(L–L)Me(Cl)] are relatively less stable than [Pt(L–L)Me₂] and [Pt(L–L)Me(Cl)].     

Proanthocyanidins ofZiziphus jujuba

The catechin and proanthocyanidin compositions of the leaves and bark ofZiziphus jujuba have been studied over the vegetation periods. This has led to the isolation of 16 compounds, including 8 monomeric catechins — (–)-epiafzelechin, (–)-epicatechin, (–)-epigallocatechin, (–)-epicatechin gallate, (–)-epigal-locatechin gallate, (+)-catechin, (+)-catechin gallate, and (+)-gallocatechin; 4 dimeric proanthocyanidins — (–)-epiafzelechin-(4-8)-(–)-epicatechin, proanthocyanidin B-2, (–)-epicatechin-(4-8)-(–)-epigallocatechin, and (–)-epiafzelechin-(4-8)-(–)-epigallocatechin; and 4 oligomeric proanthocyanidins consisting of epiafzelechin, epigallocatechin, catechin, and epicatechin with different degrees of polymerization. Their structures have been established by a study of PMR and¹³C NMR spectra and the products of chemical transformation.The materials of this paper were presented at the Second International Symposium on the Chemistry of Natural Compounds (SCNC, Eskiehir, Turkey, October 22–24, 1996).Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 221–231, March–April, 1997.     

Theoretical Study of Chemical Binding of Noble Gas Atom and Transition Metal Complexes: Ng–NiCO, Ng–NiN2, Ng–CoCO (Ng = He–Xe)

Ab initio multireference and coupled cluster methods (MR-SDCI(+Q), CASPT2, CCSD(T)) and density functional theory methods (B3LYP, MPWPW91) have been applied to examine geometrical structures and vibrational frequencies of noble gas (Ng) – transition metal compounds, Ng–NiCO, Ng–NiN₂, and Ng–CoCO (Ng = He, Ne, Ar, Kr, Xe). It is shown that the respective compounds can have a larger binding energy than a typical van der Waals interaction energy. The binding mechanism is explained by a partial electron transfer from a noble gas atom to the low-lying 4s and 3d vacant orbitals of the transition metal atom. Theoretical calculations show that the binding of noble gas atom results in a large shift of the bending frequency: 361.1cm^–1 (NiCO) to 403.5cm^–1 (Ar–NiCO); 308.5cm^–1 (NiN₂) to 354.8cm^–1 (Ar–NiN₂); 373.0cm^–1 (CoCO) to 422.6cm^–1 (Ar–CoCO). The corresponding experimental frequencies determined in solid argon are 409.1cm^–1 (NiCO), 357.0cm^–1 (NiN₂), and 424.9cm^–1 (CoCO), which are much closer to the corresponding frequency of Ar–NiCO, Ar–NiN₂, and Ar–CoCO, respectively.     

Formation and characterization of mixed polyelectrolyte–surfactant Langmuir layer templates for silver nanoparticle growth

The hydrophilic characteristic of the polyelectrolyte, poly(4-styrenesulfonic acid) (PSS), was modified by associating with the surfactant, dodecyltrimethylammonium bromide (DTMAB), to form polyelectrolyte–surfactant (PSS–DTMA) Langmuir layers at air/liquid interfaces. The interfacial behavior of the PSS–DTMA complexes was investigated with the Langmuir trough technique. The mixed PSS–DTMA Langmuir layers were then used as the two-dimensional templates to incorporate with silver precursors from the subphase, and were transferred onto mica substrates with the Langmuir–Blodgett (LB) deposition technique. The silver nanoparticles were fabricated in the resulting LB films with UV irradiation, and the morphology of the silver nanoparticle structures was analyzed by atomic force microscopy (AFM). The results indicated that increasing the DTMA⁺ content in the mixed PSS–DTMA system would enhance the hydrophobic characteristic of the complexes and then form stable PSS–DTMA Langmuir layers at interfaces. In addition, by varying the DTMA⁺ content, one could adjust the charge density in the Langmuir layer templates and thus control the association behavior between the two-dimensional templates and the silver precursors in the subphases. The AFM images demonstrated that the formation of the silver nanoparticle structures in the UV-treated LB films could be regulated with the DTMA⁺ content in the Langmuir layer templates. It is inferred that the polyelectrolyte–surfactant template offers a potential of designing structures of polyelectrolyte–nanoparticle materials with a template-synthesis procedure.     

Platinum concentration in silicone breast implant material and capsular tissue by ICP-MS

Inductively coupled plasma-mass spectrometry (ICP-MS) was used to determine the concentration of platinum (Pt) in silicone breast implant gel (range, 0.26–48.90 g g^–1 Pt; n=15), elastomer (range, 3.05–28.78 g g^–1 Pt; n=7), double lumen (range, 5.79–125.27 g g^–1 Pt; n=7), foam (range, 5.79–8.36 g g^–1 Pt; n=2), and capsular tissue (range, 0.003–0.272 g g^–1 Pt; n=15). The results show that very high levels of Pt are present in the encasing elastomer, double lumen, and foam envelope materials. Silicone breast implants can be a source of significant Pt exposure for individuals with these implants.     

Oxidation of Methanol on Pt,Pt–Ru,and Pt–Ru–Mo Electrocatalysts Dispersed in Polyaniline: An in situ Infrared Reflectance Spectroscopy Study

The electrochemical oxidation of methanol was investigated on a Pt–Ru–Mo catalyst with an in situ infrared reflectance spectroscopy. The electrocatalysts were prepared by an electrochemical deposition and dispersed in a conducting three-dimensional matrix of polyaniline (PAni). We observed that CO₂ is produced from methanol oxidation at 350 mV vs. RHE on PAni/Pt–Ru–Mo, which is 100 mV less negative than on PAni/Pt–Ru and 200 mV less than on PAni/Pt. The results suggest that Pt–Ru–Mo is less sensitive to CO_ADS poisoning than Pt–Ru and much more sensitive than Pt. Large differences are observed concerning the average wavenumber of _ADS between Pt–Ru–Mo, Pt–Ru, and Pt.     

Theoretical Study of Chemical Binding of Noble Gas Atom and Transition Metal Complexes: Ng–NiCO, Ng–NiN2, Ng–CoCO (Ng = He–Xe)

Summary. Ab initio multireference and coupled cluster methods (MR-SDCI(+Q), CASPT2, CCSD(T)) and density functional theory methods (B3LYP, MPWPW91) have been applied to examine geometrical structures and vibrational frequencies of noble gas (Ng) – transition metal compounds, Ng–NiCO, Ng–NiN₂, and Ng–CoCO (Ng = He, Ne, Ar, Kr, Xe). It is shown that the respective compounds can have a larger binding energy than a typical van der Waals interaction energy. The binding mechanism is explained by a partial electron transfer from a noble gas atom to the low-lying 4s and 3d vacant orbitals of the transition metal atom. Theoretical calculations show that the binding of noble gas atom results in a large shift of the bending frequency: 361.1cm^–1 (NiCO) to 403.5cm^–1 (Ar–NiCO); 308.5cm^–1 (NiN₂) to 354.8cm^–1 (Ar–NiN₂); 373.0cm^–1 (CoCO) to 422.6cm^–1 (Ar–CoCO). The corresponding experimental frequencies determined in solid argon are 409.1cm^–1 (NiCO), 357.0cm^–1 (NiN₂), and 424.9cm^–1 (CoCO), which are much closer to the corresponding frequency of Ar–NiCO, Ar–NiN₂, and Ar–CoCO, respectively.     

Determination of rare earth elements in mineral raw materials and rare earth industry products by neutron activation analysis

To determine REE in mineral raw materials, high purity RE metals and their compounds, neutron activation analysis with extraction chromatographic REE separation has been developed. Combination of the developed RE extraction and separation procedures with subsequent -spectrometric analysis of the RE radionuclides allows to determine their content with the lower detection limit –10^–5–10^–8%. The relative standard deviation is 0.2–0.3.