Energy of the Photosubstitutionally Reactive Excited State of Pentaammine(pyridine)ruthenium(II)

The photosensitized aquation of pentaammine(pyridine)ruthenium(II) by several dyes has been studied under conditions where only the sensitizers absorb light. The ratio of the quantum yields for ammine and pyridine substitution was the same as that for direct photoaquation. Sensitization was effective with singlet sensitizers Rhodamine-B (17 452 cm -1) and Safranine-T (17 690 cm -1), as well as the triplet sensitizer biacetyl (19 000 cm -1), but no reaction was observed with Neutral-Red (16 900 cm -1). The results indicate that the excited state precursor of the observed photosubstitution in the complex lies in the energy range between 17 000 and 17 700 cm -1.

SAXS measurements of the porosity in Cu(II)-doped SnO2 xerogels during crystallization

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Structure of cobalt (II) perchlorate adsorbed on silica gel surface chemically modified with benzimidazole molecule

Covalently attached benzimidazole molecules on silica gel surface, ≡SiL (where L = N-propyl-benzimidazole), adsorbs Co(ClO4)2 from non-aqueous solvent by forming a surface complex according to the reaction: m ≡SiL + Co(ClO4)2 → (≡SiL)mCo(ClO4)2. The equilibrium constant and the adsorption capacity, determined by applying the Langmuir equation were b = 3.0 × 103 L mol-1 and Ns= 0.098 × 10-3 mol g-1, respectively. The metal is bonded through the nitrogen atom and the perchlorate ion is not coordinated. The ESR study indicated that the complex has essentially an octahedral geometry with tetragonal distortion, with the electrons of the four nitrogen atoms interacting with the cobalt central metal ion in the equatorial plane. Only one complex species was detected on the surface.

Factor V Leiden and factor II G20210A mutations in patients with recurrent abortion

Recurrent abortion (RA) represents an intriguing problem in obstetric practice in which genetic and acquired factors may play a role. In the present investigation we sought to assess the possibility that inherited thrombophilia might determine the risk of RA. We therefore investigated the prevalence of two genetic abnormalities frequently associated with venous thrombosis [factor V Leiden (FVL) and factor II G20210A] in 56 patients with primary or secondary abortion and in 384 healthy control women. Polymerase chain reaction amplification followed by digestion with the restriction enzymes MnlI and HindIII was used to define the FVL and FII G20210A genotypes respectively. FVL was found in 4/56 patients (7.1%) and in 6/384 controls (1.6%), yielding an odds ratio (OR) for RA related to FVL of 4.9 [95% confidence interval (CI): 1.3-17.8]. FII G20210A was detected in 2/56 (3.6%) patients and in 4/384 (1%) controls (OR for RA: 3.5, CI: 0.6-19.7). In conclusion, FVL and FII G20210A mutations in patients with RA were more prevalent in comparison with controls. These data support a role for both mutations as determinants of the risk of RA and strengthen the notion that thrombophilia plays a role in this clinical entity.

Crystallographic and spectroscopic studies on palladium(II) complexes containing pyrazole and thiocyanate ligands

Mononuclear palladium(II) complexes containing both pyrazole-type ligands and thiocyanate, of general formula [Pd(SCN) 2(L) 2] {L = pyrazole (HPz) and l-phenyl-3-methylpyrazole (phmPz)} have been prepared and characterized by elemental analysis, i.r. and n.m.r. spectroscopy and by single crystal X-ray diffraction methods. The Pd atom in these structures lies on the crystallographic inversion center; in a square-planar coordination geometry made by two sulfur and two nitrogen atoms of the ligands, both in trans positions.

Preconcentration and determination of mercury(II) at a chemically modified electrode containing 3-(2-thioimidazolyl)propyl silica gel

A mercury-sensitive chemically modified graphite paste electrode was constructed by incorporating modified silica gel into a conventional graphite paste electrode. The functional group attached to the (3-chloropropyl) silica gel surface was 2-mercaptoimidazole, giving a new product denoted by 3-(2-thioimidazolyl)propyl silica gel, which is able to complex mercury ions. Mercury was chemically adsorbed on the modified graphite paste electrode containing 3-(2-thioimidazolyl)propyl silica (TIPSG GPE) by immersion in a Hg(II) solution, and the resultant surface was characterized by cyclic and differential pulse anodic stripping voltammetry. One cathodic peak at 0.1 V and other anodic peak at 0.34 V were observed on scanning the potential from -0.1 to 0.8 V (0.01 M KNO3; ν = 2.0 mV s-1 νs. Ag/AgCl). The anodic peak at 0.34 V show an excellent sensitivity for Hg(II) ions in the presence of several foreign ions. A calibration graph covering the concentration range from 0.02 to 2 mg L-1 was obtained. The detection limit was estimated to be 5 μg L-1. The precision for six determinations of 0.05 and 0.26 mg L-1 Hg(II) was 3.0 and 2.5% (relative standard deviation), respectively. The method can be used to determine the concentration of mercury(II) in natural waters contaminated by this metal. 2005 © The Japan Society for Analytical Chemistry.

Hydrothermal synthesis and crystal structure of a copper(ii) coordination polymer with bridging dicarboxylate and diamine ligands

This work reports on the synthesis of a copper(II) coordination compound with 4,4-oxibis(benzoate) (obb) and trans-1,2- bis(4-pyridyl)ethene (bpe) ligands. The complex was characterized by single-crystal X-ray diffraction, which showed a 3D polymeric structure. Each copper center is surrounded by four oxygen atoms at the basal plane and one nitrogen atom and one copper atom at the axial positions, revealing a distorted octahedral geometry. Four carboxylic groups bridge two copper atoms, forming a cage-like structure, with the distance between the metallic centers being 2.656(1)Å. 2008 © The Japan Society for Analytical Chemistry.

Crystal and molecular structure of dinuclear palladium(II) complex containing nitrogen and phosphorus donor ligands, [Pd2(N3)4(PPh3)2(μ-ted)]

The dinuclear azido-palladium(II) complex [Pd2(N3)4(PPh3)2(μ-ted)], where PPh3 = triphenylphosphine and ted = triethylenediamine, was synthesized and characterized by single-crystal X-ray diffraction. The title compound was crystallized in a triclinic system, space group P1 with a = 11.5875(2)Å, b = 13.0817(3)Å, c = 15.2618(3)Å, α = 93.306(2)°, β =110.040(1)°, γ = 98.486(1)°, V = 2134.95(8)Å3, Z = 2. Each Pd(II) center displays a distorted squareplanar coordination environment formed by two N atoms from two trans terminally coordinated azido groups, one P atom from the phosphine and one N atom from the bridging ted ligand. 2008 © The Japan Society for Analytical Chemistry.

Molecular and crystal structure of Di(μ-N,S-thiocyanato)-bis[(N,N-dimethylbenzylamine-C2, N)palladium(II)]

The cyclopalladated complex [Pd(C2,N-dmba)(μ-SCN)]2, where dmba = N,N-dimethylbenzylamine, was structurally characterized by single-crystal X-ray diffraction. This compound crystallizes in the monoclinic system, space group P21/n with a = 9.578(1)Å, b = 12.323(2)Å, c = 10.279(2)Å, β = 117.03(1)°, V = 1080.7(3)Å3, Z = 2. Each Pd(II) center displays a distorted square-planar coordination environment, formed by the C and N atoms from the dmba ligand, and one set of N and S atoms from the bridging SCN groups. 2009 © The Japan Society for Analytical Chemistry.

Study of the electrochemical behavior of histamine using a Nafion®-copper (II) hexacyanoferrate film-modified electrode

A study on the electrochemical behavior of histamine species in aqueous medium is described. A glassy carbon electrode chemically modified with copper (II) hexacyanoferrate (CuHCFe) film and covered with Nafion® film was employed. The interaction between the analyte and the CuHCFe film can be demonstrated by a decrease in both the cathodic and anodic peak currents at 0.68V (vs. Ag/AgCl), attributed to the film and the appearance of new peak current at 0.47V. Cyclic voltammetric parameters obtained for histamine indicate the formation of stable complex between histamine adsorbed at the electrode surface. The dependence of peak currents on the concentration of the analyte is not linear in the employed work range, indicating the presence of a coupled chemical reaction in the electrodic process. © 2010 by ESG.

Concentration of Cu(II) and Cd(II) from natural river water by Adsorption on a Modified Silica Surface

A high surface area silica gel (737 ± m2 g-1) was synthesized modified through a two-step reaction with a 4-amino-2-mercaptopyrimidine ligand and applied to Cu(II) and Cd(II) adsorption from an aqueous medium. The modified material was characterized by FTIR, which showed that attachment of the molecule occurred via thiol groups at 2547 and 2600 cm-1, and by elemental analysis that indicated the presence of 0.0102 mmol of ligand. The data from adsorption experiments were adjusted to a modified Langmuir equation and the maximum adsorption capacity was 6.6 and 3.8 μmol g-1 for Cu(II) and Cd(II), respectively. After adjusting several parameters, the material was applied in the preconcentration of natural river water using a continuous flow system before and after sample mineralization, and the results showed a 10-fold enrichment factor. The proposed method was validated through preconcentration and analysis of certified standard reference material (1643e), whose results were in agreement with the values provided by the manufacturer.

Voltammetric Study of a Cubic Silsesquioxane Organically Modified with Imidazole and their Subsequent Reaction with Cadmium and Hexacyanoferrate (III)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dba-free palladium intermediates of the Heck-Matsuda reaction

The dba-free Heck-Matsuda reaction was investigated via direct ESI-MS(/MS) monitoring. Palladium species involved in the reduction of Pd(ii) during a Wacker type reaction and several dba-free arylpalladium transient complexes were detected and characterized. Based on these findings, a more comprehensible catalytic cycle for this pivotal reaction is suggested. © 2013 The Royal Society of Chemistry.

Synthesis, cytotoxic activity and DNA interaction of Pd(II) complexes bearing N′-methyl-3,5-dimethyl-1-thiocarbamoylpyrazole

A new series of complexes of general formulae [PdX2(tmdmPz)] {X = Cl (1), Br (2), I (3), SCN (4); tmdmPz = N′-methyl-3,5-dimethyl-1- thiocarbamoylpyrazole} have been synthesized and characterized by elemental analysis, molar conductivities, IR, 1H and 13C{ 1H} NMR spectroscopy. In these complexes, the tmdmPz coordinates to Pd(II) center as a neutral N,S-chelating ligand. The geometries of the complexes have been optimized with the DFT method. Cytotoxicity evaluation against LM3 (mammary adenocarcinoma) and LP07 (lung adenocarcinoma) cell lines indicated that complexes 1-4 were more active than cisplatin. The binding of the complexes with a purine base (guanosine) was investigated by 1H NMR and mass spectrometry, showing that the coordination of guanosine occurs through N7. Electrophoretic DNA migration studies showed that all of them modify the DNA tertiary structure. © 2013 Elsevier Ltd. All rights reserved.

Development of a thermoeconomic methodology for optimizing biodiesel production. Part II: Manufacture exergetic cost and biodiesel production cost incorporating carbon credits, a Brazilian case study

The purpose of this study is to carry on a thermoeconomic analysis at a biodiesel production plant considering the irreversibilities in each step (part I: biodiesel plant under study and functional thermoeconomic diagram [1]), making it possible to calculate the thermoeconomic cost in US$/kWh and US$/l of the biodiesel production, and the main byproduct generated, glycerin, incorporating the credits for the CO2 that is not emitted into the atmosphere (carbon credits). Assuming a sale price for both the biodiesel and the byproduct (glycerin), the annual revenue of the total investment in a plant with a capacity of 8000 t/year of biodiesel operating at 8000 h/year was calculated. The variables that directly or indirectly influence the final thermoeconomic cost include total annual biodiesel production, hours of operation, manufacturing exergy cost, molar ratio in the transesterification reaction, reaction temperature and pressure in the process. Depending on the increase or decrease in sale prices for both biodiesel and glycerin, the payback is going to significantly increase or decrease. It is evident that, in exergy terms, the sale of glycerin is of vital importance in order to reduce the biodiesel price, getting a shorter payback period for the plant under study. © 2013 Elsevier Ltd. All rights reserved.