Thermal behaviourof complexes of antipyrine derivatives Part III.

The thermal behaviour of the mixed-ligand complexes of cobalt(II) and copper(I) ions with antipyrine derivatives of 1,2-ethanediamine or piperazine (BAMP and TAMEN), with water and with 2-mercapto-benzothiazole (Hmbt) was investigated. The complexes contain 2-mercaptobenzothiazole (Hmbt, in the case of cobalt(II) ion) or dimercaptobenzothiazine (mbt–mbt, in the case of copper(I) ion) molecules as ligands and perchlorate (ClO₄^–) or thiocyanate (SCN – ) ion as counterion. By heating, water and ligands release the solid phase at lower temperature. At higher temperatures process of different organic reactions of ligands (e.g. polymerization, polycondensation) could be suggested to interpret the relative high final mass values.     

Study of transport processes in plants by radioabsorption and microradiographic methods

The passive transport processes in plants of²²Na⁺,¹³⁷Cs⁺,⁴⁵Ca²⁺,⁶⁵Zn²⁺,⁵⁹Fe³⁺ and³²PO ₄ ³⁻ ions and the plant-protecting agent “Saphidon (¹⁴C)” were studied by a radioabsorption method. The parameters of the passive transport processes of²¹²Pb²⁺, borate and tetraborate ions in plants were measured by quantitative microradiographic methods, using photoemulsion and solid state nuclear track detectors. Ion diffusion concentration profiles within the plants were determined at various diffusion times and temperatures. The equation of linear diffusion combined with convection was used to determine the diffusion coefficients characteristic of the transport processes.     

Colour pigments of Trichoderma harzianum. Preliminary investigations with thin-layer chromatography-Fourier transform infrared spectroscopy and high-performance liquid chromatography with diode array and mass spectrometric detection

The colour pigments of Trichoderma harzianum fermentation broth were separated and the main fractions were tentatively identified by reversed-phase thin-layer chromatography-Fourier transform infrared spectroscopy (RP-TLC-FT-IR), RP-HPLC-diode array detection and RP-HPLC-MS. It was established that the multistep gradient elution developed for RP-TLC separation of pigments can be successfully used as a pilot method for the rational design of gradient elution in RP-HPLC for the separation of the same pigments. FT-IR and MS measurements were unable to identify the exact chemical structures of the main pigment fractions, the presence of OH, =CH and C=O (RP-TLC-FT-IR) and OH and NH, substructures (RP-HPLC-MS) was confirmed. It was assumed that the main pigment fractions are oxidation polymers originating from monomer molecules containing polar substructures and double bonds in the alkyl chain which are liable for oxidation during the aerobic fermentation process.     

Phase separation and disorder in half metallic ferromagnetic manganite thin films: A theoretical study looking forward low noise nano-devices

The resistivity of thin La_0.7Sr_0.3MnO₃ films was first investigated in a wide temperature (T) range (10–750 K). Films grown by different techniques and on several substrates enabled to analyze samples with different amounts of disorder. The aim of this work was to elucidate the nature of the metal–insulator (M–I) transition occurring at T = T_p in these films and its relation with the different kinds of inhomogeneities they could present like intrinsic electric disorder and co-existence of two different electrical and/or magnetic phases. The low-temperature resistivity state was described mostly by a law which scales as T with  ≈ 2.5. This supports the theoretical proposal of single magnon scattering in presence of minority spin states localized by the disorder. In the whole range of temperatures the experimental data are found to be consistent with a phase separation (PS) scenario. In order to go through the origin of the characteristic length scale of inhomogeneity found, preliminarily low frequency noise measurements as a function of T in a range of temperature around the M–I transition were made. The samples used were patterned using photolithography into bridges with various widths and lengths. No clear sign of separation phase dynamic has been observed in our noise measurements. Unexpectedly the normalized Hooge parameter _H/n was found not to be volume (Ω) independent. The LSMO electrical properties may strongly be driven by disorder and new design for magnetoresistance sensors may have to take into account their intrinsic PS.     

PCDD, PCDF, and PCB contamination of air and inhalable particulate in Rome

Summary The isomer specific determination of PCDD, PCDF and PCB was carried out on samples of air and inhalable particulate from Rome. Samples were taken daily for six months and pooled to yield two samples per month. Normal PCDD+PCDF concentrations expressed in TEQ ranged from 48 to 87 fg/m³, while total PCB ranged from 0.1 to 1.4 ng/m³. The 2, 3, 7, 8-substituted PCDD and PCDF congener pattern is shown together with the PCB congener pattern.     

Testing equality in lisp-like environments

A function is presented to test equality between lists. In any case the function requires at most one single traversal of the lists and behaves as follows:

1. if there are no cycles, it works as standardEQU AL functions;
2. if there are cycles, it does not give information about equality, but it can detect cycles, i.e. it signals which lists are cyclic.

A simplified version of the function is also considered which is always at least as efficient as standardEQU AL; it grants protection against cycles without signaling them. A coroutine organized version of the function is shown.     

An iterative extended Hückel calculation for some amino acids containing sulphur and selenium

Semiempirical iterative extended Hückel calculations are performed for the dipolar ions of cystine, cysteine, methionine and their selenium analogues. An attempt has been made to interprete the wave function of cysteine in terms of localized molecular orbitals.

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Zusammenfassung Semiempirische iterative Rechnungen wurden nach der erweiterten Hückeltheorie für die dipolaren Ionen Cystin, Cystein, Methionin und ihre Selen-Homologen durchgeführt. Für den Fall des Cysteins wurde die Wellenfunktion auf lokalisierte Orbitale transformiert.

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Résumé On a analisé les ions dipolaires de la cystine, cystéine, methionine et leurs analogues séléniates avec la méthode semiempirique de Hückel étendue itérative. On a cherché à intérpreter la fonction d'onde pour la cystéine dans le schème des orbitales moleculaires localisées.

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Work performed with the financial support of the Consiglio Nazionale delle Ricerche.     

Preparation and characterization of Mg(II)-, Ca(II) and Cd(II) complexes of 1,2-ethanediol and water

Mixed ligand complexes of different compositions were prepared with water, sulfate ion and 1,2-ethanediol as ligand. IR spectra and the thermoanalytical curves of the complexes were recorded. Oxygen atoms bound by one or two coordinate bonds to the metal ion, or by hydrogen-bonds in the crystal, were observed. As for the water molecule, 1,2-ethanediol molecules of crystal and monohydrate type were found, depending on the type of binding of the oxygen atoms.This revised version was published online in November 2005 with corrections to the Cover Date.     

CH...O and CH...F links form the cage structure of dioxane-trifluoromethane

The molecular beam Fourier transform microwave spectrum of 1,4-dioxane-trifluoromethane has been assigned and measured. The two subunits form a cage stabilized by one C-H...O and two C-H...F weak hydrogen bonds. The C-H...O link involves the axial lone pair of one of the two equivalent ring oxygens, while the two C-H...F bridges connect trifluoromethane to the two axial hydrogens in positions 3 and 5. The dissociation energy has been estimated from the D(J) centrifugal distortion parameter to be approximately 6.8 kJ/mol.     

Synthesis and Chemical and Electrochemical Characterization of Fe-S Carbonyl Clusters. X-ray Crystal Structures of [N(PPh(3))(2)](2)[Fe(5)S(2)(CO)(14)] and [N(PPh(3))(2)](2)[Fe(6)S(6)(CO)(12)

A reinvestigation of the redox behavior of the [Fe(3)(&mgr;(3)-S)(CO)(9)](2)(-) dianion led to the isolation and characterization of the new [Fe(5)S(2)(CO)(14)](2)(-), as well as the known [Fe(6)S(6)(CO)(12)](2)(-) dianion. As a corollary, new syntheses of the [Fe(3)S(CO)(9)](2)(-) dianion are also reported. The [Fe(5)S(2)(CO)(14)](2)(-) dianion has been obtained by oxidative condensation of [Fe(3)S(CO)(9)](2)(-) induced by tropylium and Ag(I) salts or SCl(2), or more straightforwardly through the reaction of [Fe(4)(CO)(13)](2)(-) with SCl(2). The [Fe(6)S(6)(CO)(12)](2)(-) dianion has been isolated as a byproduct of the synthesis of [Fe(3)S(CO)(9)](2)(-) and [Fe(5)S(2)(CO)(14)](2)(-) or by reaction of [Fe(4)(CO)(13)](2)(-) with elemental sulfur. The structures of [N(PPh(3))(2)](2)[Fe(5)S(2)(CO)(14)] and [N(PPh(3))(2)](2)[Fe(6)S(6)(CO)(12)] were determined by single-crystal X-ray diffraction analyses. Crystal data: for [N(PPh(3))(2)](2)[Fe(5)S(2)(CO)(14)], monoclinic, space group P2(1)/c (No. 14), a = 24.060(5), b = 14.355(6), c = 23.898(13) ?, beta = 90.42(3) degrees, Z = 4; for [N(PPh(3))(2)](2)[Fe(6)S(6)(CO)(12)], monoclinic, space group C2/c (No. 15), a = 34.424(4), b = 14.081(2), c = 19.674(2) ?, beta = 115.72(1) degrees, Z = 4. The new [Fe(5)S(2)(CO)(14)](2)(-) dianion shows a "bow tie" arrangement of the five metal atoms. The two Fe(3) triangles sharing the central Fe atom are not coplanar and show a dihedral angle of 55.08(3) degrees. Each Fe(3) moiety is capped by a triply bridging sulfide ligand. The 14 carbonyl groups are all terminal; two are bonded to the unique central atom and three to each peripheral iron atom. Protonation of the [Fe(5)S(2)(CO)(14)](2)(-) dianion gives reversibly rise to the corresponding [HFe(5)S(2)(CO)(14)](-) monohydride derivative, which shows an (1)H-NMR signal at delta -21.7 ppm. Its further protonation results in decomposition to mixtures of Fe(2)S(2)(CO)(6) and Fe(3)S(2)(CO)(9), rather than formation of the expected H(2)Fe(5)S(2)(CO)(14) dihydride. Exhaustive reduction of [Fe(5)S(2)(CO)(14)](2)(-) with sodium diphenyl ketyl progressively leads to fragmentation into [Fe(3)S(CO)(9)](2)(-) and [Fe(CO)(4)](2)(-), whereas electrochemical, as well as chemical oxidation with silver or tropylium tetrafluoroborate, in dichloromethane, generates the corresponding [Fe(5)S(2)(CO)(14)](-) radical anion which exhibits an ESR signal at g = 2.067 at 200 K. The electrochemical studies also indicated the existence of a subsequent one-electron anodic oxidation which possesses features of chemical reversibility in dichloromethane but not in acetonitrile solution. A reexamination of the electrochemical behavior of the [Fe(3)S(CO)(9)](2)(-) dianion coupled with ESR monitoring enabled the spectroscopic characterization of the [Fe(3)S(CO)(9)](-) radical monoanion and demonstrated its direct involvement in the generation of the [Fe(5)S(2)(CO)(14)](n)()(-) (n = 0, 1, 2) system.