Inorganic-organic hybrids of the p,p′-diphenylmethylenediphosphinate ligand with bivalent metals: a new 2D-layered phenylphosphinate zinc(II) complex

By reaction of Zn(CH₃COO)₂ with p,p′-diphenylmethylenediphosphinic acid in water a new inorganic-organic polymeric hybrid of formula [Zn(CH₂(P(Ph)O₂)₂)] has been synthesized and completely characterized. The X-ray analysis established that the structure consists of 2D-layered polymeric array, the 2D-sheets being built up through strong covalent linkages between the zinc metal and the oxygen donors of the phenylphosphinate ligand. The 2D-layers, which are featuring a mesh-net fashion, present voids of various dimensionality, up to 24-membered rings. The organic parts of the hybrid ligand, namely the phenyl rings, are shielding the inorganic skeleton of the layers, preventing the propagation of the polymer in the third dimension. No water molecules are present in the lattice, both of coordination and crystallization. Crystal data are: monoclinic, P2₁/c, a=11.840(2), b=9.646(9), c=12.516(5) Å, β=95.03(2), V=1423.9(15) Å³, Z=4. The solid material has been characterized by ³¹P MAS NMR spectroscopy and thermogravimetric analysis.     

Sui connettivi tra eventi e l’impostazione assiomatica del calcolo delle probabilità

Riassunto Ammesso il connettivoaut sull’insieme degli eventi, si mostra come risultano definiti i connettivivel edet. Si deducono quindi i teoremi delle probabilità totali e delle probabilità composte.

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Résumé Admis le connectifaut sur l’ensemble des événements, on montre comme résultent définis les connectifvel etet. On déduit de là les théorèmes des probabilités totales et des probabilités composées.

     

Reduction of the contribution of electrode polarization effects in the radiowave dielectric measurements of highly conductive biological cell suspensions

Electrode polarization effects in dielectric spectra of highly conductive biological cell suspensions cause a severe difficulty in the estimation of dielectric parameters of cells under physiological conditions. This problem becomes particularly serious with the increase of the electrical conductivity of the sample, preventing the use of low frequencies in the characterization of biological systems, especially aqueous biological systems.Although a variety of methods to correct the electrode polarization have been proposed in the past, no simple technique for its correction has been available so far. Since the magnitude of the polarization effect can be time-dependent owing to changes in the conductance of the suspending medium or to possible alteration in the electrode surface structure, it is clear that correction procedure should be based on a kind of "self-correction" method, avoiding the so-called "comparison methods" which, on the contrary, require time-independent effects.This note is aimed to address this problem considering an electrode polarization modelled by a constant phase angle (CPA) element in series with the sample admittance. A scaling-law frequency dependence has found to describe the a.c. response of the interface between the electrode and the bulk electrolyte solution. Although this approach has been extensively proposed in the past in the analysis of dielectric spectra of biological suspensions, we have somewhat modified the way it has been previously applied and have re-examined in detail its effectiveness in typical systems of biological interest. The results give support to the proposed analysis, allowing the complete low-frequency dielectric spectra characterization at frequencies of the order of 1 kHz for samples with a bulk ionic conductivity as large as that of the order of 1 mho/m. Typical examples with different dielectric behaviours are extensively discussed in order to show the applicability of the proposed method to biological samples.     

Thermal decomposition of bis-(DL-valinato)copper(II) and bis-(DL-methioninato)copper(II)

A kinetic study of the thermal decomposition of the complexes bis-(DL-valinato)copper(II) and bis-(DL-methioninato)copper(II) was carried out using thermogravimetry in a dynamic regime, following the theoretical model of Satava and including the equation used by Johnson and Gallagher:1/1––1=kt. Kinetic parameters were calculated and are compared with those obtained previously for the complex bis-(L-tryptophanato)copper(II). The sequence of thermal stability found is: Cu(DL-Val)₂22.

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Zusammenfassung Die thermische Zersetzung der Komplexe Bis-(DL-valinato)kupfer(II) und Bis-(DL-methioninato)kupfer(II) wurde thermogravimetrisch im dynamischen Regime untersucht, indem von dem theoretischen Modell von atava Gebrauch gemacht und die von Johnson und Gallagher benutzte Gleichung 1/1-–1=kt einbezogen wurde. Kinetische Parameter wurden berechnet und mit den kürzlich für den Komplex Bis-(L-tryptophanato)kupfer(II) erhaltenen parametern verglichen. Die Stabilität der Komplexe nimmt in folgender Reihenfolge zu: Cu(DL-Val)₂22.

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-(-)- -(L-) (II) , -: 1/1– –1=kt. -(L-) (II). Cu(DL-Val)₂22.

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Presented at the 1985 World Conference on Thermal Analysis, Bad Hofgastein, Austria.     

Specific heat behaviour of K2SeO4 in the 48K–800K temperature range a new phase transition

A calorimetric study performed on the ferroelectric K₂SeO₄ in the 48K–800K temperature range confirmed the existence of three phase transition and revealed the occurrence of a new one at 56.03±0.05K (T^IV_c). The critical measurements for the commensurate-incommensurate phase transition seem to show a cross-over behaviour.     

Revealing the Chemical State of Palladium in Operating In2O3 Gas Sensors: Metallic Pd Enhances Sensing Response and Intermetallic InxPdy Compound Blocks It

The sensing response of metal oxides activated with noble metal nanoparticles is significantly influenced by changes to the chemical state of corresponding elements under operating conditions. Here, a PdO/rh-In₂O₃ consisting of PdO nanoparticles loaded onto rhombohedral In₂O₃ was studied as a gas sensor for H₂ gas (100–40000 ppm in an oxygen-free atmosphere) in the temperature range of 25–450 °C. The phase composition and chemical state of elements were examined by resistance measurements combined with synchrotron-based in situ X-ray diffraction and ex situ X-ray photoelectron spectroscopy. As found, PdO/rh-In₂O₃ undergoes a series of structural and chemical transformations during operation: from PdO to Pd/PdH_x and finally to the intermetallic In_xPd_y phase. The maximal sensing response (R_N2/R_H2) of ∼5 ⋅ 10⁷ towards 40000 ppm (4 vol %) H₂ at 70 °C is correlated with the formation of PdH_0.706/Pd. The In_xPd_y intermetallic compounds formed around 250 °C significantly decrease the sensing response.