Synthesis, structural analysis, and magnetic properties of ethylmalonate-manganese(II) complexes

Five manganese(II) complexes of formulas [Mn(2)(Etmal)(2)(H(2)O)(2)(L)](n) (1-4) and {[Mn(Etmal)(2)(H(2)O)][Mn(H(2)O)(4)]}(n) (5) with H(2)Etmal = ethylmalonic acid (1-5) and L = 1,2-bis(4-pyridyl)ethane (bpa) (1), 4,4'-azobispyridine (azpy) (2), 4,4'-bipyridyl (4,4'-bpy) (3), and 1,2-bis(4-pyridyl)ethylene (bpe) (4) were synthesized and structurally characterized by single crystal X-ray diffraction. Their thermal behavior and variable-temperature magnetic properties were also investigated. The structure of the compounds 1-4 consists of corrugated layers of aquamanganese(II) units with intralayer carboxylate-ethylmalonate bridges in the anti-syn (equatorial-equatorial) coordination mode which are linked through bis-monodentate bpa (1), azpy (2), 4,4'-bpy (3), and bpe (4) ligands to build up a three-dimensional (3D) framework. The structure of compound 5 is made up by zigzag chains of manganese(II) ions with a regular alternation of [Mn(H(2)O)(4)](2+) and chiral (either Δ or λ enantiomeric forms) [Mn(Etmal)(2)(H(2)O)](2-) units within each chain. In contrast to the bidentate/bis-monodentate coordination mode of the Etmal ligand in 1-4, it adopts the bidentate/monodentate coordination mode in 5 with the bridging carboxylate-ethylmalonate also exhibiting the anti-syn conformation but connecting one equatorial and an axial position from adjacent metal centers. The manganese-manganese separation through the carboxylate-ethylmalonate bridge in 1-5 vary in the range 5.3167(4)-5.5336(7) ?. These values are much shorter than those across the extended bis-monodentate N-donors in 1-4 with longest/shortest values of 11.682(3) (3)/13.9745(9) ? (4). Compounds 1-5 exhibit an overall antiferromagnetic behavior, where the exchange pathway is provided by the carboxylate-ethylmalonate bridge. Monte Carlo simulations based on the classical spin approach (1-5) were used to successfully reproduce the magnetic data of 1-5.     

High Pressure Processing at Subzero Temperature: Effect on Spoilage Microbiota of Poultry

Mechanically recovered poultry meat (MRPM) was treated at 350 and 450 MPa for 5 and 15 min at m 20 °C and then stored at 2 °C. Counts of mesophilic, psychrotrophic and lactic acid bacteria were determined at 1, 4 and 15 days of storage. Initial counts were ca. 7 log CFU/g for the three populations. High pressure induced lethalities of ca. 1.5 log CFU/g for mesophiles and psychrotrophs and, in some cases, ca. 2.5 log CFU/g for lactic acid bacteria. At 4 days, counts in pressurized samples increased less for mesophiles and psychrotrophs ( h 0.5 CFU/g) than for lactic acid bacteria ( S 1 log CFU/g). At 15 days, counts of the three populations were ca. 9 log CFU/g in all samples. High pressure processing at subzero temperature does not extend shelf-life of MRPM.     

Identification of two types of F centres in BaClF by endor

By means of an ENDOR investigation we have shown beyond doubt, that the optical bands at 2.83 and 2.25 eV belong to electrons trapped at Cl^?-vacancies (F(Cl^?)-centres)), whereas the bands at 2.33 and 2.82 eV are due to electrons at F^? vacancies (F(F^?)-centres)). The current F-centre theory fails to explain the spin densities at nearest neighbour sites by one (F(Cl^?)) and two orders of magnitude (F(F^?)), respectively.Mit Hilfe einer ENDOR-Untersuchung haben wir eindeutig gezeigt, daβ die optischen Banden bei 2,83 und 2,25 eV zu Elektronen in Cl^?-Leerstellen (F(Cl^?)-Zentren)), die Banden bei 2,33 und 2,82 eV zu Elektronen in F^?-Leerstellen (F(F^?)-Zentren)) gehören. Theoretische Werte für die Spindichte der nächsten Nachbarn aufgrund der gegenwärtigen F-Zentren-theorie ergeben Diskrepanzen um eine (F(Cl^?)) bzw. zwei (F(F^?)) Gröβenordnungen.     

A short synthesis of praziquantel

The synthesis of praziquantel ( 1 ), a potent anthelmintic agent, is reported. The synthesis requires five steps and proceeds in 16% yield.     

Optical absorption and ESR study of F centres in BaClF and SrClF crystals

Magnetic and optical properties of two types of F centres, calledF(F^?) and F (Cl^?), created in BaClF and SrClF tetragonal crystals are described. The experimerttal position of the absorption bands and the [g] principal values of each centre are the following at 78K. In BaClF, $\text{F(}\text{Cl}{}^{\mathrm{?}}\text{): λ}{}_{\mathrm{}}\text{=438}\text{nm}\text{, λ}{}_{\mathrm{\perp }}\text{=550}\text{nm}\text{, g}{}_{\mathrm{\parallel }}\text{=1.9690 ± 0.0003, g}{}_{\mathrm{\perp }}\text{=1.9798±0.0003; F(}\text{F}{}^{\mathrm{?}}\text{): λ}{}_{\mathrm{\parallel }}\text{=532}\text{nm}\text{, λ}{}_{\mathrm{\perp }}\text{=}\text{430}\text{nm}\text{446}\text{nm}\text{, g}{}_{\mathrm{\parallel }}\text{=1.9836 ± 0.0003, g}{}_{\mathrm{\perp }}\text{=1.9695±0.0003.}\text{In SrCIF}\text{, F(}\text{Cl}{}^{\mathrm{?}}\text{): γ}{}_{\mathrm{\parallel }}\text{=380}\text{nm}\text{, λ}{}_{\mathrm{hu}}\text{=465}\text{nm}\text{, g}{}_{\mathrm{\parallel }}\text{=1.996±0.002, g}{}_{\mathrm{\perp }}\text{=1.993±0.002; F(}\text{F}{}^{\mathrm{?}}\text{): λ}{}_{\mathrm{\parallel }}\text{=410}\text{nm}\text{, λ}{}_{\mathrm{\perp }}\text{=}\text{345}\text{nm}\text{363}\text{nm}\text{, g}{}_{\mathrm{\parallel }}\text{=1.997±0.001, g}{}_{\mathrm{\perp }}\text{=1.993+0.001. (∥}\text{and}\text{⊥}$ refer to the light polarization or the magnetic field direction with respect to the fourfold axis of the crystal).This attribution disagrees with that proposed by Nicklaus and Fischer, but accounts for the values of the energy levels of F(F^?) and F(C1^?) in BaClF and SrClF calculated by S. Lefrant and A.H. Harker.     

Contact values for disparate-size hard-sphere mixtures

A universality ansatz for the contact values of a multicomponent mixture of additive hard spheres is used to propose new formulae for the case of disparate-size binary mixtures. A comparison with simulation data and with a recent proposal by Alawneh and Henderson for binary mixtures shows reasonably good agreement with the predictions for the contact values of the large–large radial distribution functions. A discussion on the usefulness and limitations of the new proposals is also presented.     

Asymmetric synthesis of (S)-(−)-tetrahydropalmatine and (S)-(−)-canadine via a sulfinyl-directed Pictet–Spengler cyclization

(S)-(?)-Tetrahydropalmatine 2 and (S)-(?)-canadine 4 were synthesized in three steps from (S)-6, in 33% and 34% overall yield, respectively. Thus, condensation of the (S)-(E)-sulfinylimines 10 and 11 with the carbanion derived from (S)-6 gave the tetrahydroisoquinolines 12 and 13, respectively, which upon TFA induced N-desulfinylation, and subsequent microwave assisted Pictet–Spengler cyclization effected both cyclization and C-desulfinylation producing (S)-(?)-tetrahydropalmatine 2 and (S)-(?)-canadine 4 in optically pure form.     

Methyl sulfinates as electrophiles in Friedel-Crafts reactions. Synthesis of aryl sulfoxides

The Friedel-Crafts reaction of methyl alkyl- and arylsulfinates with aromatic systems, activated by one or more electron-donating substituents (OH, OMe, NHR, NR(2)), provides alkyl aryl and diaryl sulfoxides under mild conditions and in moderate to good yields. The very high regioselectivity usually observed in these sulfinylation reactions is rationalized on the basis of a Wheland intermediate having a trigonal bypyramidal structure in which steric and electronic interactions are significant factors strongly destabilizing the attack to the ortho positions.