A Highly Active N‐Heterocyclic Carbene Manganese(I) Complex for Selective Electrocatalytic CO2 Reduction to CO

We report here the first purely organometallic fac‐[Mn^I(CO)₃(bis‐^MeNHC)Br] complex with unprecedented activity for the selective electrocatalytic reduction of CO₂ to CO, exceeding 100 turnovers with excellent faradaic yields (η_CO≈95 %) in anhydrous CH₃CN. Under the same conditions, a maximum turnover frequency (TOF_max) of 2100 s^?1 was measured by cyclic voltammetry, which clearly exceeds the values reported for other manganese‐based catalysts. Moreover, the addition of water leads to the highest TOF_max value (ca. 320 000 s^?1) ever reported for a manganese‐based catalyst. A Mn^I tetracarbonyl intermediate was detected under catalytic conditions for the first time.     

Molecular structure ofrac-(4R*,4aS*,10aS*)-4-nitro-1,2,3,4,4a,9,10,10a-octahydrophenanthren-4a-ol,an unusual by-product of nitration of a crude 9,10-dihydrophenanthrene

A new nitro-octahydrophenanthrenol has been isolated by nitration of a crude 9,10-dihydrophenanthrene, which was identified by nmr and X-ray diffraction analysis. Crystallographic and molecular structure confirmed the compound as therac-(4R^*,4aS^*,10aS^*)-4-Nitro-1,2,3,4,4a,9,10,10a-octahydrophenanthren-4a-ol. The crystal was triclinic, ,a=10.549(3),b=8.530(3),c=7.131(1)Å, =107.07(3), =91.62(3), =96.27(4)°. Cyclohexane and cyclohexene rings aretrans-fused and have chair and half-chair conformations, respectively. The molecules are associated by hydrogen bridge between the hydroxyl oxygen and both nitro oxygens.     

Quark-antiquark pair production via γW fusion at high energye + e − colliders

We calculate numerically the cross section for the process \(e^ + e^ - \to ve^ + Q_d \bar Q_u \) using the Weizsäcker-Williams approximation for the virtual photon. This process is a possible background for the detection of an “intermediate” Higgs via its decay into \(Q\bar Q\) pairs. The comparison with the signal allows us to conclude that actually it is not a problem for the Higgs search at high energye ⁺ e ^? colliders.     

Structural investigation on hexasubstituted benzene derivatives. Part 2: The structure of metadinitrotetramethylbenzene and molecular mechanics analysis on meta and ortho derivatives

C₁₀H₁₂N₂O₄ (M r=224.2) crystallizes in the monoclinic system, space groupP2₁/mwitha=15.462(4),b=7.926(3),c=8.972(3) Å;=90.2(1)°;V=1099.5(6) ų;Z=4;D _c=1.35 gcm^–3;(Cu-K)=8.6 cm^–1; =1.5418 Å;F(000)=472. The position of the molecule on a crystallographic mirror plane forces the NO₂ plane to be normal to the benzene ring. The-electron-withdrawing character of the NO₂ groups induces a deformation on the geometry of the benzene.     

Enlarging the size of calix[4]arene-crowns-6 to improve Cs/K selectivity: a theoretical and experimental study

Ab initio calculations in the gas-phase indicate that the substitution of an ethylene with a propylene moiety in the polyether bridge of 1,3-di-iso-propoxycalix[4]arene-crowns-6 could result in an enhanced Cs⁺/K⁺ selectivity which is of particular interest in nuclear waste treatment. We therefore synthesised two novel calix[4]arene-crown-6 compounds (1 and 2) having a propylene moiety in their structure and for this named calix[4]arene-propylene-crown-6. The structures of compounds 1 and 2 were elucidated by NMR in solution and for 1 also by X-ray diffraction studies in the solid state. Association constants (K_a) in CHCl₃ of the two novel calix-crowns were measured and pointed out a plateau selectivity towards alkali metal ions which was not predicted by molecular modelling calculations. These results indicate the important role played by the solvent molecules and counter-anions in binding for this class of ionophores.     

A convenient laboratory synthesis of 2-oxazoline

The reaction of 2-chloroethylformamide ( 1a ) with sodium hydride, in N-methyl-2-pyrrolidone, at reduced pressure, gave anhydrous 2-oxazoline ( 2a ) in good yield.     

Asymmetric synthesis by chiral ruthenium complexes : IV. Reduction of carbon-carbon double bonds in prochiral α,β-unsaturated carboxylic acids by hydrogen transfer catalysed by H4Ru4(CO)8[(−)-DIOP]2

The enantioface-discriminating hydrogen transfer reduction of αβ-unsaturaged acids takes place at 120°C in the presence of H₄Ru₄(CO)₈[()-DIOP]₂. Secondary alcohols are satisfactory hydrogen donors. Selectivity, optical yields, and rates are lower than those obtained when working in the presence of hydrogen under pressure.     

Laser fluorescent microirradiation: Two examples of application to biology. a. Study of the functional state of chromatin; b. Study of hematoporphyrin derivative (HpD) in cells

In this paper two examples are presented of the application of laser fluorescent microirradiationto biology. The experiments, performed using a pulsed-laser microfluorometer with high spatial and temporal resolution, concern: (i) a study of the functional state of chromatin and (ii) a study of the fluorescence properties of Hematoporphyrin-derivative in tissue- and culture-cells. (i) The in situ evaluation of the functional state of chromatin has been done in chromosomes and nuclei “in toto” stained with the fluorescent probe Quinacrine Mustard. It has been found that chromatin fractions with different degree of activity, morphologically recognizable at the microscope, present fluorescence decay times markedly different, with a longer decay time for active chromatin. This result has been attributed to the stainability of DNA, which appears to be lower for active chromatin than for the inactive one. A similar result has been obtained in a preliminary experiment on cultures of human lymphocytes, after activation with Phytohemagglutinin. (ii) The fluorescent properties of Hematoporphyrin-derSvative have been studied in single cells, obtained from both normal and tumor tissues and cultures. In agreement with the results obtained with other techniques in tissues, it has been found that the tumor cells examined present an HpD uptake higher than that of the normal cells of the corresponding tissue, and that, within a cell, HpD becomes localized mainly in the cytoplasm. Preliminary results indicate a difference in the fluorescence decay time between stimulated and unstimulated human lymphocytes treated with HpD. Furthermore, it has been found that the fluorescence decay time is different in cells as compared with HpD solution and that the presence of HpD stabilizes cell autofluorescence.     

Solvent extraction studies of addition compounds of metal halides and triphenylphosphine, -arsine and -stibine : Detection of palladium

Palladium, is very efficiently extracted as PdI₂·₂(C₆H₅)₃Sb from weakly acidic medium, containing excess of iodide with a solution, of triphenylstibinc in cyclohexane. A test for the detection of palladium is described based on this property. In the presence of sulfite and in the absence of cyanide, which inhibits the reaction, the test is specific. A pink to red color develops in the organic layer enabling the identification of as little as 0.07 μg- Pd.