Model Compounds for Iron Proteins. Structures and Magnetic, Spectroscopic, and Redox Properties of Fe(III)M(II) and [Co(III)Fe(III)](2)O Complexes with (&mgr;-Carboxylato)bis(&mgr;-phenoxo)dimetalate and (&mgr;-Oxo)diiron(III) Cores

A series of heterobimetallic complexes of the type [Fe(III)M(II)L(&mgr;-OAc)(OAc)(H(2)O)](ClO(4)).nH(2)O (2-5) and [{Fe(III)Co(III)L(&mgr;-OAc)(OAc)}(2)(&mgr;-O)](ClO(4))(2).3H(2)O (6) where H(2)L is a tetraaminodiphenol macrocyclic ligand and M(II) = Zn(2), Ni(3), Co(4), and Mn(5) have been synthesized and characterized. The (1)H NMR spectrum of 6 exhibits all the resonances between 1 and 12 ppm. The IR and UV-vis spectra of 2-5 indicate that in all the cases the metal ions have similar coordination environments. A disordered crystal structure determined for 3 reveals the presence of a (&mgr;-acetate)bis(&mgr;-phenoxide)-Ni(II)Fe(III) core, in which the two metal ions have 6-fold coordination geometry and each have two amino nitrogens and two phenolate oxygens as the in-plane donors; aside from the axial bridging acetate, the sixth coordination site of nickel(II) is occupied by the unidentate acetate and that of iron(III) by a water molecule. The crystal structure determination of 6 shows that the two heterobinuclear Co(III)Fe(III) units are bound by an Fe-O-Fe linkage. 6 crystallizes in the orthorhombic space group Ibca with a = 17.577(4) ?, b = 27.282(7) ?, c = 28.647(6) ?, and Z = 8. The two iron(III) centers in 6 are strongly antiferromagnetically coupled, J = -100 cm(-1) (H = -2JS(1).S(2)), whereas the other two S(1) = S(2) = (5)/(2) systems, viz. [Fe(2)(III)(HL)(2)(&mgr;-OH)(2)](ClO(4))(2) (1) and the Fe(III)Mn(II) complex (5), exhibit weak antiferromagnetic exchange coupling with J = -4.5 cm(-1) (1) and -1.8 cm(-1) (5). The Fe(III)Ni(II) (3) and Fe(III)Co(II) (4) systems, however, exhibit weak ferromagnetic behavior with J = 1.7 cm(-1) (3) and 4.2 cm(-1) (4). The iron(III) center in 2-5 exhibits quasi-reversible redox behavior between -0.44 and -0.48 V vs Ag/AgCl associated with reduction to iron(II). The oxidation of cobalt(II) in 4 occurs quasi-reversibly at 0.74 V, while both nickel(II) and manganese(II) in 3 and 5 undergo irreversible oxidation at 0.85 V. The electrochemical reduction of 6 leads to the generation of 4.     

Some new fluorine exchange reactions of perfluoroalkyliodine(V)fluorides

The perfluoroalkyliodine (V) fluorides CF₃IF₄ and CF₃IOF₂ react with many alcohols, acids and anhydrids in solution to give fluorine exchange. In all these reactions we observed equilibria, e.g.:

These reactions depend strongly on the kind of the reacting compounds and on the conditions, and they can be followed by n.m.r. spectroscopy. When trying to isolate the new derivatives always decomposition takes place.These reactions, the n.m.r. spectra, the properties of the new compounds and the decomposition reactions will be reported.     

A theory of molecules in molecules

SCF wave functions have been calculated using a minimal atomic basis set of Gaussian lobe functions for the para-, meta-, and ortho-forms of the molecules C₆H₄XY, where X, Y can be either of CN, OH, or F. It is found that in all cases the total energies increase in the sequence meta-, para-, ortho-compound. For the molecules containing the CN group the energy differences are extremely small (0.1–1 kcal/mole) for the other molecules they are one to two orders of magnitude larger. The reliability of these results is discussed. The theory of molecules in molecules is applied to these cases. The wave function of C₆H₄XY is constructed from the fragments C₆H₅X and HY by transferring some of the localized orbitals of the wave functions of the fragments and recalculating the orbitals in the region of interaction. For the molecules containing the CN group the energy differences are too small so that they are not correctly reproduced except by the most exact calculations, which involve no approximations other than the transfer of localized orbitals. For the other molecules satisfactory results are obtained.     

Modellrechnungen an einigen Siliziumwasserstoffverbindungen vom Typ SiHn,SiH n + und SiH n − nach der Einzentrenmethode

Zusammenfassung Es werden molekulare Struktur, Energie des Grundzustandes, Bindungsabstände, Bindungsenergie, Ionisierungsenergie und Protonenaffinität der Siliziumwasserstoffverbindungen SiH _n , SiH _n ⁺ und SiH_n ^– (n=3, 4 oder 5) nach der Einzentrenmethode berechnet.

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OCE-calculations on some silicon hydrides of the type SiH _n , SiH _n ⁺ and SiH _n ^–

OCE-Calculations are reported for molecular structures, ground state energies, bond distances, binding energies, ionization potentials and proton affinities of the silicon hydrides SiH _n , SiH _n ⁺ and SiH _n ^– (n=3, 4 or 5).

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Résumé Calcul par la méthode monocentrique de la structure moléculaire, de l'énergie de l'état fondamental, des longueurs de liaison, des énergies de liaison, des potentiels d'ionisation et des affinités protoniques pour les hydrures de silicium SiH _n , SiH _n ⁺ et SiH _n ^– (n=3, 4 ou 5).

     

Erweiterte Spiegelungsgruppen metrischer Vektorräume

The extended reflection groups of a metric vector space (V,f) are introduced and defined by a system of generators and a set of defining relations. It can be proved that they are isomorphic to certain subgroups of the orthogonal groups. The main result of the underlying paper is that these groups can be characterized by a few properties among which we mention the validity of the transitivity theorem and the property of — intersecting . Finally, we obtain a characterization of the (full) groups O^*(V,f) in the case dim V1.

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Herrn Professor Dr. Reinhold Baer zum 75. Geburtstag gewidmet     

Eine Erweiterung des Riemann-Lebesgue-Lemmas

It is proved that iff∈L ₁(?),f'∈L ₁(?) and ∫∣x∣ ⁱ ∣f(x)∣dx<∞ fori=1, ...,k?1 and ifA=(a _ij ) is a (k×k)-matrix with non-vanishing determinant, for $$\tilde f_A (\zeta ): = \smallint \exp (i\zeta _1 \sum\limits_{j = 1}^k {a_{1j} x^j } + ... + i\zeta _k \sum\limits_{j = 1}^k {a_{kj} x^j } )f(x)dx$$ the following relation holds: $$\tilde f_A (\zeta ) = O(\left\| \zeta \right\|)^{ - b_k } with b_k : = (\sum\limits_{j = 1}^k {j!)^{ - 1} } for k \in \mathbb{N}$$ .     

Das gemischte Volumen als Distribution

It is shown that there exists a distribution T on ⁿ ( unit sphere of Euclidean n-space) such that the mixed volume V(K₁,...,K_n) equals for all convex bodies K_i, where is the support function of k_i and denotes the tensor product. As a consequence, mixed volumes are approximated uniformly by n-fold integrals of the corresponding support functions.     

Multiple bonds between main group elements and transition metals, 155. (Hexamethylphosphoramide) methyl(oxo) bis(η-peroxo)rhenium(VII), the first example of an anhydrous rhenium peroxo complex: crystal structure and catalytic properties

Methyl(oxo)bis(η²-peroxo)rhenium(VII)1, the active species of the system CH₃ReO₃/H₂O₂ in the catalytic oxidation of different organic and organometallic compounds, is stabilized by a water molecule attached to the rhenium center. This water molecule can be removed and substituted by hexamethylphosphoramide (HMPA) to yield (hexamethylphosphoramide)methyl(oxo)bis(η²-peroxo rhenium(VII) (3). The synthesis, crystal structure (X-ray difraction study), and catalytic properties of which compound are reported. Crystal data are as follows: monoclinic, space group P2₁/n, A = 900.76(7) pm, B = 1229.80(11) pm, C = 1318.57(11) pm, β = 90.251(7)°, R_w = 0.034 for 1878 reflections. The catalytic properties of compound 3 in the oxidation of olefins with H₂O₂ are similar to those of 1.     

Nucleosides. Part LX. Synthesis and Characterization of Monomeric Cordycepin-Vitamin and Cordycepin-Lipid Conjugates Model Substances for Biodegradable Ester and Carbonate Linkages in Conjugates and Potential Inhibitors of HIV-1 Replication

Monomeric 3′-deoxyadenosine (cordycepin) was modified at the 2′-O- ( 13–18 ) and 5′-O-position ( 25–29 ) by the vitamins E, D₂, and A and by the two lipids 1,2-di-O-palmitoylglycerol and 1,2-di-O-hexadecylglycerol via succinate or carbonate linkages. The base-labile conjugates afforded protection groups like the 2-(4-nitro-phenyl)ethoxycarbonyl (npeoc) and monomethoxytrityl group (MeOTr) that are cleavable without harming the ester and carbonate bonds, respectively. Monomeric conjugates of cordycepin and vitamin E, vitamin D₂, 1,2-di-O-palmitoylglycerol, and 1,2-di-O-hexadecylglycerol (see 13, 14, 17, 18, 25, 26, 28 , and 29 ) inhibited HIV-1-induced syncytia formation 1.7 to 6.2 fold compared to 1.5-fold for cordycepin (see Table); IC₅₀ values for 25 and 28 were 257 and 267 m?M , respectively. In addition, the monomeric cordycepin-vitamin and -lipid conjugates inhibited HIV-1 RT activity 28–49% which compares with a 13% inhibition of HIV-1 RT observed for cordycepin. The minimal inhibition of HIV-1-induced syncytia formation and HIV-1 RT activity did not proceed by the activation of RNase L. The monomeric conjugates tested ( 13, 14 ) increased PKR expression.     

Recycling and screen-segmented column isotachophoresis, two free-fluid approaches for fractionation of proteins.

Recycling and screen-segmented column isotachophoresis (ITP), two approaches for the milligrams to grams preparative-scale purification of proteins, are discussed and compared. Recycling ITP was performed in a recycling free-flow focusing apparatus. In this process, fluid flows rapidly through a narrow channel and the effluent from each channel is reinjected into the electrophoresis chamber through the corresponding input port. The residence time in the cell is of the order of 1 s per single pass, which does not allow complete separation, so recycling is essential to attain the steady state. Immobilization of the advancing zone structure is obtained via a controlled counterflow. Thirty fractions of about 4 ml each are obtained. Column ITP was executed in a Rotofor apparatus and in a similar column operated vertically and without rotation. These instruments feature a screen-segmented annular separation space with twenty subcompartments of about 2 ml each. With both approaches, the collected fractions were analysed separately for conductivity, pH and UV absorbance. Selected fractions were characterized by analytical electrophoretic methods. Examples presented include the cationic and anionic ITP behaviour of model proteins, including bovine serum albumin, ovalbumin and ribonuclease A, and the ITP removal of the major impurities from a commercial ovalbumin sample. These examples revealed that the screen-segmented column is suitable for ITP protein purification and operates optimally in a horizontal rotating mode and without internal cooling. The recycling experiments showed that counterflow improves separation and the steady-state patterns are dependent on the fluid layer thickness in the separation cell but, with a given gap, essentially independent of applied current and recycling pump rate.