The complexification and degree of a semi-algebraic set

The complexification of a semi-algebraic set is the smallest complex algebraic set containing S. Let S be defined by s polynomials of degrees less than d. We prove that the geometric degree of the complexification is less than . Received: 9 January 1997; in final form: 11 August 2000 / Published online: 17 May 2001     

Heterobimetallic Eu(iii)/Pt(ii) single-chain nanoparticles: a path to enlighten catalytic reactions

We introduce the formation and characterization of heterometallic single-chain nanoparticles entailing both catalytic and luminescent properties. A terpolymer containing two divergent ligand moieties, phosphines and phosphine oxides, is synthesized and intramolecularly folded into nanoparticles via a selective metal complexation of Pt(ii) and Eu(iii). The formation of heterometallic Eu(iii)/Pt(ii) nanoparticles is evidenced by size exclusion chromatography, multinuclear NMR (¹H, ³¹P{¹H}, ¹⁹F, ¹⁹⁵Pt) as well as diffusion-ordered NMR and IR spectroscopy. Critically, we demonstrate the activity of the SCNPs as a homogeneous and luminescent catalytic system in the amination reaction of allyl alcohol.

A bifunctional terpolymer containing two orthogonal ligand moieties was synthesized, giving way to the facile formation of heterometallic Eu(iii)/Pt(ii) single-chain nanoparticles, which display both catalytic and luminescent properties.     

Exploiting the regioselectivity of pyroglutamate alkylations for the synthesis of 6-azabicyclo[3.2.1]octanes and 4-azabicyclo[3.3.0]octanes

Depending on the N-protecting group of pyroglutamates, the reactivity can be directed to the formation of 6-azabicyclo[3.2.1]octanes or 4-azabicyclo[3.3.0]octanes, which are conformationally restricted glutamate analogues.     

Determination of slight contamination by D-amino acids in natural amino acids

Conclusions The problem of using gas chromatography for the estimation of slight contamination by D-amino acids in natural L-amino acids has been examined. The threshold amount of D-isomer detectable by the gas chromatographic method, using a drift conpensating integrator, amounts to 0.5%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2771–2772, December, 1967.     

Synthetic protocols and building blocks for molecular electronics

Simple and readily accessible aryl bromides are useful building blocks for thiol end-capped molecular wires. Thus, 4-bromophenyl tert-butyl sulfide and 1-bromo-4-(methoxymethyl)benzene serve as precursors for a variety of oligo(phenylenevinylene) and oligo(phenyleneethynylene) wires via efficient synthetic transformations as presented in this paper.     

Relative kinetics of the radical addition of benzyl bromide to unsaturated compounds

The relative rate constants of the addition of the C₆H₅CH₂ radical to unsaturated compounds CH₂=CHX (X = C₄H₉, SiMe₃, CF₃, CO₂Me, CN) were determined under the conditions of initiation by the Fe(CO)₅ + DMF system or by benzoyl peroxide. Depending on the values of the relative addition rate constants, the monomers can be arranged into the following series (X): CF₃C₄H₉32Me5 + DMF system, the addition stage proceeds by a free radical mechanism.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2017–2022, September, 1992.     

On the temporal analysis of special GERT networks using a modified Markov renewal process

In this paper we show how to represent a STEOR network (GERT network with only nodes of the stochastic exclusive-or Type) by a modified Markov renewal process. The computation of the renewal kernel of this process yields the temporal analysis of the network.

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Zusammenfassung Es wird gezeigt, wie ein STEOR-Netzplan (GERT-Netzplan, der nur Knoten vom Typ stochastisch exklusiv-oder enthält) durch einen modifizierten Markowschen Erneuerungsprozeß beschrieben werden kann. Die Bestimmung der Erneuerungsfunktionen dieses Prozesses liefert die Auswertung des STEOR-Netzplans (im Sinne der Zeitplanung).

     

Ternäre Halogenide der Seltenen Erden vom Typ A2MX5 (A = K,In, NH4, Rb,Cs; X = Cl,Br, I)

Ternary Rare-Earth Halides of the A₂MX₅ Type (A = K, In, NH₄, Rb, Cs; X = Cl, Br, I) Ternary rare-earth (=M) chlorides, bromides, and iodides In₂MCl₅, (NH₄)₂MCl₅, Rb₂MCl₅, Cs₂MCl₅, CsRbMCl₅, K₂MBr₅, Rb₂MBr₅, K₂MI₅, and Rb₂MI₅ have been synthesized. Single crystals of In₂PrCl₅, Rb₂PrCl₅, K₂PrBr₅, and K₂PrI₅ were grown and the structures refined. The other halides were characterized by x-ray powder patterns. They are isotypic either with K₂PrCl₅(orthorhombic, Pnma, Z = 4, hexagonal arrangement of chains of edge-connected polyhedra [PrX₇]) or with Cs₂DyCl₅ (orthorhombic, Pbnm, Z = 4, hexagonal arrangement of cis-corner-connected octahedra [DyCl₆]) which may be discriminated in structure field diagrams. The thermal expansion was investigated für Cs₂LuCl₅ and Rb₂PrX₅ (X = Cl, Br, I).     

Electronic structure and reactivity of high-spin iron--alkyl- and--pterinperoxo complexes

The spectroscopic properties and electronic structure of the four-coordinate high-spin [FeIII(L3)(OOtBu)]+ complex (1; L3 = hydrotris(3-tert-butyl-5-isopropyl-1-pyrazolyl)borate; tBu = tert-butyl) are investigated and compared to the six-coordinated high-spin [Fe(6-Me3TPA)(OHx)(OOtBu)]x+ system (TPA = tris(2-pyridylmethyl)amine, x = 1 or 2) studied earlier [Lehnert, N.; Ho, R. Y. N.; Que, L., Jr.; Solomon, E. I. J. Am. Chem. Soc. 2001, 123, 12802-12816]. Complex 1 is characterized by Raman features at 889 and 830 cm-1 which are assigned to the O-O stretch (mixed with the symmetric C-C stretch) and a band at 625 cm-1 that corresponds to nu(Fe-O). The UV-vis spectrum shows a charge-transfer (CT) transition at 510 nm from the alkylperoxo pi v* (v = vertical to C-O-O plane) to a d orbital of Fe(III). A second CT is identified from MCD at 370 nm that is assigned to a transition from pi h* (h = horizontal to C-O-O plane) to an Fe(III) d orbital. For the TPA complex the pi v* CT is at 560 nm while the pi h* CT is to higher energy than 250 nm. These spectroscopic differences between four- and six-coordinate Fe(III)-OOR complexes are interpreted on the basis of their different ligand fields. In addition, the electronic structure of Fe-OOPtn complexes with the biologically relevant pterinperoxo ligand are investigated. Substitution of the tert-butyl group in 1 by pterin leads to the corresponding Fe(III)-OOPtn species (2), which shows a stronger electron donation from the peroxide to Fe(III) than 1. This is related to the lower ionization potential of pterin. Reduction of 2 by one electron leads to the Fe(II)-OOPtn complex (3), which is relevant as a model for potential intermediates in pterin-dependent hydroxylases. However, in the four-coordinate ligand field of 3, the additional electron is located in a nonbonding d orbital of iron. Hence, the pterinperoxo ligand is not activated for heterolytic cleavage of the O-O bond in this system. This is also evident from the calculated reaction energies that are endothermic by at least 20 kcal/mol.