Ferromagnetism in a dinuclear nickel(II) complex containing triethylenetetramine and tricyanomethanide

Triethylenetetramine (L(4)) was used as a tetradentate blocking ligand that, after complexation with Ni(II), leaves two sites ready for ligation with tricyanomethanide. The formed binuclear complex [L(4)Ni(NCC(CN)CN)(2)NiL(4)](ClO(4))(2) exhibits a ferromagnetic coupling with J/hc = +0.15 cm(-1) and g(Ni) = 2.126; below 16 K, a ferromagnetic ordering is evidenced by ac magnetic susceptibility (both in-phase and out-of-phase), magnetization, field-cooled magnetization, and zero-field-cooled magnetization measurements.     

Multinuclear NMR Studies of Ligand-Exchange Reactions on Analogous Technetium(V) and Rhenium(V) Complexes. Relevance to nuclear medicine

The kinetics of pyridine exchange on trans-[MO₂(py)₄]⁺ have been followed by ¹H-NMR in CD₃NO₂ for M = Re, Tc: k²⁹⁸S^?1 = (5.5 ± 0.1) × 10^?6, 0.04 ± 0.02; ΔH^≠/kJmol^?1 = 111 ± 3, 101 ± 9; ΔS^≠/JK^?1mol^?1 = +28 ± 10, +68 ± 35. For the Re^v complex, pyridine and oxygen exchanges have been measured simultaneously by ¹H- and ¹⁷O-NMR in deuterated water: k²⁹⁸/s^?1 = (8.6 ± 0.2) × 10^?6 (py), (14.5 ± 0.3) × 10^?6 (oxygen); ΔH^≠/kJmol^?1 = 111 ± 1, 91 ± 1; ΔS /JK^?1mol^?1 = +32 ± 3, ?32 ± 4. For both complexes, the rate law for pyridine exchange is first-order in complex and zero-order in pyridine; together with the activation parameter values, and the fact that the rate does not depend significantly on the nature of the solvent, this strongly implies the operation of a dissociative mechanism. The ratio of pyridine exchange rates for the Tc and Re complexes at room temperature is ca. 8000. The consequences of these observations for radiopharmaceutical synthesis are discussed.     

Quantitative Depth Profiling of K-Doped Fullerene Films Using XPS and SIMS

 Phenomena accompanying electrochemical doping of solid fullerene films with potassium were studied by sputter ion depth profiling (XPS and SIMS). The potassium distribution was determined, and artifacts associated with possible damage of the layer composition caused by ion impact were investigated and discussed. To compare the charge transfer while reductive doping is taking place at fullerene/solution interface with doping from gas phase, model layers were prepared and doped by potassium under UHV conditions. It was found that sputtering by Ar⁺ primary ions yields both accurate information on the alkaline metal distribution and on its concentration. Sputtering by O⁺ ions led to an enrichment of potassium, apparently due to the reactivity of oxygen with the fullerene matrix. It is shown that the reductive doping starts at the fullerene/solution interface. The concentration of potassium in the doped films was found to be lower than expected from the charge transferred during the electrochemical reduction. Other phase transformations such as hydrogenation are discussed. Received March 4, 2002; accepted July 26, 2002     

Correlation between molecular orbitals and doping dependence of the electrical conductivity in electron-doped metal-phthalocyanine compounds

We have performed a comparative study of the electronic properties of six different electron-doped metal-phthalocyanine (MPc) compounds (ZnPc, CuPc, NiPc, CoPc, FePc, and MnPc), in which the electron density is controlled by means of potassium intercalation. Despite the complexity of these systems, we find that the nature of the underlying molecular orbitals produces observable effects in the doping dependence of the electrical conductivity of the materials. For all the MPc's in which the added electrons are expected to occupy orbitals centered on the ligands (ZnPc, CuPc, and NiPc), the doping dependence of the conductivity has an essentially identical shape. This shape is different from that observed in MPc materials in which electrons are also added to orbitals centered on the metal atom (CoPc, FePc, and MnPc). The observed relation between the macroscopic electronic properties of the MPc compounds and the properties of the molecular orbitals of the constituent molecules clearly indicates the richness of the alkali-doped metal-phthalocyanines as a model class of compounds for the investigation of the electronic properties of molecular systems.     

Synthesis and Reactivity of Fluoro(Organyl)Phosphanes

Abstract

A new method for producing fluoro(organyl) phosphanes is presented. They are prepared by Cl/F-exchange from the corresponding chloro compounds using Et₃N.nHF as a fluorinating agent. Phosphanyl fluorophospharanes, R₂P-PR₂F₂, are found to be intermediates of the disproportionation of Fluoro (diorganyl) phosphanes. R₂PF react with aldehydes to form phosphinito phosphoranes, R₂PF₂-CHR'-OPR₂. Oxaphospholenes are formed in their reaction with α, β- unsaturated aldehydes. Furthermore, the reactions with 1.2-diketones, carboxylic acid derivatives, and covalent azides are described.