Intramolecular screening of crystal fields and the X-ray-photoemission determination of charge transfer in TTF-TCNQ

A recent controversy concerns the XPS data for TTF-TCNQ, which shows two binding energies for the N?1s level. We show that XPS chemical shifts due to charge flow on TCNQ, in response to the crystal potential, can cancel the Madelung splitting of the N?1s levels. Then we decompose the N?1s spectrum into its two components, which have widths characteristic of N?1s in TCNQ⁰ and TCNQ^?, and whose intensities suggest charge transfer of ～ 0.56–0.67.     

The Kondo effect in low temperature deposited Cu(Fe) films

Highly disordered Cu(Fe) films were prepared by condensing a dilute Cu(Fe) alloy onto a lHe temperature substrate. The Kondo temperature T′_K was computed by fitting the data to the Applebaum-Kondo resistivity formula. The computed T′_K was found to be the same as that of bulk, crystalline Cu(Fe).     

Superconducting tunneling in PdH

Tunneling measurements have been made on superconducting PdH films. The measured2Δ₀/kT_c ratio was 3.80 ± 0.15 meV. Structure was found in the tunneling density of states at an energy of 48 ± 2 meV, approximately the energy of optic phonons in PdH.     

Infrared active modes of cubic strontium titanate

It is shown that there are nine optically active modes of SrTiO₃ and not twelve as stated byNarayanan andVedam in a previous article in this Journal.     

3-pyrrolines are mechanism-based inactivators of the quinone-dependent amine oxidases but only substrates of the flavin-dependent amine oxidases

We previously reported that 3-pyrroline and 3-phenyl-3-pyrroline effect a time-dependent inactivation of the copper-containing quinone-dependent amine oxidase from bovine plasma (BPAO) (Lee et al. J. Am. Chem. Soc. 1996, 118, 7241-7242). Quinone cofactor model studies suggested a mechanism involving stoichiometric turnover to a stable pyrrolylated cofactor. Full details of the model studies are now reported along with data on the inhibition of BPAO by a family of 3-aryl-3-pyrrolines (aryl = substituted phenyl, 1-naphthyl, 2-naphthyl), with the 4-methoxy-3-nitrophenyl analogue being the most potent. At the same time, the parent 3-phenyl analogue is a pure substrate for the flavin-dependent mitochondrial monoamine oxidase B from bovine liver. Spectroscopic studies (including resonance Raman) on BPAO inactivated by the 4-methoxy-3-nitrophenyl analogue are consistent with covalent derivatization of the 2,4,5-trihydroxyphenylalanine quinone (TPQ) cofactor. The distinction of a class of compounds acting as an inactivator of one amine oxidase family and a pure substrate of another amine oxidase family represents a unique lead to the development of selective inhibitors of the mammalian copper-containing amine oxidases.     

Palladium-catalyzed asymmetric [3 + 2] trimethylenemethane cycloaddition reactions

Transition-metal-catalyzed trimethylenemethane (TMM) [3 + 2] cycloadditions provide direct routes to functionalized cyclopentanes. This reaction has been shown to be a highly chemo-, regio-, and diastereoselective process. We report a palladium-catalyzed asymmetric [3 + 2] trimethylenemethane (TMM) cycloaddition between 3-acetoxy-2-trimethylsilylmethyl-1-propene and various di- and trisubstituted olefins. Yields of exo-methylenecyclopentane products range from 59 to 99%, and enantiomeric excesses range from 58 to 92% ee.     

Effect of swelling on radiation-induced grafting of styrene to polyethylene

The radiation-induced grafting of low-density polyethylene in contact with styrene solution was studied. The effect of the degree of swelling of the polymer on the rate of grafting was investigated by diluting the styrene with methanol and with n-octane. For styrene-methanol solution, the rate of grafting was found to increase with degree of swelling, passing through a maximum when the sorbed solvent reaches 6.2 wt-% (70 vol-% methanol in the outside solution) and decreasing therafter. The methanol fraction of the sorbed liquid is far too small to cause precipitation of the grafted chains and inhibition of their termination rate. The dilution of styrene by octane has no effect on the swelling of polyethylene, but it decreases the grafting rate over the entire concentration range. The results are explained in terms of the concentration of sorbed monomer and the viscosity of the amorphous region of the polyethylene swollen by nonpolar liquids. Supporting evidence for the mechanism is presented in the form of grafting kinetic data as a function of dose rate (2.8 × 10²?9.5 × 10⁴ rad/hr), and post-irradiation grafting measurements for polyethylene in methanol-styrene (70/30, v/v). The data indicate that at the maximum grafting rate an optimum is achieved between a high concentration of sorbed monomer and a low viscosity for the poorly swelled polymer matrix.