Synthesis of selectively deuterated fulvenes and indenes from enediynes

A facile enediyne--> fulvene--> indene transformation provides a route to all possible isotopomers of substituted fulvenes and indenes.     

How important is the dispersion interaction for cyclobis(paraquat‐p‐phenylene)‐based molecular “shuttles”? A theoretical study

Inclusion complexes of cyclobis(paraquat‐p‐phenylene) and various aromatic molecules in their neutral and oxidized form were studied at the LMP2/6‐311+G**//BHandHLYP/6‐31G* level of theory, which represents the highest level theoretical study to date for these complexes. The results show that it is dispersion interaction that contributes most to the binding energy. One electron oxidation of a guest molecule leads to complete dissociation of inclusion complex generating strong repulsion potential between guest and host molecules. Electrostatic interactions also can play an important role, provided the guest molecule has a dipole moment; however, dispersion interactions always dominate in binding energy. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Exchange interactions in oxovanadium phosphates: towards the understanding of the magnetic patterns

We report the calculations of exchange magnetic constants in a series of vanadium phosphorus oxides for which structural and magneto-chemical data are available. Four different types of dimers have been extracted from the crystal lattices in all solids studied. On the basis of a combined density functional theory broken symmetry approach, our calculations on molecular models allow us to define schemes of magnetic interactions. The largest absolute magnetic interaction is provided by the double O–P–O and di-μ-oxo bridges, suggestive of an alternating dimer chain model and an isolated dimer one for the VO(HPO₄)·0.5H₂O and α-VO(HPO₄)·2H₂O phases, respectively. Conversely, VO(HPO₄)·4H₂O is consistent with a bi-dimensional magnetic pattern whereas VO(H₂PO₄)₂ and α-VO(PO₃)₂ with three-dimensional magnetic schemes. The use of dimer models has been justified by the analysis of higher-nuclearity clusters.     

Determination of anisotropic optical constants and surface coverage of molecular films using polarized visible ATR spectroscopy. Application to adsorbed cytochrome c films

This article describes a method to determine the anisotropic optical constants and surface coverage of molecular films using polarized attenuated total reflectance (ATR) absorbance measurements. We have extended the transfer-matrix formalism to describe birefringent and dichroic films in ATR geometries and have combined it with an iterative numerical procedure to determine the anisotropic values of both the real (n) and imaginary (k) parts of the complex refractive index of the film under investigation. Anisotropic values of the imaginary part of the refractive index (k) allow for the determination of the surface coverage and one order parameter of the film. To illustrate this approach, we have used cytochrome c (cyt c) protein films adsorbed to glass and indium tin oxide (ITO) surfaces. Experimental results show that cyt c films on these surfaces, which were formed under identical conditions, have significant differences in their surface coverages (11.2 +/- 0.4 pmol/cm(2) on glass and 21.7 +/- 0.9 pmol/cm(2) on ITO); however, their order parameters are similar (0.30 +/- 0.02 on glass and 0.36 +/- 0.04 on ITO).     

Asymptotically sharp uniform estimates in a scalar spectral stiff problemEstimations asymptotiques uniformes pour le spectre d'un problème scalaire raide

Estimates of convergence rates for rescaled eigenvalues of the stiff Neumann problem for the Laplacian are obtained. The bounds are expressed in terms of the stiffness ratio and properties of the limit spectrum both for low and middle frequency ranges. To cite this article: M. Lobo et al., C. R. Mecanique 331 (2003).     

Upper limit on the solar antineutrino flux according to LSD data

The experimental data obtained on the liquid scintillation detector LSD are analyzed for the purpose of searching for the solar electron antineutrino flux predicted in the model of spin-flavor precession of the neutrino. The currently most accurate upper limit on the solar v̄_e/v _e flux ratio is established: Φ_v̄/Φ_v⩽1.7% (90% confidence range). Pis’ma Zh. éksp. Teor. Fiz. 63, No. 10, 753–757 (25 May 1996) The spelling of the authors names are presented here in English as requested by the Russian Editorial office.     

Synthesis and optical characterization of photoactive poly(2‐phenoxyethyl acrylate) copolymers containing azobenzene units,prepared by frontal polymerization using novel ionic liquids as initiators

2‐Phenoxyethyl acrylate (2‐PEA) was polymerized alone and in the presence of an azobenzene comonomer derived from Disperse Red‐1, N‐ethyl‐N‐(2‐hydroxyethyl)‐4‐(4‐nitrophenylazo)aniline (MDR‐1), by using the frontal polymerization technique. Two novel ionic liquids, recently synthesized by us, were used as initiators: tetrabutylphosphonium persulfate (TBPPS) and trihexyltetradecylphosphonium persulfate (TETDPPS). Even if their concentrations were smaller than those found when benzoyl peroxide and terbutylperoxy neodecanoate were used, these compounds gave rise to stable propagating polymerization fronts characterized by relatively low maximum temperatures and good velocities. Moreover, at variance to these latter, TBPPS and TETDPPS prevent bubble formation, thus allowing the use of the obtained materials in optical applications. The obtained polymers were characterized by infrared spectroscopy (FTIR), their thermal properties were determined by differential scanning calorimetry, and their optical properties were studied by absorption spectroscopy in the UV–vis region. Finally, the nonlinear optical (NLO) properties of the 2‐PEA/MDR‐1 copolymers obtained with TBPPS and TETDPPS were performed according to the Z‐Scan technique with prepared film samples. It has been proven that samples with higher MDR‐1 content (0.05 mol %) exhibited outstanding cubic NLO activity with negative NLO refractive coefficients around n₂ = ?1.7 × 10^?3 esu. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012