Recent developments in heterocyclic systems with a Si–M′–Ge or Ge–M′–Ge linkage (M′ = Fe,Ru, or Co)

The present review describes recent work on the synthesis, spectroscopic analysis, and investigation of the chemical behaviors of new polynuclear heterocyclic complexes 1–7 having M–M′–M catenation. Various CO substitution, cleavage, expansion, and adducts decomposition reactions are described.     

Enhancement of inhomogeneities in gels upon swelling and stretching

In this paper, it is shown how a percolation process can be used to describe the inhomogeneities of polymer concentration, appearing in gels prepared by random crosslinking of a semi-dilute solution, and how they are modified by swelling or stretching of the network. Neutron scattering experimental data are compared to the predictions of this model in the isotropic and anisotropic cases. A good agreement is found. In particular, “abnormal” butterfly patterns in the iso-intensity curves have been detected, as expected from the model.     

Chemometrics in chromatography

The impact of chemometrics in chromatography is presented. The development of systematic experiments is encouraged to exploit simultaneously the richness of teh chromatographic data and the possibilities of complementary data processing techniques.     

Expedient BINOL derivative arylations

A dramatic improvement of our previous methodology based on a Suzuki–Miyaura cross-coupling to access 3,3′-disubstituted H₈-BINOLs using microwave heating is reported herein. These new conditions represent a large gain in term of atom-economy, reaction time, catalyst loading, and excess of reagents employed.     

Electrical Conductivity in TCNQ Salts of Bis(4-dimethylaminophenylimino) sulfur and its Structural Analogues

Four compounds, N,N,N',N'-tetramethyl-p-phenylene diamine, N,N,N',N'-tetramethyl-benzidine, 4,4'-bis(dimethylamino)azobenzene and bis(4-dimethylaminophenylimino)sulfur (BAPIS) were examined electrochemically and spectroscopically. Each was shown to be a fairly good donor forming in its first oxidation state a radical-cation. The latter two materials surprisingly exhibited only single one-electron oxidations. Conformational flexibility about the -NSN- unit was studied by NMR spectroscopy and ab initio molecular orbital theory. The experimental ΔG* for a cis-trans to trans-cis interconversion in BAPIS was found to be 11.9 kcal/mole.

The four donors all form 1:1 adducts with TCNQ. The compaction resistances of the complexes have been measured as a function of temperature. Of the four, (BAPIS)(TCNQ) appears to be a one-dimensional material. The other three complexes behave as typical mixed stack organic semiconductors.     

Anisotropic surface effects in Au and Cu monocrystals

Electroreflectance spectra at normal incidence of (100) and (110) faces of gold and copper monocrystals are given, in the spectral range from 0.22–0.7 μm. The fractional change in reflectance is different with (110) faces when light is polarized parallel to the [001] direction and parallel to the [$\text{1}\text{10}$] direction while no anisotropy is seen on (100) faces. This shows that electroreflectance is a powerful tool to investigate metal surfaces where the optical electrons are sensitive to the distribution of the surface atoms.     

Spin asymmetry in γe ↑→e+2 jets: A laboratory for final state interactions

We isolate final state interactions not parametrized by fragmentation functions and yet present in QCDO(α _s ) corrections to two-jet production in photon-longitudinally polarized electron scattering. Our calculation focuses on dynamical imaginary (absorptive) corrections that are absent in any tree diagrams. We explicitly demonstrate cancellation of imaginary infinities in the sum over graphs. The resulting asymmetry is predicted to be small. Such a quantity should be soon measured in experiments exploiting the naturally large electron polarization occurring in standard high energy storage rings.     

Probing Proteins in Solution by Xe NMR Spectroscopy

The interaction of xenon with different proteins in aqueous solution is investigated by ¹²⁹Xe NMR spectroscopy. Chemical shifts are measured in horse metmyoglobin, hen egg white lysozyme, and horse cytochrome c solutions as a function of xenon concentration. In these systems, xenon is in fast exchange between all possible environments. The results suggest that nonspecific interactions exist between xenon and the protein exteriors and the data are analyzed in term of parameters which characterize the protein surfaces. The experimental data for horse metmyoglobin are interpreted using a model in which xenon forms a 1:1 complex with the protein and the chemical shift of the complexed xenon is reported (Locci et al., Keystone Symposia “Frontiers of NMR in Molecular Biology VI”, Jan. 9–15, 1999, Breckenridge, CO, Abstract E216, p. 53; Locci et al., XeMAT 2000 “Optical Polarization and Xenon NMR of Materials”, June 28–30, 2000, Sestri Levante, Italy, p. 46).     

Photophysics of Calix[4]biscrown-Based Ditopic Receptors of Caesium Containing One or Two Dioxocoumarin Fluorophores

The ditopic receptors Calix-COU1 and Calix-COU2 consist of a calix[4]biscrown containing one or two dioxycoumarin fluorophores, respectively, inserted into the crown. They can form 1:1 and 2:1 (metal:ligand) complexes with caesium ions. The photophysical properties of the 1:1 complexes can be explained by (i) cation tunneling through the tube-shaped cavity (composed of the four phenyl rings) of the calix[4]biscrown, (ii) photodisruption of the interaction between the bound cation and the oxygen atoms belonging to both the coumarin moiety and the crown, (iii) photoinduced motions of the cation.     

Chemical modification of poly(lactic acid) induced by thermal decomposition of N‐acetoxy‐phthalimide during extrusion

Chemical modification of poly(lactic acid) (PLA) with N‐acetoxy‐phthalimide (NAPI) was performed in the melt by reactive extrusion, without using any peroxide initiator. The aminyl and nitroxide radicals produced from the NAPI thermal degradation, were, respectively, used (a) to create PLA macroradicals, and (b) to functionalize the PLA samples through nitroxide radical coupling. Depending on the extrusion temperature and the initial NAPI concentration, grafting rates up to 0.24 mol % were measured, modifying the PLA optical properties. This study represents an original new way of modification of PLA without the use of conventional peroxide initiators. Indeed, the undesirable side reactions (PLA branching or crosslinking) usually observed when using peroxides to initiate the radical grafting of PLA were avoided when using NAPI. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 120–129