Electronic delocalization in discotic liquid crystals: a joint experimental and theoretical study

Discotic liquid crystals emerge as very attractive materials for organic-based (opto)electronics as they allow efficient charge and energy transport along self-organized molecular columns. Here, angle-resolved photoelectron spectroscopy (ARUPS) is used to investigate the electronic structure and supramolecular organization of the discotic molecule, hexakis(hexylthio)diquinoxalino[2,3-a:2',3'-c]phenazine, deposited on graphite. The ARUPS data reveal significant changes in the electronic properties when going from disordered to columnar phases, the main feature being a decrease in ionization potential by 1.8 eV following the appearance of new electronic states at low binding energy. This evolution is rationalized by quantum-chemical calculations performed on model stacks containing from two to six molecules, which illustrate the formation of a quasi-band structure with Bloch-like orbitals delocalized over several molecules in the column. The ARUPS data also point to an energy dispersion of the upper pi-bands in the columns by some 1.1 eV, therefore highlighting the strongly delocalized nature of the pi-electrons along the discotic stacks.     

Effect of (3‐glycidyloxypropyl)trimethoxysilane (GOPS) on the electrical properties of PEDOT:PSS films

Poly(3,4‐ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) has been reported as a successful functional material in a broad variety of applications. One of the most important advantages of PEDOT:PSS is its water‐solubility, which enables simple and environmental friendly manufacturing processes. Unfortunately, this also implies that pristine PEDOT:PSS films are unsuitable for applications in aqueous environments. To reach stability in polar solvents, (3‐glycidyloxypropyl)trimethoxysilane (GOPS) is typically used to cross‐link PEDOT:PSS. Although this strategy is widely used, its mechanism and effect on PEDOT:PSS performance have not been articulated yet. Here, we present a broad study that provides a better understanding of the effect of GOPS on the electrical and electronic properties of PEDOT:PSS. We show that the GOPS reacts with the sulfonic acid group of the excess PSS, causing a change in the PEDOT:PSS film morphology, while the oxidation level of PEDOT remains unaffected. This is at the origin of the observed conductivity changes. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 814–820     

Bis(allyl)zinc revisited: sigma versus pi bonding of allyl coordination

The reinvestigation of two allyl zinc compounds, parent bis(allyl)zinc [Zn(C(3)H(5))(2)] (1) and 2-methallyl chloro zinc [Zn(C(4)H(7))Cl] (2), revealed two new coordination modes in the solid state for the allyl ligand, viz cis- and trans-μ(2)-η(1):η(1). These results call for modification of the conventional interpretation of zinc-allyl interactions. Computational results indicate that the classical η(3)-bonding mode of the allyl ligand is not favored in zinc compounds. A rare case of a zinc-olefin interaction in the dimer of [Zn(η(1)-C(3)H(5))(OC(C(3)H(5))Ph(2))] was found in the monoinsertion product of 1 with benzophenone.     

Vertical symbols,Toeplitz operators on weighted Bergman spaces over the upper half-plane and very slowly oscillating functions

Extending a recent result of Herrera Yañez, Maximenko and Vasilevski, we provide a further step in the structural analysis of algebras generated by Toeplitz operators on weighted Bergman spaces over the upper half-plane. We show that the set of “spectral” functions corresponding to Toeplitz operators generated by bounded vertical symbols is dense in the C^?$C^{?}$-algebra of very slowly oscillating functions on the positive half-line.     

Double CH Activation of a Masked Cationic Bismuth Amide

The transformation of C?H bonds into more reactive C?M bonds amenable to further functionalization is of fundamental importance in synthetic chemistry. We demonstrate here that the transformation of neutral bismuth compounds into their cationic analogues can be used as a strategy to facilitate CH activation reactions. In particular, the double CH activation of bismuth‐bound diphenyl amide, (NPh₂)^?, is reported along with simple one‐pot procedures for the functionalization of the activated positions. The organometallic products of the first and second CH activation steps were isolated in high yields. Analysis by NMR spectroscopy, single‐crystal X‐ray diffraction, and DFT calculations revealed unusual ground‐state properties (e.g., ring strain, moderate heteroaromaticity), and provided mechanistic insight into the formation of these compounds.     

Second-order properties of bonds

By defining a localized hamiltonian for a saturated molecule its second order molecular properties may be regarded as a sum of bond contributions. Static and dynamic polarizabilities are calculated for the CH bond in methane and the latter one used to calculate the van der Waals interaction between two CH₄ molecules.     

Differentiation between isomeric triantennary N-linked glycans by negative ion tandem mass spectrometry and confirmation of glycans containing galactose attached to the bisecting (beta1-4-GlcNAc) residue in N-glycans from IgG

Negative ion tandem mass spectrometry (MS/MS) spectra of three isomeric triantennary N-linked glycans provided clear differentiation between the isomers and confirmed the occurrence of an isomer that was substituted with galactose on a bisecting GlcNAc (1 --> 4-substituted on the core mannose) residue recently reported by Takegawa et al. from N-glycans released from human immunoglobulin G (IgG). We extend this analysis of human serum IgG to reveal an analogue of the fucosylated triantennary glycan reported by Takegawa et al. together with a third compound that lacked both the sialic acid and the fucose residues. In addition, we demonstrate the biosynthesis of bisected hybrid-type glycans with the galactose modification, with and without core fucose, on the stem cell marker glycoprotein, 19A, expressed in a partially ricin-resistant human embryonic kidney cell line. It would appear, therefore, that this modification of N-linked glycans containing a galactosylated bisecting GlcNAc residue may be more common than originally thought. Negative ion MS/MS analysis of glycans is likely to prove an invaluable tool in the analysis and monitoring of therapeutic glycoproteins.     

New reactive polymeric systems for use as waveguide materials in integrated optics

Cross-linked polymeric materials are used in a wide range of applications. Special compositions are used in micro-system technologies and its utilization is extending to integrated optics. We have been working for several years in the field of polymers for optical applications. Highly fluorinated polycyanurate systems have been proven as promising waveguide materials in integrated optics. The refractive index can be adjusted reproducibly in a wide range almost continuously. The layer quality was optimized. Low optical losses of less than 0.3 dB/cm@1550nm were obtained and working optical prototypes were developed. The birefringence had been a major problem, but this was solved by adjusting the coefficient of thermal expansion of substrate and film. We will report in this paper on the polycyanurate ester resins and the new triazine containing polymeric systems.