Donor‐Embedded Polybinaphthalenes for Nonlinear Optical Applications: Influence of the Incorporation of a Double Bond

Summary: In this paper two new donor‐embedded polybinaphthalenes prepared by the Heck reaction are presented. By introducing a double bond in the polymer backbone, the supramolecular structure was altered in comparison with polymers without the double bond. Comparison between the CD/UV‐Vis spectra of polymers, with and without the double bond (previously synthesized in our laboratory) proved this change in a supramolecular structure. The double bonds also allow crosslinking upon heat treatment. NLO experiments demonstrated a more stable nonlinearity over time depending on the degree of crosslinking.

     

Organometallic complexes for nonlinear optics: Part 21. Syntheses and quadratic hyperpolarizabilities of alkynyl complexes containing optically active 1,2-bis(methylphenylphosphino)benzene ligands

The preparation of the chloro complex trans-[FeCl₂{(R,R)-diph}₂] (1) and the alkynyl complexes trans-[M(4-CCC₆H₄R)Cl{(R,R)-diph}₂] [M=Fe, R=NO₂ (2); M=Ru, R=H (4), NO₂ (5), (E)-CH=CH-4-C₆H₄NO₂ (6); M=Os, R=NO₂ (7)], incorporating the optically active diphosphine 1,2-bis(methylphenylphosphino)benzene (diph), are described. Oxidation potentials, as determined by cyclic voltammetry, increase as 2<7<5. Molecular quadratic nonlinearities by hyper-Rayleigh scattering at 1064 nm increase upon introduction of an acceptor group (4<5), chain-lengthening of bridging group (5<6), and proceeding from 3d to 4d and 5d metal (2≤5≤7). Two-level-corrected nonlinearities reproduce the first two trends, but metal variation follows the sequence 2<7<5. The experimental and two-level-corrected nonlinearities for 6 (2795×10⁻³⁰ and 406×10⁻³⁰ esu, respectively), are amongst the largest observed thus far for organometallic complexes. Crystals of complexes 2 and 7 exhibit second-harmonic generation (assessed using the Kurtz powder technique), with an efficiency for the former of twice that of urea.     

Hydrodynamic properties and conformation of poly(3‐hexylthiophene) in dilute solutions

Conducting polymers demonstrate low solubility in organic solvents. Introducing aliphatic substituents into polymer chains improves their solubility, but may also lead to changes in conformational characteristics of macromolecules. In the present work, the studies of hydrodynamic properties and conformational characteristics of comb‐shaped poly(3‐hexylthiophene) with aliphatic side substituents were carried out in chloroform solutions. Conformational analysis of the studied macromolecules was performed for the first time using homologous series with a wide range of molecular weights of the polymers in dilute solutions. The hydrodynamic properties of these macromolecules were interpreted using the worm‐like spherocylinder model and the straight spherocylinder model. The projection of the monomer unit in the direction of the main polymer chain λ = 0.37 nm was determined experimentally. The following parameters of poly(3‐hexylthiophene) were characterized and quantified: equilibrium rigidity (Kuhn segment length) А = 6.7 nm and hydrodynamic diameter of a polymer chain d = 0.6 nm. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 875–883     

Microwave absorption studies of MgB2 superconductor

Microwave absorption studies have been carried out on MgB₂ superconductor using a standard X-band EPR spectrometer. The modulated low-field microwave absorption signals recorded for polycrystalline (grain size ∼ 10 μm) samples suggested the absence of weak-link character. The field dependent direct microwave absorption has been found to obey a ✓H dependence with two different slopes, which indicated a transition from strongly pinned lattice to flux flow regime.     

The FT-IR study of the brain tissue of Labeo rohita due to arsenic intoxication

The brain is believed to be particularly vulnerable to arsenic due to its high oxygen consumption rate and high level of polyunsaturated fatty acids and relatively high rate of oxygen free radical generate without commensurable level of arsenic. Hence, in the present work an attempt is made to study the changes in the biochemical contents in the brain tissues of edible fish Labeo rohita due to arsenic intoxication using Fourier Transform Infrared (FT-IR) spectroscopy. FT-IR spectra reveal significant differences in absorbance intensities between the control and arsenic intoxicated brain tissues, reflecting an alteration on the major biochemical constituents, such as lipids, proteins and nucleic acids of the brain tissues of L. rohita due to arsenic intoxication. Further, the administration of antidote DMSA improves the protein and lipid contents significantly in the brain tissues when compared to arsenic intoxicated tissues. The decrease in α-helix structure due to arsenic intoxication might be responsible for the increase in β-sheet secondary structures, which is consistent with the mechanism of β-sheet formation.     

Efficient,Reversible Redox‐Switching of Molecular First Hyperpolarizabilities in Ruthenium(II) Complexes Possessing Large Quadratic Optical Nonlinearities

Low‐energy metal‐to‐ligand charge‐transfer (MLCT) excitations are associated with the very large molecular nonlinear optical (NLO) coefficients, β, of the complexes [Ru^II(NH₃)₅(N‐R‐4,4′‐bipyridinium)]³⁺ (R=methyl, phenyl, or 4‐acetylphenyl). Chemical oxidation to the Ru^III forms causes bleaching of the MLCT absorptions and marked attenuation of the NLO responses. Both effects are completely reversed upon re‐reduction, and the extent of the β switching is about 10‐ to 20‐fold.     

Routine analysis by high precision gas chromatography/mass selective detector/isotope ratio mass spectrometry to 0.1 parts per mil

Stable isotope methods are potentially quite useful for validating natural or enhanced mineral degradation of contaminants. For this reason, a continuous flow gas chromatograph (GC), isotope ratio mass spectrometer (IRMS) has been coupled with a quadrupole mass selective detector (MSD) to allow simultaneous mass spectral and stable carbon isotope ratio data to be obtained from a single chromatographic analysis. This allows the target contaminant and any extra-cellular degradation intermediates to be both qualified and quantified. Previously acceptable limits of precision (0.3 parts per mil) are undesirable given the small fractionation observed during aerobic degradation. To further understand the fate of organic contaminants and to gain information about the metabolic degradative pathway employed by a microorganism, routine isotopic analyses on a range of analytes have been performed. Quantities of sample producing mass-44 ion beam signal (I(44)) of 2 x 10(-10) to 1 x 10(-8) A were analysed. When the IRMS was tuned for high sensitivity, ion source nonlinearities were overcome by peak height correction from an algorithm that was produced using known isotopic standards of varying concentrations. This led to sample accuracy of <0.01 per thousand and sample precision of 0.1 per thousand. Copyright 1999 John Wiley & Sons, Ltd.