The Role of Hydrogen Bond and Crystal Solvent in the Solid-state (β-α) Photoisomerization of Novel 2-(N-phenylcarbamoyl)ethyl Cobaloxime Complexes [1]

Abstract

The 2-(phenylcarbamoyl)ethyl group bonded to the cobalt atom in cobaloxime complexes was isomerized on exposure to visible light in the solid-state. The three complexes with different amines as axial base ligands were prepared and their crystal structures were determined by X-ray analysis. The reaction rates in the solid-state were mainly affected by the hydrogen bonds of the reactive group with the neighboring molecules and the occupation of crystal solvent molecules around the reactive group.     

Heavy element stable isotope ratios : analytical approaches and applications

Continuous developments in inorganic mass spectrometry techniques, including a combination of an inductively coupled plasma ion source and a magnetic sector-based mass spectrometer equipped with a multiple-collector array, have revolutionized the precision of isotope ratio measurements, and applications of inorganic mass spectrometry for biochemistry, geochemistry, and marine chemistry are beginning to appear on the horizon. Series of pioneering studies have revealed that natural stable isotope fractionations of many elements heavier than S (e.g., Fe, Cu, Zn, Sr, Ce, Nd, Mo, Cd, W, Tl, and U) are common on Earth, and it had been widely recognized that most physicochemical reactions or biochemical processes induce mass-dependent isotope fractionation. The variations in isotope ratios of the heavy elements can provide new insights into past and present biochemical and geochemical processes. To achieve this, the analytical community is actively solving problems such as spectral interference, mass discrimination drift, chemical separation and purification, and reduction of the contamination of analytes. This article describes data calibration and standardization protocols to allow interlaboratory comparisons or to maintain traceability of data, and basic principles of isotope fractionation in nature, together with high-selectivity and high-yield chemical separation and purification techniques for stable isotope studies.

High-contrast, high-intensity laser pulse generation using a nonlinear preamplifier in a Ti:sapphire laser system

We report a high-contrast, high-intensity Ti:sapphire chirped-pulse amplification system that incorporates a nonlinear preamplifier based on optical parametric chirped-pulse amplification (OPCPA). By cooling the Ti:sapphire crystal in the final amplifier down to 77 K, the chirped-pulses are amplified to 2.9 J at a 10 Hz repetition rate without a thermal lensing effect. Pulse compression down to 19 fs duration obtained after amplification indicates a peak power of 80 TW. With the OPCPA, the temporal contrast is significantly improved to better than 7x10(-9) in a few picoseconds interval prior to the main laser pulse.     

Order-disorder phase transition in a chaotic system

For soft-mode turbulence, which is essentially the spatiotemporal chaos caused by the nonlinear interaction between convective modes and Goldstone modes in electroconvection of homeotropic nematics, a type of order-disorder phase transition was revealed, in which a new order parameter was introduced as pattern ordering. We calculated the spatial correlation function and the anisotropy of the convective patterns as a 2D XY system because the convective wave vector could freely rotate in the homeotropic system. We found the hidden order in the chaotic patterns observed beyond the Lifshitz frequency f(L), and a transition from a disordered to a hidden ordered state occurred at the f(L) with the increase of the frequency of the applied voltages.     

J/psi production in sqrt s_NN=200 GeV Cu+Cu collisions

Yields for J/psi production in Cu+Cu collisions at sqrt s_NN=200 GeV have been measured over the rapidity range |y|<2.2 and compared with results in p+p and Au+Au collisions at the same energy. The Cu+Cu data offer greatly improved precision over existing Au+Au data for J/psi production in collisions with small to intermediate numbers of participants, in the range where the quark-gluon plasma transition threshold is predicted to lie. Cold nuclear matter estimates based on ad hoc fits to d+Au data describe the Cu+Cu data up to N_part approximately 50, corresponding to a Bjorken energy density of at least 1.5 GeV/fm(3).     

Kinetics of Si2H2 produced by the 193 nm photolysis of disilane

Si₂H₂ species were produced through the 193 nm excimer laser photolysis of Si₂H₆. Time‐resolved photoionization mass spectrometry was employed to study the reaction kinetics of Si₂H₂. The lower limit of self‐reaction of Si₂H₂ was estimated, k(Si₂H₂ + Si₂H₂) ≥ (1.7 ± 0.5) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹, through analysis of the decay traces. This rate constant was independent of a total pressure on the entire pressure range (p_total = 1–7 Torr). No reaction of Si₂H₂ with H₂, CH₄, SiH₄, and Si₂H₆ was confirmed. The decay rates of Si₂H₂ reacting with O₂, NO, and HCl exhibit negative dependence on the total pressure. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 136–141, 2001     

Synthesis of poly(cyclodiborazane)s by allylboration polymerization of dicyano compounds with trimethallylborane

Allylboration polymerization of α, ω-dicyanoalkanes with trimethallylborane produced the corresponding poly(cyclodiborazane)s in high yields. This polymerization includes the allylboration reaction of cyano groups and the following dimerization of iminoborane species. The intermediate iminoborane species were detected by IR measurement. The poly(cyclodiborazane)s obtained were found to be more stable toward air than those prepared by allylboration polymerization using triallylborane.     

Lewis-Pairing-Induced Electrochemiluminescence Enhancement from Electron Donor-Acceptor Diads Decorated with Tris(pentafluorophenyl)borane as an Electrochemical Protector

This study reports an effective peripheral decoration of organic donor-acceptor diads with B(C₆F₅)₃ for stabilizing electrogenerated radical ions. By employing a common p-type organic semiconductor benzothienobenzothiophene (BTBT) as the donor, tetracoordinate boron complexes showed improved solution electrochemiluminescence (ECL) intensity, reaching a 156-fold increase compared to that of the parent diad. The unprecedented Lewis-pairing-induced ECL enhancement is attributed to the multiple roles of B(C₆F₅)₃: 1) redistributing frontier orbitals, 2) facilitating electrochemical excitation, and 3) restricting molecular motions. Furthermore, B(C₆F₅)₃ converted the molecular arrangement of BTBT from conventional 2D herringbones into 1D π-stacks. This robust, highly ordered columnar nanostructure allowed red-shifting of the crystalline film ECL with electrochemical doping through the electronic coupling pathways of BTBT. Our approach will facilitate the development of elaborate metal-free ECL systems.     

Synthesis of well-defined azido and amino end-functionalized polystyrene by atom transfer radical polymerization

Mono and difunctional polystyrenes containing active halogenated end groups were prepared by atom transfer radical polymerization (ATRP). Substitution reactions were explored to convert the halogen termini to azido groups, followed by readuction to form the amino functional polymer. Quantitative conversion of the end groups was observed in each transformation reaction. ¹H NMR demonstrated the formation of the azide from the bromide functionality without elimination. The difunctional α,ω-diaminopolystyrene was reacted with terephthaloyl chloride in a condensation process to produce chain-extended polystyrene containing amide bonds along the polymer backbone.