Crystallization Mechanism of 9,9-Diphenyl-dibenzosilole from Solids

Organic semiconductor (OSC) crystals have great potential to be applied in many fields, as they can be flexibly designed according to the demands and show an outstanding device performance. However, OSCs with the capacity of solid-state crystallization (SSC) are developing too slowly to meet demands in productions and applications, due to their difficulties in molecular design and synthesis, unclear mechanism and high dependence on experimental conditions. In this work, in order to solve the problems, we synthesized an organic semiconductor capable of SSC at room temperature by adjusting the relationship between conjugated groups and functional groups. The thermodynamic and kinetic properties have been studied to discover the model of film SSC. Moreover, it can be purposefully controlled to prepare the high-quality crystals, and their corresponding organic electronic devices were further fabricated and discussed.     

Enhanced Photochromism of Diarylethene Induced by Excitation of Localized Surface Plasmon Resonance on Regular Arrays of Gold Nanoparticles

Localized surface plasmon resonance (LSPR) excitation on the photochromic reaction of a diarylethene derivative (DE) was studied by surface enhanced Raman scattering (SERS). UV and visible light irradiations transform reversibly DE between open-form (OF) and closed-form (CF) isomers, respectively. A mixture of PMMA and DE (either OF or CF isomer) was spin-coated onto gold nanorods (GNRs) arrays, designed by electron beam lithography, with two localized surface plasmon resonances (LSPR) at distinct wavelengths, due to their anisotropy. The photochromic reaction rates from CF to OF isomers, under LSPR excitation, were monitored from SERS spectral changes under different polarizations, on the same GNR substrate to compare the effect of LSPR field strength. It appears that the photoisomerization rate was faster when LSPR was excited with the polarization parallel to the GNR long axis. The present results highlight a potential genuine mechanism, from near field LSPR excitation, involved in the photochromic enhancement of diarylethene photochromes.     

Targeting the Rich Conformational Landscape of N-Allylmethylamine Using Rotational Spectroscopy and Quantum Mechanical Calculations

The highly variable conformational landscape of N-allylmethylamine (AMA) was investigated using Fourier transform microwave spectroscopy aided by high-level theoretical calculations to understand the energy relationship governing the interconversion between nine stable conformers. Spectroscopically, transitions belonging to four low energy conformers were identified and their hyperfine patterns owing to the ¹⁴N quadrupolar nucleus were unambiguously resolved. The rotational spectrum of the global minimum geometry, conformer I, shows an additional splitting associated with a tunneling motion through an energy barrier interconnecting its enantiomeric forms. A two-step tunneling trajectory is proposed by finding transition state structures corresponding to the allyl torsion and NH inversion. Natural bond orbital and non-covalent interaction analyses reveal that an interplay between steric and hyperconjugative effects rules the conformational preferences of AMA.     

Stabilization of the Closed-Ring Isomer of Spiropyran by Amide Naphthotube in Water and Its Application in Naked-Eye Detection of Toxic Paraoxon

The thermodynamically unstable, colourless closed-ring isomer of spiropyran can be stabilized in water by the anti-configurational isomer of amide naphthotube. The influence of the binding on the thermodynamics and kinetics of spiropyran have been studied. The complex was further used to prepare a test paper that allows naked-eye detection of toxic paraoxon.     

Ab initio SCF structure investigation of β-hydroxypropionic acid and 3-aminopropionamide

The potential energy surfaces of β-hydroxypropionic acid and 3-aminopropionamide have been investigated by means of RHF /4-31G calculations. Structures, reaction paths for internal rotations, and the respective energy barriers are reported. The influence of the various intramolecular interactions on structural and energetical properties is shown and compared to the results previously obtained for β-alanine. © 1996 John Wiley & Sons, Inc.     

A shock tube study of the reactions of CH with CO2 and O2

The formation and consumption of CH radicals during shock-induced pyrolysis of a few ppm ethane diluted in argon was measured by a ring-dye laser spectrometer. Absorption-over-time profiles, measured at a resonance line in the Q-branch of the A²Δ − X²Π band of CH at λ = 431.1311 nm, were recorded and transformed into CH concentrations by known absorption coefficients. By adding some hundred ppm of CO₂ or O₂ to the initial mixtures, the CH concentration profiles were significantly perturbed. Both the perturbed and unperturbed CH concentration profiles have been compared with calculations based on a reaction kinetic model. A sensitivity analysis revealed that the perturbation process was dominated by direct reactions of CH with the added molecules. By fitting calculated to observed CH profiles the following rate coefficients were obtained The experiments were performed in the temperature range between 2500 K and 3500 K. © 1996 John Wiley & Sons, Inc.     

Third-order Nonlinear Optical Properties of Octa-substituted Metal-free Phthalocyanine Thin Films

Third-order nonlinear optical susceptibility, χ⁽³⁾ of symmetrically octa-substituted metal-free phthalocyanine thin films measured by the third-harmonic generation technique are reported. The metal-free phthalocyanine has been found to show a χ⁽³⁾ (−3ω; ω,ω, ω) value as large as 7.73×10⁻¹² esu at 1.80 μm. The figure of merit, χ⁽³⁾/α, was estimated to be 4.17×10¹⁷ esu cm at 1.05 μm and 6.97×10¹⁶ esu cm at 1.65 μm. Both linear and third-order optical properties of liquid-crystalline metal-free phthalocyanines are discussed     

Synthesis of Oligomeric Axially Bridged Ruthenium Phthalocyanines and 2,3-Naphthalocyanines

Bridged 2,3-naphthalocyaninatoruthenium oligomers {[MacRu(L)] _n } were synthesized and characterized using solid-state methods. For comparison, soluble t-butyl substituted phthalocyaninatoruthenium oligomers were prepared and their chain length examined by ¹H NMR spectroscopy. The powder conductivities of all bridged compounds ([MacRu(L)] _n ) were measured and the dependence of the conductivities on the bridging ligands is discussed.     

Comparison of electron spin resonance probe and dielectric relaxation in physically and chemically crosslinked polymers

Dielectric relaxation spectroscopy in the frequency range from 10⁻² Hz to 10⁶ Hz and electron spin resonance (ESR) experiments are employed to study the dynamics in chemically and physically crosslinked networks. As examples for physically crosslinked networks ortho- and para-cresol novolacs were investigated. Dielectrically these materials show low-temperature β- and high-temperature α-relaxation. Both relaxation regions differ for both types of novolacs. This is also reflected by the ESR measurements and is discussed in terms of different hydrogen bonds found to be stronger in para-cresol novolac. For the chemically crosslinked poly(triallyl isocyanurate) only a β-peak is found by the dielectric measurements. Also in the ESR experiment the slow motion regime is characterized up to high temperatures. This means that the segmental motion is strongly suppressed by chemical crosslinking. Nevertheless the obtained change in the formal T_50G value can be used to characterize the glass transition in highly crosslinked systems by the ESR method.