Quantum tunneling in hydrogen transfer reactions active in FRP is investigated theoretically. Three systems are examined: polyethylene, polystyrene, and poly(vinyl chloride). Kinetic parameters of backbiting reactions are evaluated adopting quantum chemistry. Tunneling corrections are estimated adopting the one‐dimensional Eckart model, which provides a reasonable accuracy along with a limited computational effort. The relevance of quantum tunneling in the investigated systems is highlighted, with focus on the temperature dependence of the tunneling correction in the typical polymerization conditions of the investigated monomers. Obtained results clearly show that tunneling plays an important role in the kinetics estimation of hydrogen abstractions in FRP.
This work gives an overview concerning the optical limiting processes in phthalocyanines. In particular, the synthesis and the relevant optical properties of a series of axially substituted indium(III)− and titanium(IV)−phthalo- and -naphthalocyanines are described. Several techniques, such as transient absorption, Z-scan, and degenerate four-wave mixing, have been used for assessing the optical properties and optical limiting performance of the investigated compounds. 相似文献
A facile synthesis of highly soluble, axially substituted titanium(IV ) phthalocyanines is described. The reaction of tetra-tert-butylphthalocyaninatotitanium oxide tBu4PcTiO with the chelating agents 3a − 3i containing oxygen or sulfur as donor atoms leads to the formation of axially substituted tBu4PcTiX (X = functionalized catechols, dithiocatechol, and dihydroxynaphthalene). Following the same procedure a dimeric sandwich-like complex could be also synthesized from the reaction of tBu4PcTiO with tetrahydroxy-p-benzoquinone. All compounds were characterized by IR, UV/Vis, MS, 1H and 13C NMR spectroscopy, and elemental analysis. The axially substituted titanium phthalocyanines show high solubility and a low aggregation tendency due to the steric hindrance arising from the asymmetric peripheral substitution pattern of the macrocycle and the presence of bulky axial ligands. The relevant nonlinear optical (NLO) properties of some of the tBu4PcTiX compounds were determined in order to evaluate the potential role of these new compounds in optical limiting. The correlation between tBu4PcTiX structure and NLO properties is analyzed in terms of the electronic effects of the axial ligand. 相似文献
The equations governing the response of hysteretic systems to sinusoidal forces, which are memory dependent in the classical phase space, can be given as a vector field over a suitable phase space with increased dimension. Hence, the stationary response can be studied with the aids of classical tools of nonlinear dynamics, as for example the Poincaré map. The particular system studied in the paper, based on hysteretic Masing rules, allows the reduction of the dimension of the phase space and the implementation of efficient algorithms. The paper summarises results on one degree of freedom systems and concentrates on a two degree of freedom system as the prototype of many degree of freedom systems. This system has been chosen to be in 1:3 internal resonance situation. Depending on the energy dissipation of the elements restoring force, the response may be more or less complex. The periodic response, described by frequency response curves for various levels of excitation intensity, is highly complex. The coupling produces a strong modification of the response around the first mode resonance, whereas it is negligible around the second mode. Quasi-periodic motion starts bifurcating for sufficiently high values of the excitation intensity; windows of periodic motions are embedded in the dominion of the quasi-periodic motion, as consequence of a locking frequency phenomenon. 相似文献
The enantiospecific syntheses of both enantiomers of bacillamide C and neobacillamide A are described, along with the measurement of their optical activities, leading to the revision of the proposed absolute configurations of these natural products. 相似文献
A thermally stable carbocationic covalent organic network (CON), named RIO-70 was prepared from pararosaniline hydrochloride, an inexpensive dye, and triformylphloroglucinol in solvothermal conditions. This nanoporous organic material has shown a specific surface area of 990 m2 g−1 and pore size of 10.3 Å. The material has CO2 uptake of 2.14 mmol g−1 (0.5 bar), 2.7 mmol g−1 (1 bar), and 6.8 mmol g−1 (20 bar), the latter corresponding to 3 CO2 molecules adsorbed per pore per sheet. It is shown to be a semiconductor, with electrical conductivity (σ) of 3.17×10−7 S cm−1, which increases to 5.26×10−4 S cm−1 upon exposure to I2 vapor. DFT calculations using periodic conditions support the findings. 相似文献
We have studied using molecular dynamics simulations the interaction of the dodecaborate anion, B(12)H(12)(2-), and its amino, trimethyl, and triethyl derivatives with water molecules. We found peculiar organization of the water molecules in the first solvation shell with the formation of a dihydrogen bond between the hydrogen atoms of the anions and the hydrogen atoms of the water molecules. The simulations also show that the organization of the hydration shell is strongly influenced by the substituents in the anions. These differences are likely to play an important role in understanding the interaction of the anions with biological systems like membranes and proteins in aqueous environments. 相似文献
