CL-20 photodecomposition: ab initio foundations for identification of products

1,5-Dihydrodiimidazo[4,5-b:4'5'e]pyrazine, 1H-imidazo[4,5-b]pyrazine, and 1H-imidazole were considered as possible products of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) photodecomposition. Since we took as a reference the product obtained after CL-20 irradiation in methanol solution, the nature of intermolecular bonds between heterocycles under study and methanol molecules was analyzed in detail. Existing hydrogen bonds were found to be quite strong, so dependence of calculations results on an influence of solvent was taken into account using both the polarizable continuum model (PCM) and the supermolecular approach. Electronic spectra of 1,5-dihydrodiimidazo[4,5-b:4'5'e]pyrazine, 1H-imidazo[4,5-b]pyrazine and 1H-imidazole were simulated using time dependent density functional theory (TD-DFT) and single-excitation configuration interaction (CIS) method. We observed that TD-DFT excitation energies are lower if compared to corresponding values obtained by the CIS method. Results of calculations with PCM and the supermolecular approach are very close. It was found that differences between calculated gas phase excitation energies and those values obtained by applying solvent models increases when the number of conjugated bonds in a molecule increases. Oscillator strengths of UV bands of the considered molecules are higher in the gas phase than in modeled methanol solutions. We found that the predicted spectrum of 1H-imidazole is in close agreement with the experimental UV spectrum of the CL-20 photolysis product.     

Photocatalytic decomposition of dinitrogen monoxide on zinc-supporting porous Vycor glass

Zinc-supporting (0.05–0.61 wt.%) porous Vycor glass was found to act as a photocatalyst for the decomposition of dinitrogen monoxide at 278 K. The active species of zinc ion coordinated by oxygen ion is suggested.     

六硝基菧的紫外光解

采用紫外-可见光谱、X-射线光电子能谱、电子自旋共振谱及质谱等实验手段研究了固态含能材料六硝基菧（HNS）在365 nm紫外光照下的光解机理。HNS的乙腈溶液被紫外光照射后,在310 nm和350 nm处出现了两个新的吸收峰。X-射线光电子能谱实验中,N元素和O元素的窄谱图分别在401 eV和528 eV处出现了新峰。质谱分析则显示在质荷比403和329处出现了两个新的特征离子峰。实验结果表明：CNO2键断裂、分子中NO2基团异构化为亚硝基,以及随后的NO消去等过程均可能发生在六硝基菧的紫外光解反应过程中。     

一种微光刻全息记录新材料：光刻蚀纤维素软片成像机理及其特性研究

报道一种新型的聚合物全息记录材料：光刻蚀纤维素软片（ＰＣＦ），对该材料较强的实时特性、较高的分辨本领、线性的表面浮雕调制特性等进行了实验研究，同时通过电子自旋共振谱（ＥＳＲ）、红外谱（ＩＲ）等手段研究了其成像过程中的光化学反应过程，证实了它的光降解机理。     

MOF Decomposition and Introduction of Repairable Defects Using a Photodegradable Strut

Photoswitchable components can modulate the properties of metal organic frameworks (MOFs); however, photolabile building blocks remain underexplored. A new strut NPDAC (2-nitro-1,4-phenylenediacetic acid) that undergoes photodecarboxylation has been prepared and incorporated into a MOF, using post-synthetic linker exchange (PSLE) from the structural analogue containing PDAC (p-phenylenediacetic acid). Irradiation of NPDAC-MOF leads to MOF decomposition and concomitant formation of amorphous material. In addition to complete linker exchange, MOFs containing a mixture of PDAC and NPDAC can be obtained through partial linker exchange. In NPDAC30-MOF, which contains approximately 30 % NPDAC, the MOF retains crystallinity after irradiation, but the MOF contains defect sites consistent with loss of decarboxylated NPDAC linkers. The defect sites can be repaired by exposure to additional PDAC or NPDAC linkers at a much faster rate than the initial exchange process. The photoremoval and replacement process may lead to a more general approach to customizable MOF structures.     

Redox reactions of natural alkaloid lappaconitine

A review on redox reactions of natural alkaloid lappaconitine, a known sodium channel blocker, is presented. The NMR and CIDNP data on the mechanism of phototransformation of lappaconitine, in particular, of its paramagnetic species formed by both the direct photolysis and photoinitiated interaction with electron donors and acceptors, are analyzed. Special attention is given to the interaction of lappaconitine with amino acids, which are present in the active site of the sodium channel. Hypotheses about a relationship between this process and the mechanism of therapeutic activity of lappaconitine are discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 608–619, April, 2007.     

Silver nanoclusters doped in X and mordenite zeolites as heterogeneous catalysts for the decomposition of carbamate pesticides in solution

Ag(I) nanoclusters doped in X and mordenite zeolites were prepared and analyzed using spectroscopy. Both experimental and theoretical studies of the prepared compounds show the presence of silver nanoclusters with various sizes and environments. The presence of Ag(I) nanoclusters doped in X and mordenite zeolites with high silver loadings enhanced the photodecomposition rate of carbofuran 215-and 184-fold, respectively, while the photodecomposition of carbaryl in the presence of these catalysts show room temperature rate constants that are 182-and 168-times faster than the photodecomposition of carbaryl in the absence of the silver-doped zeolite catalysts. The reaction rates were found to be dependent on the amount of silver loaded into the zeolite.     

不同紫精在光解水释氢反应中的影响

本文研究了以非水溶性的四苯基卟啉锌为敏化剂,各种不同紫精化合物为电子中继物,胶体铂为催化剂,乙二胺四乙酸二钠盐为电子给体组成的四组分胶束体系的光分解水释氢反应。着重讨论了这些紫精化合物对该反应的影响。     

The Photochemistry of Carbamates,I

Abstract

The photodecomposition of 4-dimethylamino-3,5-xylyl-N-methyl carbamate (Zectran) in aerated and degassed solution has been carried out. Three major photoproducts were detected and characterized to be: 4-dirnethylamino-3,5-dimethyl Rhenol, 4-hydroxy-2,6-dimethyl-N-methyl benzamide and 4-monomethylamino-3,5-xylyl-N-methyl carbamate. The phenol and benzamide products suggest that one of the pathways of photodecomposition of Zectran is via a photo-Fries rearrangement. The ortho-benzamide (5-dimethylamino-4,6-dimethyl-2-hydroxy-N-methyl benzamide) which could also be expected to occur in a photo-Fries reaction, was not observed. The excitation wavelength was > 296.7 nm, i.e. radiation available in the solar spectrum. Thus the products observed in this study may be expected to occur in the environment as a result of the action of sunlight on Zectran.     

Formation and decay of trifluoromethyl radicals during photodecomposition of the long-lived perfluoro-2,4-dimethyl-3-ethylpent-3-yl radical

UV irradiation of the long-lived radical [(CF₃)₂CF]₂C^·C₂F₅ (1) in a hexafluoropropylene trimer (HFPT) glassy matrix at 77 K and in a HFPT solution at 300 K leads to its decomposition to the ^·CF₃ radical and perfluoroolefin molecule. About 90% of the ^·CF₃ radicals formed recombine at 300 K. The remaining radicals add to the HFPT molecules generating the long-lived radicals [(CF₃)₂CF]₃C^·. Unlike the ^·CF₃ radicals produced by the photodecomposition of radicals 1, the ^·CF₃ radicals formed during radiolysis of HFPT are not stabilized in the glassy HFPT matrix at 77 K.