The photochemistry of some members of the two series of γ-phenyl substituted acyclic β, γ-unsaturated ketones 1 and 2 upon direct irradiation with γ 310nm has been investigated, viz 1c–1h and 2b+2c.The alkyl substituted (E)-5-phenyl-4-penten-2-ones 1c–1h yield the corresponding 1,3-acyl shift products and (Z)-isomers, and 1g and 1h in addition two decarbonylated products. 2b only yields the (Z)-isomer and some benzaldehyde, but 2c yields the 1,3-acyl shift product, the ODPM product, three hydrocarbons formed by disproportionation of the allyl radical, and some benzaldehyde. The β-phenyl β, γ-UK 3a proved to be photostable. The 1,3-acyl shift products of 1c–1h result mainly from the singlet excited state in a cage radical process. The exclusive formation of the (E)-configuration of the 1,3-acyl shift product is explained in terms of conformational preference of the intermediate allyl radical. It is proposed that the formation of the (Z)-isomer proceeds from 1T(π -π*) which is populated according to . Evidence is presented which supports the proposed mechanism.The β,γ-UK 2b containing a benzoyl moiety leads to a higher degree of (E)-(Z) isomerization than the corresponding 1d which has an acetyl moiety.The triplet energies of (E)- and (Z)-1h are 56 and ca 70 kcal/mol respectively. 相似文献
Zeolite synthesis in contemporary chemical industries is predominantly conducted using organic structure-directing agents (OSDAs), which are chronically hazardous to humans and the environment. It is a growing trend to develop an eco-friendly and nuisanceless OSDA for zeolite synthesis. Herein, choline is employed as a non-toxic and green OSDA to synthesize high silica Y zeolite with SiO2/Al2O3 ratios of 6.5–6.8. The prepared Y zeolite samples exhibited outstanding (hydro)thermal stability at ultrahigh temperature owing to the higher SiO2/Al2O3 ratio. The XRF, SEM, 29Si-NMR and 13Na+ results suggested that choline plays a structure-directing role in the synthesis of Y zeolite, while the feed molar fraction of Na+ is a crucial determinant for the framework SiO2/Al2O3 ratio and the crystal morphology. 相似文献
iPP/sPP, iPP/rPP, iPP/PVDF and iPP/PA-6 blends, and their β-nucleated forms were prepared in the present study. The components of iPP/sPP and iPP/rPP blends are compatible in the molten state. The phase structure of the melt of iPP/PVDF and iPP/PA-6 blends is heterogeneous. The melting and crystallisation characteristics as well as the structure and polymorphic composition of these blends were studied by polarised light microscopy (PLM) and differential scanning calorimetry (DSC). When semicrystalline polymers are added to iPP, the most important factor of the formation a blend with β-crystalline phase is the α-nucleation effect of the second polymer. In the case of polymers with an α-nucleating effect, the temperature range of their crystallisation should be lower than that of β-iPP. β-nucleated iPP/PVDF and iPP/PA-6 blends are extreme examples showing that completely β-iPP matrix can not form even in the presence of a highly effective β-nucleant, because of the strong α-nucleating ability and higher crystallisation temperature range of PVDF and PA-6. We found that the β-crystallisation tendency of random propylene copolymers can be enhanced by adding an iPP homopolymer. 相似文献
Charge transfer via electron hopping from an electron donor (D) to an acceptor (A) in nanoscale, plays a crucial role in optoelectronic materials, such as organic light-emitting diodes (OLEDs) and organic photovoltaic cells (OPVs). Here, we propose a strategy for binding D/A units in space, where intramolecular charge-transfer can take place. The resulted material DM-Me-B is able to give bright emission in this molecular architecture because of the good control of D/A interaction and conformational rigidity. Moreover, DM-Me-B presents small singlet-triplet splitting energy, enabling thermally activated delayed fluorescence. Therefore, the DM-Me-B exhibits ~20% maximum external quantum efficiency and low efficiency roll-off at 1000 cd/m2, certifying an effective strategy in controlling D/A blocks through space. 相似文献
The preconcentration technique of purge-and-trap has been investigated in the present work for quantitative adsorption of volatile organic pollutants purged from water samples. A dynamic purging device with variable volume size has been constructed and tested to purge different concentrations of organic compounds. With Tenax GR as the adsorbent, a dynamic purge-and-trap technique was developed combining on-column preconcentration procedures using ambient trapping/thermal desorption/cryogenic focusing/back-flash injection prior to separation and determination using capillary gas chromatography. Various aromatic compounds in water were determined, giving linear working ranges over five orders of magnitude from 0.02 to 5000 µg/L. The analytical procedures were optimized under the assistance of ultrasonication with results validated for the determination of organic contaminants in underground water and tap water, giving over 93% recoveries and a detection limit of 0.01 µg/L, two orders of magnitude lower than those obtained using commercial available instruments with on-line configuration to minimize cross-contamination. The technique provides a potential automated method for in situ monitoring of volatile organic compounds in water. 相似文献
A novel methodology was implemented in the present study to concurrently control power conversion efficiency (η) and durability (D) of co-sensitized dye solar cells. Applying response surface methodology (RSM) and Desirability Function (DF), the main influential assembling (dye volume ratio and anti-aggregation agent concentration) and operational (performance temperature) parameters were systematically changed to probe their main and interactive effects on the η and D responses. Individual optimization based on RSM elucidated that D can be solely controlled by changing the ratio of vat-based organic photosensitizers, whereas η takes both effects of dye volume ratio and anti-aggregation concentration into account. Among the studied factors, the performance temperature played the most vital role in η and D regulation. In particular, however, multi-objective optimization by DF explored the degree to which one should be careful about manipulation of assembling and operational parameters in the way maximization of performance of a co-sensitized dye solar cell. 相似文献
This study was to describe the synthesis of complexes of gadolinium diethylenetriaminepentaacetic acid conjugates of low-molecular-weight chitosan oligosaccharide Gd-DTPA-CSn (n = 6, 8, 11) as a new class of contrast agent as well as its magnetic property in a pilot magnetic resonance imaging. The efficacy of the contrast agent was assessed by measuring the longitudinal relaxivity (r1), FLASH imaging in phantoms in vitro and signal intensity in vivo of the rat abdominal axial imaging. The r1 of Gd-DTPA-CS11 was up to 11.65 mM− 1·s− 1, which was 3 times higher than that of the analogous MRI contrast agent Gd-DTPA in commercial use. In vivo MR images of rat obtained with Gd-DTPA-CS11 showed strong signal enhancement in liver and the vessels of the liver parenchyma during the extended period of time. The present study suggests that the new synthesized gadolinium complexes can be used as a new class of practical liver-specific MRI contrast agent because of its superior performance compared with Gd-DTPA. 相似文献
A cyclotriphosphazene substituted with six 3,5-bis(trifluoromethyl) benzyloxy units was designed as a novel 19F MRI contrast agent. The resulting molecule has 36 magnetically equivalent fluorine atoms and exhibited suitable MRI properties with high imaging sensitivity, confirming the proof-of-concept as a convenient scaffold for the production of new 19F MRI contrasts agents. 相似文献