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101.
In this paper, the relationship between the reversible redox properties and the second-order nonlinear optical (NLO) responses for the title series of complexes has been systematically investigated by using the time-dependent density functional theory (TDDFT) method combined with the sum-over-states (SOS) formalism. The results reveal that the successive reduction processes of five PW11ReN redox states should be PW11ReVII (1) --> PW11ReVI (2) --> PW11ReV (3) --> PW11ReV1e ( 4) --> PW 11ReV2e (5). Furthermore, their electrochemical properties have been reproduced successfully. It is noteworthy that the second-order NLO behaviors can be switched by reversible redox for the present studied complexes. Full oxidation constitutes a convenient way to switch off the second-order polarizability (system 1). The incorporation of extra electrons causes significant enhancement in the second-order NLO activity, especially for the third reduced state (system 4), whose static second-order polarizability (betavec) is about 144 times larger than that of fully oxidized 1. The characteristic of the charge-transfer transition corresponding to the dominant contributions to the betavec values indicates that metal-centered redox processes influence the intramolecular donor or acceptor character. Therefore, these kinds of complexes with the facile and reversible redox states could become excellent switchable NLO materials. 相似文献
102.
Six different anionic species (fluoride, chloride, bromide, iodide, nitrate, and acetate) are tested for their abilities to form anionic adducts with neutral oligosaccharides that are detectable by MALDI-TOF mass spectrometry. Fluoride and acetate cannot form anionic adducts with the oligosaccharides in significant yields. However, bromide, iodide, and nitrate anionic adducts consistently appear in higher abundances relative to [M - H](-), just like the highly stable chloride adducts. Post-source decay (PSD) decompositions of Br(-), I(-), and NO(3)(-) adducts of oligosaccharides provide no structural information, i.e., they yield the respective anions as the main product ions. However, determination of linkage types is achieved by analysis of structurally-informative diagnostic peaks offered by negative ion PSD spectra of chloride adducts of oligosaccharides, whereas the relative peak intensities of pairs of diagnostic fragment ions allow differentiation of anomeric configurations of glycosidic bonds. Thus, simultaneous identification of the linkage types and anomeric configurations of glycosidic bonds is achieved. Our data indicate that negative ion PSD fragmentation patterns of chloride adducts of oligosaccharides are mainly determined by the linkage types. Correlation may exist between the linkage positions and fragmentation mechanisms and/or steric requirements for both cross-ring and glycosidic bond fragmentations. PSD of the chloride adducts of saccharides containing a terminal Glcalpha1-2Fru linkage also yields chlorine-containing fragment ions which appear to be specifically diagnostic for a fructose linked at the 2-position on the reducing end. This also allows differentiation from saccharides with a 1-1 linked pyranose on the same position. 相似文献
103.
Dongmei Cha Dong’e Cheng Mingming Liu Zhaorui Zeng Xiaowei Hu Wenwu Guan 《Journal of chromatography. A》2009,1216(9):1450-1457
A method based on solid-phase microextraction (SPME) and post-derivatization on the fiber coupled to gas chromatography–mass spectrometry (GC–MS) was developed for the analysis of fatty acids in sputum from patients with pulmonary tuberculosis. The sputum specimens were digested, hydrolyzed, extracted, derivertized, injected and analyzed without cultivation or isolation of the microorganism. Under optimized conditions, the relative standard deviations (RSD, n = 5) for all analytes were below 17% and the limits of detection varied from 1.68 (C24:0) to 150.4 μg L−1 (C12:0). Good linearity was observed for all the fatty acids studied except for C12:0 within a wide concentration range of three orders of magnitudes with the correlation coefficients ranging from 0.91 (C24:0) to 0.99 (C14:0). Fatty acids in sputum specimens from 21 persons were directly analyzed using the proposed method. The results show that in all the sputum specimens from patients, who were clinically diagnosed with tuberculosis (TB), tuberculosis stearic acid (TBSA) was detected, while in all the sputum samples from persons without TB, TBSA was not found. The possibility of using the proposed method to detect mycobacterium tuberculosis (MTB) via the identification of TBSA in sputum was discussed. The comparison with other methods including sputum culture and microscopy of direct smears indicated that the proposed method is fast and sensitive for the analysis of fatty acids in sputum and offers an alternative for the detection of MTB in sputum. 相似文献
104.
Liang Li Chang‐Yun Wang Chang‐Lun Shao Yue‐Wei Guo Guo‐Qiang Li Xue‐Ping Sun Lei Han Hui Huang Hua‐Shi Guan 《Helvetica chimica acta》2009,92(8):1495-1502
Chemical examination of the soft coral Sarcophyton infundibuliforme collected from the South China Sea resulted in the isolation of the three new O‐glycosylglycerol derivatives sarcoglycosides A–C ( 1 – 3 ), together with two known compounds, chimyl alcohol ( 4 ) and hexadecanol ( 5 ). Their structures were elucidated by combined spectral and chemical methods. All the compounds showed moderate toxicity to brine shrimps Artemia salina. 相似文献
105.
Zhongzheng Yu Wenbo Hu Hui Zhao Xiaofei Miao Yan Guan Weizheng Cai Zhiping Zeng Quli Fan Timothy Thatt Yang Tan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(25):8624-8628
Cross‐relaxation among sensitizers is commonly regarded as deleterious in fluorescent materials, although favorable in photothermal agents. Herein, we coated Prussian blue (PB) on NaNdF4 nanoparticles to fabricate core–shell nanocomplexes with new cross relaxation pathways between the ladder‐like energy levels of Nd3+ ions and continuous energy band of PB. The photothermal conversion efficiency was improved exceptionally and the mechanism of the enhanced photothermal effect was investigated. In vivo photoacoustic imaging and photothermal therapy demonstrated the potential of the enhanced photothermal agents. Moreover, the concept of generating new cross‐relaxation pathways between different materials is proposed to contribute to the design of all kinds of enhanced photothermal agents. 相似文献
106.
Jianyou Mao Zhiting Wang Xinyu Xu Guoqing Liu Runsheng Jiang Haixing Guan Zhipeng Zheng Patrick J. Walsh 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(32):11149-11154
Indoles are essential heterocycles in medicinal chemistry, and therefore, novel and efficient approaches to their synthesis are in high demand. Among indoles, 2‐aryl indoles have been described as privileged scaffolds. Advanced herein is a straightforward, practical, and transition‐metal‐free assembly of 2‐aryl indoles. Simply combining readily available 2‐fluorotoluenes, nitriles, LiN(SiMe3)2, and CsF enables the generation of a diverse array of indoles (38 examples, 48–92 % yield). A range of substituents can be introduced into each position of the indole backbone (C4 to C7, and aryl groups at C2), providing handles for further elaboration. 相似文献
107.
建立了基质固相分散萃取-高效液相色谱-串联质谱法(MSPD-HPLC-MS/MS)同时测定拟南芥中3种赤霉素GA1, GA3和GA4的分析方法。将拟南芥样品与C18填料混合研磨制成MSPD柱,并采用80%冷甲醇洗脱。采用反相C18色谱柱进行分离,以0.05%甲酸水溶液和乙腈为流动相进行梯度洗脱,采用电喷雾离子源负离子模式(ESI~)电离,多反应监测模式检测。对样品前处理条件、色谱分离条件和质谱检测条件进行了优化,结果表明,在最优条件下,3种赤霉素在10~300 ng/g范围内均呈良好线性关系,相关系数(r2)均大于0.98,检出限在1.1~4.1 ng/g之间。在10~50 ng/g添加水平下,平均回收率范围为54.7%~102.6%,相对标准偏差(RSD,n=3)为3.2%~12.8%。该方法操作简单、灵敏度高、选择性好、回收率高,适合拟南芥中GA1、GA3、GA4含量的测定。 相似文献
108.
109.
H. X. Ma B. Yan Y. H. Ren Y. Hu Y. L. Guan F. Q. Zhao J. R. Song R. Z. Hu 《Journal of Thermal Analysis and Calorimetry》2011,103(2):569-575
3,3-Dinitroazetidinium (DNAZ) salt of perchloric acid (DNAZ·HClO4) was prepared, it was characterized by the elemental analysis, IR, NMR, and a X-ray diffractometer. The thermal behavior
and decomposition reaction kinetics of DNAZ·HClO4 were investigated under a non-isothermal condition by DSC and TG/DTG techniques. The results show that the thermal decomposition
process of DNAZ·HClO4 has two mass loss stages. The kinetic model function in differential form, the value of apparent activation energy (E
a) and pre-exponential factor (A) of the exothermic decomposition reaction of DNAZ·HClO4 are f(α) = (1 − α)−1/2, 156.47 kJ mol−1, and 1015.12 s−1, respectively. The critical temperature of thermal explosion is 188.5 °C. The values of ΔS
≠, ΔH
≠, and ΔG
≠of this reaction are 42.26 J mol−1 K−1, 154.44 kJ mol−1, and 135.42 kJ mol−1, respectively. The specific heat capacity of DNAZ·HClO4 was determined with a continuous C
p mode of microcalorimeter. Using the relationship between C
p and T and the thermal decomposition parameters, the time of the thermal decomposition from initiation to thermal explosion (adiabatic
time-to-explosion) was evaluated as 14.2 s. 相似文献
110.
Comparison and characterization of polysaccharides from natural and cultured Cordyceps on the basis of their chemical characteristics such as glycosidic linkages were performed for the first time using saccharide
mapping. The results showed that polysaccharides from most of the natural and cultured Cordyceps had similar responses to enzymatic digestion. These polysaccharides mainly contained (1→4)-β-D-glucosidic linkages, and (1→4)-α-glucosidic, (1→6)-α-glucosidic, 1,4-β-D-mannosidic, as well as (1→4)-α-D-galactosiduronic linkages also existed in some polysaccharides. Especially, natural and cultured Cordyceps polysaccharides could be discriminated on the basis of high performance liquid chromatography profiles of pectinase hydrolysates,
which is helpful to control the quality of polysaccharides from Cordyceps. 相似文献