Improvements on the optical properties of Ge-Sb-Se chalcogenide glasses with iodine incorporation

International audienceDecreasing glass network defects and improving optical transmittance are essential work for material researchers. We studied the function of halogen iodine (I) acting as a glass network modifier in Ge–Sb–Se–based chalcogenide glass system. A systematic series of Ge20Sb5Se75-xIx (x = 0, 5, 10, 15, 20 at%) infrared (IR) chalcohalide glasses were investigated to decrease the weak absorption tail (WAT) and improve the mid-IR transparency. The mechanisms of the halogen I affecting the physical, thermal, and optical properties of Se-based chalcogenide glasses were reported. The structural evolutions of these glasses were also revealed by Raman spectroscopy and camera imaging. The progressive substitution of I for Se increased the optical bandgap. The WAT and scatting loss significantly decreased corresponding to the progressive decrease in structural defects caused by dangling bands and structure defects in the original Ge20Sb5Se75 glass. The achieved maximum IR transparency of Ge–Sb–Se–I glasses can reach up to 80% with an effective transmission window between 0.94 μm to 17 μm, whereas the absorption coefficient decreased to 0.029 cm-1 at 10.16 μm. Thus, these materials are promising candidates for developing low-loss IR fibers

Fabrication and characterization of Ge–Sb–Se–I glasses and fibers

International audienceChalcogenide glasses of the Ge20Sb5Se75−x I x (x = 0, 5, 10, 15, 20 at.%) system were prepared. This study was performed to examine some Ge–Sb–Se–I glass physical and optical properties, the structural evolution of the glass network, and the optical properties of the infrared glass fibers based on our previous studies. The variation process of the glass physical properties, such as transition temperature, glass density, and refractive index, was investigated from the glass of Ge20Sb5Se75 to the Ge20Sb5Se75−x I x glass series. The structural evolutions of these glasses were examined by Raman spectroscopy. The Ge20Sb5Se55I20 composition was selected for the preparation of the IR fiber. The Ge20Sb5Se55I20 glass was purified through distillation, and the intensity of the impurity absorption peaks caused by Ge–O, H2O, and Se–H was reduced or eliminated in the purified glasses. Then, Ge20Sb5Se55I20 chalcogenide glass fiber for mid-infrared transmission was fabricated using high-purity materials. The transmission loss of the Ge20Sb5Se55I20 fiber was greatly reduced compared with that of the Ge20Sb5Se75 glass fiber. The lowest losses obtained were 3.5 dB/m at 3.3 μm for Ge20Sb5Se75I20 fiber, which was remarkably improved compared with 48 dB/m of the unpurified Ge20Sb5Se75 fiber

Constraint of a ruthenium-carbon triple bond to a five-membered ring

含过渡金属碳三键(M≡C)的金属卡拜化合物是许多有机反应的催化剂或关键中间体。对其合成及性质的研究是金属有机化学的热点之一。由于卡拜碳的sp杂化方式，大部分金属卡拜化合物均为链状结构（卡拜碳键角理想值为180 °），环内金属卡拜化合物因存在很大的环张力而难于合成。夏海平教授课题组发展了由链状多炔（称之为碳龙）构筑碳龙配合物的高效方法（Nature Communications, 2017, 8, 1912），实现了锇杂戊搭炔/烯及其衍生物的一锅法合成。现在，他们把该方法进一步拓展到了第二过渡系金属钌，通过碳龙与市售的RuCl2(PPh3)3反应一锅合成了钌杂戊搭炔I。本研究是碳龙化学的进一步延伸和发展，首次把碳龙化学的金属中心由锇拓展到了其它金属，展示了碳龙化学广阔的发展空间。该研究工作在夏海平教授指导下完成，能源材料化学协同创新中心（iChEM）博士后卓庆德和张弘副教授为共同第一作者。iChEM博士后周小茜、博士生陈志昕、林剑锋、卓凯玥、硕士康慧君、林鑫磊参与了部分实验工作。博士生华煜晖负责理论计算。【Abstract】The incorporation of a metal-carbon triple bond into a ring system is challenging because of the linear nature of triple bonds. To date, the synthesis of these complexes has been limited to those containing third-row transition metal centers, namely, osmium and rhenium. We report the synthesis and full characterization of the first cyclic metal carbyne complex with a second-row transition metal center, ruthenapentalyne. It shows a bond angle of 130.2(3)° around the sp-hybridized carbyne carbon, which represents the recorded smallest angle of second-row transition metal carbyne complexes, as it deviates nearly 50° from the original angle (180°). Density functional theory calculations suggest that the inherent aromatic nature of these metallacycles with bent Ru≡C–C moieties enhances their stability. Reactivity studies showed striking observations, such as ambiphilic reactivity, a metal-carbon triple bond shift, and a [2 + 2] cycloaddition reaction with alkyne and cascade cyclization reactions with ambident nucleophiles.This research was supported by the National Key R&D Program of China (2017YFA0204902) and the National Natural Science Foundation of China (nos. 21490573,21332002, and 21561162001). 研究工作得到国家自然科学基金项目（21490573、21332002 和21561162001）和国家重点研发计划（2017YFA0204902）的资助

Reactions of Osmium Hydrido Alkenylcarbyne with Allenoates: Insertion and [3+2] Annulation

通讯作者地址: Zhang, HTreatment of the osmium hydrido alkenylcarbyne complex [OsH{equivalent to CC(PPh3)=CHPh}(PPh3)(2)Cl-2]BF4 (1) with allenoates (CH2=C=CHCOOR, R = Me, Et) in the presence of excess AgBF4 leads to the insertion products 2/3. The reactions of complex 1 with substituted allenoates, i.e., diethyl 2-vinylidenesuccinate (CH2=C=C(CH2COOEt)(COOEt)) and ethyl penta-2,3-dienoate (CH(CH3)=C=CH(COOEt)), result in the formation of [3 + 2] annulation products 4 and 6, respectively. Mechanisms of the reactions have been proposed with the isolation of the key intermediates. The results reveal that the divergent pathways for these reactions are mainly of steric origin.National Natural Science Foundation of China 21272193 21332002 21490573 program for Changjiang Scholars and Innovative Research Team in Universit

Successive modification of polydentate complexes gives access to planar carbon-and nitrogen-based ligands

以碳和氮为键合原子的多齿螯合物是配合物家族中非常重要的一类。具有更高齿数的平面构型NC螯合物实例相对较少，代表性的例子为四齿金属碳卟啉类化合物，这类螯合物以其独特的结构和丰富的物理化学性质引起广泛关注。然而平面五齿、六齿的NC螯合物由于几何构型“拥挤”导致合成难度高，该工作从含三元环内金属卡宾结构的CCCC型碳龙配合物出发，利用经典有机反应（炔烃对金属卡宾的插入反应），成功地实现了CCCCN/NCCCN型平面五齿螯合物的合成。这一研究为高配位型螯合物的合成提供了新思路并为平面五齿螯合物家族添加新成员。特别是，这些高配位型螯合物在可见光和近红外区域均有较好的吸收，表现出良好的光声成像、光热转换及声动力学性能。 该研究工作在张弘教授指导下完成，第一作者为iChEM博士后周小茜。该工作充分体现了多学科协同研究优势：相关化合物的合成、表征及理论计算工作由周小茜博士完成；声动力学性能研究由厦门大学公共卫生学院庞鑫博士及刘刚教授完成；光声成像研究由厦门大学公共卫生学院聂立铭教授完成。iChEM fellow卓庆德博士、博士生卓凯玥、陈志昕参与了部分实验工作。夏海平教授、香港科技大学林振阳教授和南京大学朱从青教授对研究工作给予了大力支持。【Abstract】Polydentate complexes containing combinations of nitrogen and carbon (N and C) ligating atoms are among the most fundamental and ubiquitous molecules in coordination chemistry, yet the formation of such complexes with planar high-coordinate N/C sites remains challenging. Herein, we demonstrate an efficient route to access related complexes with tetradentate CCCN and pentadentate CCCCN and NCCCN cores by successive modification of the coordinating atoms in complexes with a CCCC core. Combined experimental and computational studies reveal that the rich reactivity of metal-carbon bonds and the inherent aromaticity of the metallacyclic skeletons play key roles in these transformations. This strategy addresses the paucity of synthetic approaches to mixed N/C planar pentadentate chelating species and provides valuable insights into the synthesis of carbon-based high-coordinate complexes. Furthermore, the resulting complexes are the examples of organometallic species with combined photoacoustic, photothermal, and sonodynamic properties, which makes them promising for application in related areas.This research was supported by the National Natural Science Foundation of China (Nos. 21572185, 21561162001, and 81571744), the Research Grants Council of Hong Kong (N_HKUST603/15), the Excellent Youth Foundation of Fujian Scientific Committee (2018J06024), and the Fundamental Research Funds for the Central Universities (20720170065).该工作得到国家自然科学基金委、香港研究资助局、福建省自然科学基金、厦门大学校长基金的资助

Laxative effects of partially defatted flaxseed meal on normal and experimental constipated mice

<p>Abstract</p> <p>Background</p> <p>Constipation is a very common health problem in the world. Intake of sufficient amount of dietary fibers is a cornerstone in the prevention and treatment of constipation. As a traditional medicine, flaxseed has been used to treat constipation for centuries, but the controlled trials are rare. The purpose of the present study was to assess that whether partially defatted flaxseed meal (PDFM) has the potential role to facilitate fecal output in normal and experimental constipated mice.</p> <p>Methods</p> <p>After supplemented with 2.5%, 5% and 10% (w/w) PDFM (L-, M- and H -PDFM) for 14 days, the constipation models of mice were induced by atropine-diphenoxylate. The small intestinal transit rates, start time of defecation, amount of defecation and wet weight of feces were researched in normal and constipation model mice.</p> <p>Results</p> <p>M- and H-PDFM significantly increase small intestinal transit rates in constipation model mice. All dose of PDFM markedly shortened the start time of defecation and M- and H-PDFM significantly increase stool frequency and weight in both normal and constipation model mice.</p> <p>Conclusions</p> <p>PDFM may be a useful laxative to facilitate fecal output in normal and constipation conditions.</p