Stable and Storable N(CF3)2 Transfer Reagents

Fluorinated groups are essential for drug design, agrochemicals, and materials science. The bis(trifluoromethyl)amino group is an example of a stable group that has a high potential. While the number of molecules containing perfluoroalkyl, perfluoroalkoxy, and other fluorinated groups is steadily increasing, examples with the N(CF₃)₂ group are rare. One reason is that transfer reagents are scarce and metal-based storable reagents are unknown. Herein, a set of Cu^I and Ag^I bis(trifluoromethyl)amido complexes stabilized by N- and P-donor ligands with unprecedented stability are presented. The complexes are stable solids that can even be manipulated in air for a short time. They are bis(trifluoromethyl)amination reagents as shown by nucleophilic substitution and Sandmeyer reactions. In addition to a series of benzylbis(trifluoromethyl)amines, 2-bis(trifluoromethyl)amino acetate was obtained, which, upon hydrolysis, gives the fluorinated amino acid N,N-bis(trifluoromethyl)glycine.     

Stability of AgIII towards Halides in Organosilver(III) Complexes

The involvement of silver in two-electron Ag^I/Ag^III processes is currently emerging. However, the range of stability of the required and uncommon Ag^III species is virtually unknown. Here, the stability of Ag^III towards the whole set of halide ligands in the organosilver(III) complex frame [(CF₃)₃AgX]⁻ (X=F, Cl, Br, I, At) is theoretically analyzed. The results obtained depend on a single factor: the nature of X. Even the softest and least electronegative halides (I and At) are found to form reasonably stable Ag^III−X bonds. Our estimates were confirmed by experiment. The whole series of nonradiative halide complexes [PPh₄][(CF₃)₃AgX] (X=F, Cl, Br, I) has been experimentally prepared and all its constituents have been isolated in pure form. The pseudohalides [PPh₄][(CF₃)₃AgCN] and [PPh₄][(CF₃)₃Ag(N₃)] have also been isolated, the latter being the first silver(III) azido complex. Except for the iodo compound, all the crystal and molecular structures have been established by single-crystal X-ray diffraction methods. The decomposition paths of the [(CF₃)₃AgX]⁻ entities at the unimolecular level have been examined in the gas phase by multistage mass spectrometry (MSⁿ). The experimental detection of the two series of mixed complexes [CF₃AgX]⁻ and [FAgX]⁻ arising from the corresponding parent species [(CF₃)₃AgX]⁻ demonstrate that the Ag−X bond is particularly robust. Our experimental observations are rationalized with the aid of theoretical methods. Smooth variation with the electronegativity of X is also observed in the thermolyses of bulk samples. The thermal stability in the solid state gradually decreases from X=F (145 °C, dec.) to X=I (78 °C, dec.) The experimentally established compatibility of Ag^III with the heaviest halides is of particular relevance to silver-mediated or silver-catalyzed processes.     

New Ideas for Understanding the Structure and Magnetism in AgF2: Prediction of Ferroelasticity

In the search for new high-temperature superconductors, it has been proposed that there are strong similarities between the fluoroargentate AgF₂ and the cuprate La₂CuO₄. We explored the origin of the possible layered structure of AgF₂ by studying its parent high-symmetry phase and comparing these results with those of a seemingly analogous cuprate, CuF₂. Our findings first stress the large differences between CuF₂ and AgF₂. Indeed, the parent structure of AgF₂ is found to be cubic, naturally devoid of any layering, even though Ag²⁺ ions occupy trigonal sites that, nevertheless, allow the existence of a Jahn-Teller effect. The observed Pbca orthorhombic phase is found when the system is cooperatively distorted by a local E⊗e trigonal Jahn-Teller effect around the silver sites that creates both geometrical and magnetic layering. While the distortion implies that two Ag²⁺−F⁻ bonds increase their distance by 15 % and become softer, our simulations indicate that covalent bonding and interlayer electron hopping is strong, unlike the situation in cuprate superconductors, and that, in fact, exfoliation of individual planes might be a harder task than previously suggested. As a salient feature, these results prove that the actual magnetic structure in AgF₂ is a direct consequence of vibronic contributions involved in the Jahn-Teller effect. Finally, our findings show that, due to the multiple minima intrinsic to the Jahn-Teller energy surface, the system is ferroelastic, a property that is strongly coupled to magnetism in this argentate.     

DNA/银纳米簇在分析检测中的应用

银纳米簇(AgNCs)为几个到数十个原子所组成的聚集体,核尺寸小于2 nm,具有优异的物理化学性质,常以聚合物、蛋白质、DNA等作为模板采用化学合成法制备,其中以DNA为模板合成的AgNCs(DNA/AgNCs)是一种新型的发光纳米材料,其突出的荧光特性和良好的生物相容性,被应用于纳米传感器、细胞标记与检测等多种分析领域,引起广泛关注。本文针对近些年来DNA/AgNCs在重金属离子、有机小分子、核酸、蛋白质、细胞分析检测方面的最新应用进展以及面临的问题进行简要总结概括。     

Ag@硅氧倍半聚合物的合成及其对对硝基苯酚的催化还原性能

以氨丙基三乙氧基硅烷和草酰氯为原料,合成得到链上含亚氨基和羰基官能团的硅氧倍半聚合物。以此聚合物为载体,通过配位吸附和还原得到银纳米粒子（平均粒径约为15 nm）高度分散于硅氧烷聚合物表面的复合物。研究结果表明,复合物中银负载量（质量分数）约为13.66%,在水溶液中25℃、6 min内可将对硝基苯酚（4-NP）完全催化还原为对氨基苯酚（4-AP）,且7次循环使用后依然保持95%以上的催化活性。在常温常压条件下,催化剂的最高活性达到33.0 g_4-AP·g_Ag^-1,表现出优异的催化还原性能。     

柠檬酸辅助可控制备花状银粒子及其表面增强拉曼散射性能

以抗坏血酸为还原剂,柠檬酸为结构导向剂,一步还原硝酸银,合成了尺寸和形状可调的花状银颗粒。纳米粒子的粒径可在600～1 200 nm范围内调整,表面突起可达到10～25 nm。柠檬酸的化学性质在银纳米粒子合成多级花状银结构的过程中起着至关重要的作用。通过改变柠檬酸或抗坏血酸溶液的用量,银结构的各向异性形貌可以很容易地调节。以制备的多级花状银颗粒作为表面增强拉曼散射(SERS)基底,对浓度为10~(-10)mol·L~(-1)的罗丹明6G(R6G)仍具有较高的检测灵敏度。     

AgNP-decorated SBA-15 for MWCNT Paste Modified Electrode: A Sensor for Simultaneous Voltammetric Determination of Paracetamol and Sulfamethoxazole

A new electrochemical sensor based on a carbon nanotube paste electrode modified with a Santa Barbara Amorphous material (SBA-15) decorated with silver nanoparticles, namely CNT/SBA/Ag-PE, was developed. It was successfully applied for individual and simultaneous determination of both paracetamol (PC) and sulfamethoxazole (SMZ) medicines. The electrode exhibited a linear dynamic range of 0.12–110 μmol L⁻¹ for paracetamol and 0.06–70 μmol L⁻¹ for sulfamethoxazole, and detection limits of 38 and 19 nmol L⁻¹, respectively. The proposed sensor offered high sensitivity, fast response time and the potential for detecting both drugs simultaneously. The CNT/SBA/Ag-PE enabled the simultaneous determination of PC and SMZ in urine samples with high recovery rates.     

用硝酸银溶液沉淀及分步沉淀卤素离子的数字化实验研究*

卤化银难溶电解质的沉淀溶解平衡是中学化学教学的重要知识点。应用本项目组研制的MXLab21先进数字化实验系统,结合银硫离子电极,测定AgNO₃溶液沉淀Cl^-,Br^-,I^-及其混合离子的沉淀曲线,即电动势(E)随AgNO₃溶液体积(V)变化的关系曲线。3种单一离子的沉淀曲线可以直观体现出滴定的电动势突跃范围与相应沉淀的溶度积大小的关系及其规律性变化。通过混合离子的沉淀曲线分析3种离子两两混合或3者混合时分步沉淀的可行性。Cl^-,Br^-,I^-的沉淀及分步沉淀的动态E-V曲线的建立,对中学化学教学具有重要作用,对化学学科核心素养的发展和培养具有重要价值。     

银负载量对网状TiO_2柔性薄膜电极储锂性能的影响

采用水热法结合银镜反应制备出一系列不同Ag负载量(2.2%、4.0%、6.4%,w/w)改性的3D纳米网状结构Ag@Ti O2薄膜电极。利用电感耦合等离子体技术(ICP)、X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和X射线能谱(EDX)等表征手段测试所合成材料的形貌及成分,实验结果表明Ag纳米颗粒可以成功沉积在Ti O2纳米线表面。电化学测试数据则表明,4.0%(w/w)负载量的Ag@Ti O2相比于未改性和其他负载量的Ti O2纳米线具有更好的倍率性能和更稳定的可逆容量。在50,100,200,400,800和1 200 m A·g~(-1)的电流密度条件下,该改性电极的放电容量可分别达到261.4,253.7,239.5,216.5,193.1和185.1 m Ah·g~(-1),在200 m A·g~(-1)下循环80次后容量保持率仍能达到99.8%。     

Sensitive and Selective Fluorescent and Colorimetric Sensor for Ag+ Based on the Supramolecular Self‐Assembly in Semi‐Water

Specific recognition of ultratrace levels of ions in semi‐water using super‐quicker methods is still a challenge for environmental monitoring. Herein we report a fluorescent and colormetric sensor ( ZH ) based on supramolecular self‐assembly, whose structure was destroyed by the addition of ultratrace of silver ions. The process promoted either naked eye visible color changes or fluorescence intensity quenched in conjunction with a wide pH range. Systematic studies revealed very high selectivity (0.07 µmol/L) for silver ions, and other common cations, e.g ., Hg²⁺, Cu²⁺, Cd²⁺, Pb²⁺ had nearly no influence on the sensing behavior. This sensor also served as a multiple use of component in sensing materials by addition of I⁻ into the mixture of ZH and Ag⁺ (about 5 times). What's more, ZH containing filter paper emerged distinct color and fluorescence changes upon exposure to silver (Ag⁺), which could be used as a portable method to undertake field testing for Ag ⁺ .