2D Poly(arylene vinylene) Covalent Organic Frameworks via Aldol Condensation of Trimethyltriazine

Designing structural order in electronically active organic solids remains a great challenge in the field of materials chemistry. Now, 2D poly(arylene vinylene)s prepared as highly crystalline covalent organic frameworks (COFs) by base‐catalyzed aldol condensation of trimethyltriazine with aromatic dialdehydes are reported. The synthesized polymers are highly emissive (quantum yield of up to 50 %), as commonly observed in their 1D analogues poly(phenylene vinylene)s. The inherent well‐defined porosity (surface area ca. 1000 m² g^?1, pore diameter ca. 11 Å for the terephthaldehyde derived COF‐1) and 2D structure of these COFs also present a new set of properties and are likely responsible for the emission color, which is sensitive to the environment. COF‐1 is highly hydrophilic and reveals a dramatic macroscopic structural reorganization that has not been previously observed in framework materials.     

Stable Tetra‐ and Penta‐Anions in the Gas Phase

The quest for stable gas‐phase anions in highly negative charge states has been a great challenge. While multiply charged anions are stabilized in solids and liquids by compensating cations and solvation cells, respectively, stable anions containing less than a hundred atoms in the gas phase and capable of carrying charge beyond ?3 is unknown. Here, we report the discovery of thermodynamically stable tetra‐ and penta‐anions, containing less than 50 and 80 atoms, respectively, in the gas phase. A universal model is developed that explains their stability in terms of the synergy between closed shell, high electron affinity, and size and predicts new highly‐charged anions by using the known charged clusters as building blocks. Synthesis of these species can open a new chapter in materials chemistry.     

Estimation of Physico-chemical Properties of Ionic Liquid EPReO_4 Using Surface Tension and Density

An ionic liquid (IL) EPReO₄ (N‐ethylpyridinium rheniumate) was prepared. The density and surface tension values of the IL were determined in the temperature range of 293.15–343.15 K. The ionic volume and surface entropy of the IL were estimated by extrapolation, respectively. In terms of Glasser's theory, the standard molar entropy and lattice energy of the IL were estimated, respectively. Using Kabo's and Rebelo's methods, the molar enthalpy values of vaporization of the IL, Δ^g_lH⁰_m (298 K), at 298 K and, Δ^g_lH⁰_m (T_b), at hypothetical normal boiling point were estimated, respectively. According to the interstice model, the thermal expansion coefficient of IL EPReO₄ (α) was calculated and compared with experimental value, finding their magnitude order is in good agreement by 8.98%.     

Excited State Intramolecular Proton Transfer of New Diphenylethylene Derivatives Bearing Imino Group: A Combination of Experimental and Theoretical Investigation

In this paper, we described the synthesis and characterization of new diphenylethylene bearing imino group. We concentrated particularly on the investigation of the possibility of the excited state intramolecular charge transfer (ESIPT) of the new dyes experimentally and theoretically. The absorption and fluorescence spectroscopy of the dyes were determined in various solvents. The results showed that the maximal absorption wavelength of 2‐[(4′‐N,N‐dimethylamino‐diphenylethylene‐4‐ylimino)methyl]phenol ( C1 ) and 4‐[(4′‐N,N‐dimethylamino‐diphenylethylene‐4‐ylimino)methyl]phenol ( C2 ) exhibited almost independence on the solvent polarity. While as contrast, the maximal fluorescence wavelength of the dyes showed somewhat dependence on the solvent polarity. In particular, C1 displayed well‐separated dual fluorescence spectroscopy. The second fluorescence peak was characterized with an "abnormal" fluorescence emission wavelength in aprotic solvents with large Stokes shift (ca. 140 nm in THF), which was much more than normal Stokes shift (ca. 30 nm in THF). This emission spectroscopy could be assigned to ESIPT emission. On the other hand, the ESIPT fluorescence of C1 was much reduced or lost in the protic solvents. While, only normal fluorescence emission was detected in various solvents. Although the absorption maxima of C1 exhibited about 10 nm red‐shift with respect to those of C2 , the normal fluorescence maxima of C1 and C2 were almost identical in various solvents. These results suggested that C1 could undergo ESIPT, but C2 was not able to proceed ESIPT. The molecular geometry optimization of phototautomers in the ground electronic state (S₀) was carried out with HF method (Hartree‐Fock) and at DFT level (Density Functional Theory) using B3LYP both, while the CIS was employed to optimize the geometries of the first singlet excited state (S₁) of the phototautomers of C1 and C2 respectively. The properties of the ground state and the excited state of the phototautomers of C1 and C2 , including the geometrical parameter, the energy, the frontier orbits, the Mulliken charge and the dipole moment change were performed and compared completely. The data were analyzed further based on our experimental results. Furthermore, the absorption and fluorescence spectra were calculated in theory and compared with the measured ones. The rate constant of internal proton transfer (9.831×10¹¹ s^?1) of C1 was much lower than that of salicylidene methylamine ( C3 , 2.045×10¹⁵ s^?1), which was a typical Schiff base compound and was well demonstrated to undergo ESIPT easily under photoexcitation.     

固相萃取气相色谱-质谱法测定蔬菜中含氮杂环农药残留

建立了固相萃取（SPE）气相色谱-质谱（GC-MS）同时测定蔬菜中敌菌灵、噻菌灵、氟虫腈和噻嗪酮4种含氮杂环农药残留量的分析方法.蔬菜样品用乙腈匀浆提取后经弗罗里硅（Florisil）固相萃取柱净化.采用GC-MS检测,在选择离子检测（SIM）模式下以特征离子定量,用全扫描（SCAN）方法确证.方法具有良好的线性关系（R≥0.9953）和重现性（峰面积RSD≤9.1%）,最低检出限（S/N=3）在3.6~1.8×10-4μg/mL之间,4种农药添加回收率在76.1%~116.4%之间,RSD≤9.8%,用于实际样品菜心的检测,结果满意.方法操作简单,灵敏度高,可作为测定各种蔬菜基质中含氮杂环农药残留量的确证方法.     

禽蛋中头孢噻肟残留的高效液相色谱-串联质谱法测定

建立了高效液相色谱-串联质谱(LC-MS/MS)测定禽蛋中头孢噻肟药物残留的方法。禽蛋样品中的头孢噻肟用纯水提取,乙腈沉淀蛋白,Oasis HLB(500 mg,6 mL)固相萃取柱净化,8 mL甲醇洗脱。采用Zorbax XDB-C18(2.1 mm×50 mm,3.5μm)色谱柱,以0.2%甲酸水-乙腈为流动相,0.3 mL/min梯度洗脱,经高效液相色谱分离后,采用电喷雾质谱正离子模式电离,多反应选择离子检测(MRM)模式测定。检测离子对为m/z456.1/396.1、m/z456.1/324.1,其中m/z456.1/396.1为定量离子对。在1.35~135μg/L范围内标准曲线的线性关系良好,相关系数为0.999 3;在1.0、50.0、100μg/kg3个添加水平的平均加标回收率为87%~99%,相对标准偏差为1.9%~3.9%;方法检出限为0.3μg/kg,定量下限为1.0μg/kg。该方法简便、灵敏、准确、可靠,适用于禽蛋中头孢噻肟药物残留的分析。     

三聚氰胺-Cu2+-ANS三元络合物荧光光谱法检测超痕量三聚氰胺

利用荧光光谱法研究了三聚氰胺(MEL)和Cu2+与8-苯胺-1-萘磺酸(ANS)的相互作用.研究表明,MEL和Cu2+均对ANS有荧光猝灭作用,且猝灭机理均为静态猝灭.计算了表观结合常数和结合位点数.Cu2+的引入使得MEL猝灭ANS荧光的效果急剧增强,体系的相对荧光峰强与MEL浓度(1×10-10～1×10-5 mol/L)的对数值呈良好的线性关系,三聚氰胺的检出限为3.8×10-11 mol/L.紫外、荧光、三维荧光光谱的结果表明,MEL及Cu2+对ANS的荧光猝灭为协同作用,三者形成了三元络合物.本研究建立了荧光光谱检测超痕量三聚氰胺的新方法,为奶粉、乳制品中三聚氰胺的检测提供了新思路.     

气相色谱法测定化妆品中二甘醇的含量及其测量不确度评定

采用气相色谱法测定了化妆品中的二甘醇,并用计量学方法对测量不确定度进行了评定。结果显示,二甘醇含量在0.01~0.1 mg/mL范围内与色谱峰面积呈线性关系,线性相关系数为0.999 9,检测限为0.41μg/mL,不同类别的3种样品中二甘醇测定结果的相对标准偏差在0.24%~1.52%范围内(n=6),平均回收率在93.65%~104.36%之间。当啫喱水样品中二甘醇的测定结果为48.1 mg/kg时,其扩展不确定度为1.4 mg/kg。该方法可用于化妆品中二甘醇含量的质量控制。     

检测痕量Hg~(2+)的DNA电化学生物传感器

通过自组装方法将修饰有二茂铁基团的富T序列DNA分子(DNA-Fc)固定在金电极表面,得到了一种基于DNA修饰电极的电化学汞离子(Hg2+)传感器.当溶液中有Hg2+存在时,Hg2+可与修饰电极上DNA的T碱基发生较强的特异结合,形成T-Hg2+-T发卡结构,使DNA分子构象发生改变,其末端具有电化学活性的二茂铁基团远离电极表面,电化学响应随之发生变化.示差脉冲伏安法(DPV)结果显示:DNA末端二茂铁基团的还原峰在0.26V(vs饱和甘汞电极(SCE))附近,峰电流随溶液中Hg2+浓度的增加而降低;Hg2+浓度范围在0.1nmol·L-1-1μmol·L-1时,电流相对变化率与Hg2+浓度的对数呈现良好的线性关系.该修饰电极对Hg2+的检测限为0.1nmol·L-1,可作为痕量Hg2+检测的电化学生物传感器.干扰实验也表明,该传感器对Hg2+具有良好的特异性与灵敏度.     

N-邻羟苄基氨基酸的合成、表征及抑菌活性

将水杨醛、溴代水杨醛及二溴代水杨醛分别与4种L-α-氨基酸进行缩合反应生成相应席夫碱,不经分离直接加硼氢化钠将其还原制得N-邻羟苄基氨基酸类化合物(3)。 化合物的结构经IR、¹H NMR和元素分析测试技术表征确认。 测得化合物3在质量分数为0.05%时,对金黄色葡萄球菌的抑菌率为100％,对白色念珠菌有较强的抑菌活性,对大肠杆菌有一定的抑菌活性。 氨基酸的碳链R的结构是影响化合物抑菌活性的关键因素,不同烷基R对白色念珠菌和大肠杆菌抑菌活性增强的顺序为CH(CH₃)₂＞CH₃,CH₂CH(CH₃)₂＞H,苯环上引入溴原子对目标化合物的抑菌活性影响不明显。