一个新型钌(II)配合物对F－的双重光谱识别

采用紫外-可见光谱和荧光光谱滴定方法研究了钌(II)配合物[Ru(bpy)(H2iip)2](ClO4)2 [bpy＝2,2’-联吡啶, H2iip＝2-吲哚基-咪唑并[4,5-f][1,10]-邻菲罗啉]在DMSO溶液中对卤素离子的识别性质. 结果表明该配合物能比色和荧光双重光谱高选择性识别F－.     

New bifunctional initiator for use in anionic polymerizations

The synthesis is described of narrow distribution polystyrenes initiated by the 2,7-dimethyl-3,6-diphenyl-octane dianion (DDO²⁻). DDO²⁻ was synthesized via electron transfer from lithium or potassium metal to 3-methyl-2-phenyl-1-butene (MPB) in tetrahydrofuran at temperatures between −78 and −100 °C. In contrast to the analogous α-methyl styrene, there was no evidence of MPB polymerization. The structure of DDO²⁻ was demonstrated by ¹H and ¹³C NMR, as well as gas chromatography/mass spectrometry characterization of the DDO²⁻ protonation and methylation products. In addition, kinetic studies were performed by ultraviolet–visible spectrophotometry for the determination of the stability of this anion in comparison with other similar species. The initiation of styrene by DDO²⁻ led to narrow molecular weight polymers, as shown by size exclusion chromatography. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2108–2115, 2002     

Oxides of long carbon chains: Results obtained on IR and UV-vis absorptions

The IR and UV-vis absorptions of oxides of long carbon chains trapped in cryogenic matrices were investigated experimentally and theoretically. Some of the IR-lines were assigned to the oxides of certain carbon chains using the method of isotopic substitution of matrix material (¹⁶O₂/¹⁸O₂, ¹²CO/¹³CO) and the technique of selective UV-vis photo-bleaching. Our data, along with quantum chemical calculations suggest that the wavelength positions of the major UV-vis and IR absorptions of the oxides C_nO, OC_nO, and of the parent carbon chains C_n are located in close vicinity.     

UV-Visible Absorption Characteristics of TEOS-Derived and Cr-Doped Silica Sonogels Aged in Different pH Solutions and Heat Treated up to 600°C

Cr-doped xerogels were obtained by sol-gel process from the acid-catalyzed and ultrasound-stimulated hydrolysis of tetraethoxysilane (TEOS) with addition of CrCl₃6H₂O in water solution during the liquid step of the process. The gels were aged immersed in different pH solutions for about 30 days, after that they were allowed to dry. The samples were annealed at temperatures ranging from 40 to 600°C and analyzed by UV-visible absorption spectroscopy. Cr³⁺ is the preferable oxidation state of the chromium ion in the gels annealed up to 250–300°C, in the case of aging in solutions of pH = 5 and 11. A high UV absorption below 320 nm, due to the host gel, and different absorption bands, depending on the temperature, due to the chromium ion were observed in the xerogels at temperatures below 250°C, in the case of aging in solutions of pH = 1 and 2. These absorption bands have not been assigned. Above 300°C up to 600°C, Cr⁵⁺, and possibly Cr⁶⁺, are the preferable oxidation states of the chromium ion independent of the pH of the aging solution, so the xerogels turn to a yellowish appearance in all cases.     

Identification of Superoxide O2- during Thermal Decomposition of Molten KNO3-NaNO2-NaNO3 Salt by Electron Paramagnetic Resonance and UV-Vis Absorption Spectroscopy

On account of excellent thermal physical properties, molten nitrates/nitrites salt has been widely employed in heat transfer and thermal storage industry, especially in concentrated solar power system. The thermal stability study of molten nitrate/nitrite salt is of great importance for this system, and the decomposition mechanism is the most complicated part of it. The oxide species O₂^2- and O₂^- were considered as intermediates in molten KNO₃-NaNO₃ while hard to been detected in high temperature molten salt due to their trace concentration and low stability. In this work, the homemade in situ high temperature UVVis instrument and a commercial electron paramagnetic resonance were utilized to supply evidence for the formation of superoxide during a slow decomposition process of heat transfer salt (HTS, 53 wt% KNO₃/40 wt% NaNO₂/7 wt% NaNO₃). It is found that the superoxide is more easily generated from molten NaNO₂ compared to NaNO₃, and it has an absorption band at 420-440 nm in HTS which red shifts as temperature increases. The band is assigned to charge-transfer transition in NaO₂ or KO₂, responsible for the yellow color of the molten nitrate/nitrite salt. Furthermore, the UV absorption bands of molten NaNO₂ and NaNO₃ are also obtained and compared with that of HTS.     

New approaches towards the synthesis and characterization of alkoxy substituted spirobifluorenes and spirosilabifluorenes for organic optoelectronics

Alkoxy substituted spirobifluorene derivatives namely 2,2′,7,7′-tetrabromo-3,6-bis(methoxy)-9,9′spirobifluorene (MSBF), 2,2′,7,7′-tetrabromo-3,6-bis(ethoxy)-9,9′spirobifluorene (ESBF), 2,2′,7,7′-tetrabromo-3,6-bis(butoxy)-9,9′spirobifluorene (BSBF), 2,2′,7,7′-tetrabromo-3,3′,6,6′-tetra(methoxy)-9,9′-spiro-9-silabifluorene (MSSiBF) and their key intermediates have been synthesised successfully. All compounds have been fully characterised by ¹H and ¹³C NMR, FTIR, UV-visible spectroscopy, MS spectrometry. TGA analysis revealed good thermal stability. The systematic investigation on the solubility, thermostability and photophysical property of synthesized compound showed that alkoxy substituted spirobifluorene were unique in rigidity and have wide range of applications in molecular electronics and can be used as building units for optoelectronics material.     

Acidichromism and Ionochromism of Luteolin and Apigenin,the Main Components of the Naturally Occurring Yellow Weld: A Spectrophotometric and Fluorimetric Study

Luteolin and apigenin, extracted from Reseda luteola L., were spectrophotometrically and fluorimetrically studied. The spectra were investigated as a function of pH in methanol/water solutions (1/2, v/v) in the 2–12 pH range. The absorption spectra markedly shifted to the red by increasing the pH. Three acid–base dissociation steps were detected for luteolin (pK _a = 6.9; 8.6; 10.3) and two for apigenin (pK _a = 6.6; 9.3). Fluorescence emission was very weak or undetectable (Φ _F < 10⁻⁴) in acidic solution, but increased in intensity with increasing the pH. Both molecules exhibited a great propensity towards complex formation with metal ions, with association constants on the order of 10⁵–10⁷ for the first complexation step; in the presence of excess Al³⁺ ions, multiple equilibria were detected. A marked fluorescence enhancement was observed upon complexation with Al³⁺ ions (Φ _F ∼ 1 for luteolin and ∼10⁻² for apigenin).     

单分散Au纳米粒子液相合成与快速检测三聚氰胺——本科生综合化学实验

利用Au纳米粒子与三聚氰胺相互作用产生的颜色变化来快速评估牛奶中三聚氰胺的含量,采用透射电子显微镜表征Au纳米粒子与三聚氰胺作用前后的形貌变化,通过用紫外-可见吸收光谱数据绘制标准工作曲线来定量测定牛奶中三聚氰胺的含量。该实验贴近生活,学以致用,同时也有助于学生掌握无机化学和分析化学基本操作,对增强学生分析解决问题的能力,提升学生的科研素养也有帮助。     

四(对－硝基)苯基卟啉锰配合物的光谱电化学性质

应用循环伏安、现场紫外可见光谱和红外光谱电化学技术确认了四(对-硝基)苯基卟啉锰配合物产生不同氧化态锰卟啉的电位及其电子光谱和振动光谱特征,发现卟啉周环上硝基的还原发生在Mn²⁺还原之后,金属价态变化敏感带出现在1597、1523、1207、825和806cm^-1附近。     

ELECTROCHEMICAL SYNTHESIS AND PROPERTIES OF POLY(AZURE B)*

A blue poly(azure B) film has been synthesized using repeated potential cycling between -0.25 and 1. 10 V (versusSCE). The electrolytic solution consisted of 2.5 mmol dm~(-3) azure B, 0.5 mol dm~(-3) NaCl and 0.2 mol dm~(-3) NaH_2PO_4 at the pHrange of 2.0 to 11.0. The in situ visible spectrum during electrolysis of azure B shows that the intensity at 740 nm peakincreases with increasing numbers of potential cycles, which is attributable to the formation of poly(azure B). Thewavelength of its corresponding absorption peak is 98 nm longer than that of azure B. The polymerization rate is stronglyaffected by pH values. The anodic peak potential and cathodic peak potential of the poly(azure B) in a solution of pH 3.0 arenot affected by increasing the scan rate from 25 to 600 mV s~(-1). Poly(azure B) has good electrochemical reversibility and fastcharge transfer characteristic in the pH range of 2.0 and 11.0. The conductivity of poly(azure B) is 1.5×10~(-4) S cm~(-1).According to the differences between FTIR spectra of poly(azure B) and azure B, an electrochemical polymerizationmechanism of azure B is proposed in this paper.