荧光酮取代基对碳纳米管协同增效作用的影响研究

以金属离子(Pb2+、Mn2+)与荧光酮(苯基荧光酮、水杨基荧光酮、邻氯苯基荧光酮)的显色体系为模型,在阳离子表面活性剂十六烷基三甲基溴化铵(CTMAB)的存在下,研究了显色剂荧光酮不同的取代基对碳纳米管协同增效作用的影响。结果表明,碳纳米管作为一种新型增效剂,与荧光酮产生π-π作用,使荧光酮类显色体系的灵敏度得到提高。3种荧光酮的增敏强度为ΔA苯基荧光酮ΔA水杨基荧光酮ΔA邻氯苯基荧光酮。该文从空间位阻、氢键以及取代基的电子效应等方面进行了机理的探讨。水杨基荧光酮和邻氯苯基荧光酮由于邻位取代基的存在,增加了荧光酮分子与碳纳米管之间π-π作用的空间位阻,导致显色体系的增敏强度较小;与带有—Cl吸电子基团的邻氯苯基荧光酮相比,水杨基荧光酮上的供电子基团—OH可与碳纳米管上的含氧基团形成氢键,由于氢键的作用以及电子效应的不同导致了增敏效应的差异。对体系的实验条件进行优化,得出最佳测锰体系的线性范围为0.04~0.56 mg/L,回归方程为A=0.016+1.541C(mg/L),表观摩尔吸光系数ε=9.45×104L/(mol.cm),r=0.997。利用该体系对自来水中的锰进行了测定,结果令人满意。     

Problems,possibilities and limitations of inductively coupled plasma atomic emission spectrometry in the determination of platinum,palladium and rhodium in samples with different matrix composition

The economic and geological importance of platinum group of elements has led to the development of analytical methods to quantify them in different types of samples. In the present paper the quantitative information for spectral interference in radial viewing 40.68 MHz inductively coupled plasma atomic emission spectrometry in the determination of Pt, Pd and Rh in the presence of complex matrix, containing Al, Ca, Fe, Mg, Mn, P and Ti as matrix constituents was obtained. The database was used for optimum line selections. By using the selected analysis lines the following detection limits in ng g^− 1 were obtained: Pt 1700, Pd-1440, Rh-900. The reached detection limits determine the possibilities and limitation of the direct ICP-AES method in the determination of Pt, Pd and Rh in geological and environmental materials. The database for spectral interferences in the presence of aluminum can be used for the determination of platinum group of elements in car catalysts.     

Reaction of 3-aminoquinoline-2,4-diones with isothiocyanic acid—an easy pathway to thioxo derivatives of imidazo[1,5-c]quinazolin-5-ones and imidazo[4,5-c]quinolin-4-ones

3-Amino-1H,3H-quinoline-2,4-diones react with thiourea or potassium thiocyanate in boiling acetic acid to give novel 2,3-dihydro-3-thioxoimidazo[1,5-c]quinazolin-5(6H)-ones in high yields. However, if the starting compounds are substituted with a benzyl group at position 3, a C-debenzylation proceeds to give 2,3-dihydro-2-thioxo-1H-imidazo[4,5-c]quinolin-4(5H)-ones. According to a proposed reaction mechanism, a molecular rearrangement of the primarily formed mono-substituted thiourea takes place. All compounds were characterized by ¹H, ¹³C and ¹⁵N NMR and IR spectroscopy as well as by mass spectrometry.     

New epoxy thermosets modified with hyperbranched poly(ester-amide) of different molecular weight

The influence of hydroxy-functionalized hyperbranched poly(ester-amide) (HBP) of different molecular weight on the curing process of diglycidylether of bisphenol A (DGEBA) was studied using methyltetrahydrophthalic anhydride (MTHPA) as curing agent. By Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FTIR) the curing reaction was monitored and the covalent incorporation of the modifier in the matrix was proved. By thermomechanical analysis (TMA) the reduction of the contraction after gelation on changing the HBP proportion was observed. The incorporation of HBP increased the glass transition temperature (T_g) and reduced the overall shrinkage. The modified materials showed a higher thermal degradability than neat DGEBA thermosets allowing reworkability. Thermal expansion coefficient, Young’s modulus, impact strength and microhardness were improved. The water uptake behavior was also evaluated.     

Synthesis of aromatic tetracyclic tin compounds by template and transmetallation reactions: Alkyl vs aryl migration from tin to nitrogen

The syntheses of [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]diphenyltin (1) and [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]dichloro-phenyl-stannate (2) by template reactions using 3,5-di-tert-butylcatechol, aqueous ammonia and SnPh₂Cl₂ are reported. We also report the syntheses of compounds 2, [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]trichloro-stannate (4), [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)methylamine]chloro-methyltin (5), and [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)-n-butylamine]n-butyl-chlorotin (6) and [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]n-butyl-dichloro-stannate (7), performed by transmetallation reactions of the octahedral zinc coordination compound Zn[3,5-di-tert-butyl-1,2-quinone-(3,5-di-tert-butyl-2-hydroxy-1-phenyl)imine]₂ (3) with SnPhCl₃ or SnPh₂Cl₂, SnCl₄, SnMe₂Cl₂, Sn(nBu)₂Cl₂ and Sn(nBu)Cl₃, respectively. The X-ray diffraction structures of compounds 1, 2, 4 and 6 are reported. The transmetallation reactions with Sn(alkyl)₂Cl₂ afforded pentacoordinated tin compounds, where an alkyl group migrated from tin to nitrogen, while similar reactions with Sn-Ph compounds did not present any phenyl group migration.     

Antimony-Carbon bond activation in a Pt(II) complex: The crystal structure of [Pt(9S3)(SbPh3)(Ph)](PF6)·CH3NO2

The complex [Pt(9S3)(SbPh₃)(Ph)](PF₆) forms directly from [Pt(9S3)(SbPh₃)₂](PF₆)₂ during the room temperature crystallization of the latter in nitromethane. The crystal structure shows a five-coordinate Pt(II) center containing the tridentate thiacrown ligand, a Sb donor from the triphenylstibine ligand, and a σ-coordinating phenyl group. The phenyl group forms via Sb-C bond cleavage from one of the SbPh₃ ligands in the bis complex.     

Biodegradable amphiphilic block copolymers containing functionalized PEO blocks:Controlled synthesis and biomedical potentials

A series of controllable amphiphilic block copolymers composed of poly(ethylene oxide)(PEO) as the hydrophilic block and poly(ε-caprolactone)(PCL) as the hydrophobic block with the amino terminal group at the end of the PEO chain(PCL-b-PEO-NH2) were synthesized.Based on the further reaction of reactive amino groups,diblock copolymers with functional carboxyl groups(PCL-b-PEO-COOH) and functional compounds RGD(PCL-b-PEO-RGD) as well as the triblock copolymers with thermosensitive PNIPAAm blocks(PCL-b-PEO-b-P...     

Prediction of retention indices. VI: Isothermal and temperature-programmed retention indices,methylene value,functionality constant,electronic and steric effects

The Kováts retention index system with n-alkanes as reference standards has properties not fully explored when single, isolated or stand-alone analytes are analyzed by isothermal gas chromatography. When a homologous series of analytes are analyzed by either linear or non-linear temperature-programmed gas chromatography, the retention data of the entire series can be treated systematically to produce an I vs. Z plot that is linear, thereby giving insight into the relationship between chemical structure and retention index. Dead time t_M is both instrument and temperature dependent. With no dead time t_M adjustment, the retention indices of analytes calculated from experimental retention times by the method of either linear or logarithmic interpolation give statistically identical values. Linear regression analysis of the data shows the slope as methylene value (A) and intercept as functionality constant or group retention factor (GRF) of the homologous series. The A and (GRF) values vary with chemical structures, intermolecular electronic and steric interactions, and polarity of column liquid phases, and can link gas chromatographic retention index to chemical structure. Examples of the influence of molecular electronic effects and steric effects on retention index are given and discussed.     

Facile synthetic pathway to β-hydroxy-β-trifluoromethyl imines and their derivatives

Synthetic approach based on mediated addition of different trifluoromethylated building blocks to selected acyclic imines giving access to a variety of β-hydroxy-β-trifluoromethyl imines are elaborated. A reaction between fluorinated adducts and imines proceed easily giving the condensation products in good to excellent yields. β-Hydroxy-β-trifluoromethyl imines possessing trifluoromethyl group and exhibiting strong intramolecular hydrogen bonding are great precursors to different β-hydroxy-β-trifluoromethyl ketones and alcohols.