Analysis of aromatic amines by high-performance liquid chromatography with pre-column derivatization by 2-(9-carbazole)-ethyl-chloroformate

2-(9-Carbazole)-ethyl-chloroformate (CEOC), a novel pre-column fluorescence derivatization reagent, has been developed for the analysis of aromatic amines. Taking five monocyclic aromatic amines (o-toluidine, aniline, 3,4-dimethylaniline, N-ethyl-p-toluidine, and p-phenylenediamine) as testing compounds, derivatization conditions such as pH of borate buffer, reaction time and fluorescent tagging reagent concentration have been investigated. By a one-step procedure, CEOC reacts readily with the aromatic amines to form stable derivatives with excitation and emission wavelengths, respectively, at 293 and 360 nm. This derivatization reaction could be finished within 20 min even at room temperature. The peak shapes of the derivatized aromatic amines can be improved greatly without any addition of competition amines into the mobile phase. Furthermore, this method can offer excellent quantitative precision with high tolerance of the matrix of samples. (C) 2003 Elsevier B.V. All rights reserved.

Synthesis of novel star-like hyperbranched polymers with poly(amido amine) core and poly(L-lysine) shell

Hyperbranched poly(amido amine)s containing vinyl and hydroxyl groups were successfully synthesized via Michael addition polymerization of triacrylamide (TT) and 3-amino-1,2-propanediol (APD) with equal molar ratio in feed. H-1, C-13 and HSQC NMR techniques were used to clarify the structure of hyperbranched polymers and polymerization mechanism.

Nanoscale-enhanced Ru(bpy)(3)(2+) electrochemiluminescence labels and related aptamer-based biosensing system

A unique multilabeling at a single-site protocol of the Ru(bpy)(3)(2+) electrochemiluminescence (ECL) system is proposed. Nanoparticles (NPs) were used as assembly substrates to enrich ECL co-reactants of Ru(bpy)(3)(2+) to construct nanoscale-enhanced ECL labels. Two different kinds of NP substrates [including semiconductor NPs (CdTe) and noble metal NPs (gold)] capped with 2-(dimethylamino)ethanethiol (DMAET) [a tertiary amine derivative which is believed to be one of the most efficient of co-reactants of the Ru(bpy)(3)(2+) system] were synthesized through a simple one-pot synthesis method in aqueous media.

Alternating Copolymerization of Cyclohexene Oxide and Carbon Dioxide Catalyzed by Noncyclopentadienyl Rare-Earth Metal Bis(alkyl) Complexes

The syntheses of several dialkyl complexes based on rare-earth metal were described. Three beta-diimine compounds with varying N-aryl substituents (HL1 = (2-CH3O(C6H4))N=C(CH3)CH=C(CH3)NH(2-CH3O(C6H4)), HL2 = (2,4,6-(CH3)(3) (C6H2))N=C(CH3)CH=C(CH3)NH(2,4,6-(CH3)(3)(C6H2)), HL3 = PhN=C(CH3)CH(CH3) NHPh) were treated with Ln(CH2SiMe3)(3)(THF)(2) to give dialkyl complexes L(1)Ln (CH2SiMe3)(2) (Ln = Y (1a), Lu (1b), Sc (1c)), L(2)Ln(CH2SiMe3)(2)(THF) (Ln = Y (2a), Lu (2b)), and (LLu)-Lu-3(CH2SiMe3)(2)(THF) (3). All these complexes were applied to the copolymerization of cyclohexene oxide (CHO) and carbon dioxide as single-component catalysts.

Thiophene-NPN Ligand Supported Rare-Earth Metal Bis(alkyl) Complexes. Synthesis and Catalysis toward Highly trans-1,4 Selective Polymerization of Butadiene

A series of new rare-earth metal bis(alkyl) complexes [L(1-3)Ln(CH2SiMe3)(2)(THF)(n)] (L-1 = MeC4H2SCH2NC6H4(Ph)(2)P=NC6H2Me3-2,4,6: Ln = Sc, n = 1 (1a); Ln = Lu, n = 1 (1b); L-2 = MeC4H2SCH2NC6H4(Ph)(2)P=NC6H3Et2-2,6: Ln = Sc, n = 1 (2a); Ln = Lu, n = 1 (2b); Ln = Y, n = 1 (2c); L-3 = MeC4H2SCH2NC6H4(Ph)(2)P=(NC6H3Pr2)-Pr-i-2,6: Ln = Sc, n = 0 (3a)) and (LSc)-Sc-4(CH2SiMe3)(2()THF) (4a) (L-4 = C6H5CH2NC6H4(Ph)(2)P=NC6H3Et2-2,6) have been prepared by reaction of rare-earth metal tris(alkyl)s with the corresponding HL1-4 ligands via alkane elimination.

Tridentate CCC-Pincer Bis(carbene)-Ligated Rare-Earth Metal Dibromides. Synthesis and Characterization

The first xylene-bridged bis(N-heterocyclic carbene) (bis(NHC))-ligated CCC-pincer rare-earth metal dibromides (PBNHC)LnBr(2)(THF) (PBNHC = 2,6-(2,4,6-Me3C6H2NCHCHNCCH2)(2)C6H3; 1: Ln = Sc; 2: Ln = Lu; 3: Lu = Sm) were prepared by in situ treatment of a THF suspension of 2,6-bis(1-mesitylimidazolium methyl)-1-bromobenzene dibromides ((PB-NHC-Br) center dot 2HBr) and lanthanide trichlorides (LnCl(3)) with dropwise addition of nBuLi at room temperature.

New rare earth metal bis(alkyl)s bearing an iminophosphonamido ligand. Synthesis and catalysis toward highly 3,4-selective polymerization of isoprene

Newrareearth metal bis(alkyl) complexes [(NPNPh)Ln(CH2SiMe3)(2)(THF) (NPNPh:N(Ph)PPh2=NC6H2Me3-2,4,6; Ln = Sc (3a), Ln = Y (3b), Ln = Lu (3c)) and [(NPNPy)Sc(CH2SiMe3)(2)(THF)1 (NPNPY = N(Py)PPh2=NC6H2Me3-2,4,6) (3d)) have been prepared via protonolysis reaction between rare earth metal tris(alkyl)s and the corresponding iminophosphonamines. Complexes 3a-d are analogous monomers of THF solvate. Each metal ion coordinates to a eta(2)-chelated NPN ligand and two cis-located alkyl groups, adopting tetrahedron geometry.

Extraction kinetics of thorium(IV) with primary amine N1923 in sulfate media using a constant interfacial cell with laminar flow

Extraction kinetics of thorium(IV) with primary amine N1923 in sulfate media has been investigated by a constant interfacial cell with laminar flow. Studies of interfacial tension and effects of the stirring rate, temperature, and specific interfacial area on mass transfer rate show that the most probable reaction zone takes place at the liquid-liquid interface. According to the experimental data correlated as a function of the concentration of the relevant species involved in the extraction reaction, the rate equation of extracting thorium has been obtained as follows: -d[Th(IV)]((o))/dt = 10(-3.10)center dot[Th(IV)](0.89)center dot[(RNH3)(2)SO4](0.74).

Construction and Photoluminescence of Monophase Hybrid Materials Derived from a Urea-Based Bis-Silylated Bipyridine

A urea-based bis-silylated bipyridine ligand derived from 4,4'-diamino-2,2'-bipyridine has been prepared. Organic-inorganic hybrid materials with a high loading of lanthanide 2,2-bipyridine moieties were obtained by using the silylated bipyridine as the only siloxane network precursor in the presence of lanthanide ions (or lanthanide complexes). The in-situ formation of lanthanide complexes from lanthanide ions and the silylated bipyridine during the sol-gel processing was confirmed by the luminescence behavior of the obtained hybrid materials and that of the corresponding pure lanthanide complex [Ln(bpy)(2)Cl-3 center dot 2H(2)O].

Hydrothermal Synthesis, Structures, and Luminescent Properties of Seven d(10) Metal-Organic Frameworks Based on 9,9-Dipropylfluorene-2,7-Dicarboxylic Acid (H(2)DFDA)

A series of Zn(II) and Cd(II) metal-organic frameworks, namely, [Zn(DFDA)] (1), [Cd(DFDA)(C2H5OH)] (2), [Zn-2(DFDA)(2)(L-1)(2)](2) center dot 3H(2)O (3), [Cd-2(DFDA)(2)(L-1)(2)] (4), [Zn(DFDA)(L-2)] (5), [Cd(DFDA)(L-2)(DMF)] (6), and [Zn(DFDA)(L-3)] (7) (where DFDA = 9,9-dipropylfluorene-2,7-dicarboxylate anion, L-1 = 1,4-bis(imidazol-1-ylmethyl)benzene, L-2 = 1,1'-(1,4-butanediyl) bis(imidazole), L-3 = 2,2'-bipyridine) have been synthesized under hydrothermal conditions and structurally characterized. Compound 1 exhibits a three-dimensional (3D framework containing one-dimensional (1D) Zn(II)-O clusters, with (4(8).6(7)) topology. Compound 2 contains hydrophobic channels built from infinite 1D Cd(II)-O clusters, with (4(8).5(4).6(3)) topology.

Determination of isocyanates by capillary electrophoresis with tris(2,2 '-bipyridine) ruthenium(II) electrochemiluminescence

CE with tris(2,2'-bipyridyl) ruthenium(II) (Ru(bpy)(3)(2+)) electrochemiluminescence (ECL) detection for the quantitative determination of isocyanates was first reported. Hexamethylene diisocyanate (HDI) and hexyl isocyanate (HI) were used as the model analytes. Commercially available N,N-diethyl-N'-methylethylenediamine was used as the derivatization reagent. It has both a secondary amine group and a tertiary amine group. The secondary amine group can quantitatively react with isocyanate group, and the tertiary amine group can react with Ru(bpy)(3)(2+) to produce strong ECL signal for sensitive detection. The derivatization reaction was almost instantaneous and is much faster than other reported derivative reactions using other derivative reagents.

Effect of hydroxyl and amino groups on electrochemiluminescence activity of tertiary amines at low tris(2,2 '-bipyridyl)ruthenium(II) concentrations

ECL of several amines containing different numbers of hydroxyl and amino groups was investigated. N-butyldiethanolamine is found to be more effective than 2-(dibutylamino)ethanol at gold and platinum electrodes, and is the most effective coreactant reported until now. Surprisingly, ECL intensities of monoamines, such as 2-(dibutylamino)ethanol and N-butyldiethanolamine, are much stronger than that of diamines including N,N,N',N'-tetrakis-(2-hydroxyethyl)-ethylenediamine and N,N,N',N'-tetrakis-(2-hydroxypropyl)ethlenediamine. The striking contrast between ECL signals of the investigated monoamines and diamines may result from more significant side reactions of diamines, such as the intramolecular side reactions between oxidative amine cation radicals and reductive amine free radicals.

Dispersions of carbon nanotubes in sulfonated poly[bis(benzimidazobenzisoquinolinones)] and their proton-conducting composite membranes

A sulfonated poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI) possessing a conjugated pyridinone ring was shown to be effective for dispersing multiwalled carbon nanotubes (MWCNTs) in DMSO. The dispersions in which the SPBIBI to MWCNTs mass ratio was 4:1 demonstrated the highest MWCNTs concentrations, i.e., 1.5-2.0 mg mL(-1), and were found to be stable for more than six months at room temperature. Through casting of these dispersions, MWCNTs/SPBIBI composite membranes were successfully fabricated on substrates as proton exchange membranes for fuel cell applications and showed no signs of macroscopic aggregation. The properties of composite membranes were investigated, and it was found that the homogeneous dispersion of the MWCNTs in the SPBIBI matrix altered the morphology structures of the composite membranes, which lead to the formation of more regular and smaller cluster-like ion domains.

Synthesis and properties of soluble poly[bis(benzimidazobenzisoquinolinones)] based on novel aromatic tetraamine monomers

Four aromatic tetraamine monomers possessing flexible ether linkages were successfully synthesized by nucleophilic aromatic substitution of hydroquinone, 4,4'-dihydroxybiphenyl, 2,2'-bis(4-hydroxyphenyl)propane, and 2,7-dihydroxynaphthalene with 5-chloro-2-nitroaniline, followed by reduction, respectively. With these monomers, a new class of soluble poly[ bis(benzimidazobenzisoquinolinones)] was prepared by a one-step, high-temperature solution polycondensation. The resulting polymers were completely soluble in phenolic solvents and had high inherent viscosities ranging from 1.2 to 1.5 g dL(-1). These polymers had glass transition temperatures in the range of 427-449 degrees C. Thermogravimetric analysis showed that all polymers were thermally stable, with 5% weight loss recorded above 510 degrees C in nitrogen.

Synthesis and properties of water stable poly[bis(benzimidazobenzisoquinolinone)] ionomers for proton exchange membranes fuel cells

A novel sulfonated tetraamine, di(triethylammonium)-4,4'-bis(3,4-diaminophenoxy)biphenyl-3,3'-disulfonate (BAPBDS), was successfully synthesized by nucleophilic aromatic substitution of 4,4'-dihydroxybiphenyl with 5-chloro-2-nitroaniline, followed by sulfonation and reduction. A high-temperature polycondensation of sulfonated tetraamine, non-sulfonated tetraamine (4,4 -bis(3,4-aminophenoxy)biphenyl) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (a) or 4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianydride (b) gave the poly[bis(benzimidazobenzisoquinolinones)] ionomers SPBIBI-a(x) or SPBIBI-b(x), where x refers to the molar percentage of the sulfonated tetraamine monomer. Flexible and tough membranes of high mechanical strength were obtained by solution casting and the electrolyte properties of the polymers were intensively investigated. The ionomer membranes displayed excellent dimensional and hydrolytic stabilities.