Analysis of diphenylamine and impurities using monolithic column with electrochemical detection

A high-performance liquid chromatographic (HPLC) method with electrochemical detection (ED) using a monolithic column was developed and validated for the simultaneous quantitative determination of aniline, 2-aminobiphenyl, and 4-aminobiphenyl in diphenylamine samples. The proposed HPLC method provides a shorter analysis time as compared to previously reported ones (less than 4 min). Method validation was performed in terms of sensitivity, repeatability, linearity, accuracy, detection limit, and quantification limit. It is found that the method has high accuracy and precision. The limits of detection obtained were 0.23 ng/mL for aniline and 0.30 ng/mL for 2-aminobiphenyl, 4-aminobiphenyl, and diphenylamine. All authors contributed equally to this work. The text was submitted by the authors in English.     

Synthesis of thieno[3,4-c] and thieno[3,2-c][2,1]benzothiazepines

Starting from [4,3-c] and [3,2-c] methyl chlorosulfonylthiophenecarboxylates the synthesis of ketones 7 and 8 is described. These compounds are the first two representatives of the new thieno[3,4-c] and thieno-[3,2-c][2,1]benzothiazepine ring systems. The formation of methyl 3-chlorosulfonylthiophene-2-carboxy-late is also revised.     

Extraction-spectrofluorimetric determination of cadmium with diethyldithiocarbamate and calcein in non-aqueous media

Cadmium (7–80 ng ml^?1) is extracted with diethyldithiocarbamate into chloroform from aqueous media, at pH 11–12 and the fluorescent complex is developed by addition of a calcein solution in dimethylformamide. The method is applied to the determination of cadmium in waste waters, high-purity metals and zinc ores.     

Magnetism of cyano-bridged Ln3+-M3+ complexes. Part II: one-dimensional complexes (Ln3+ = Eu, Tb, Dy, Ho, Er, Tm; M3+ = Fe or Co) with bpy as blocking ligand

The reaction of Ln(NO3)3(aq) with K3[Fe(CN)6] or K3[Co(CN)6] and 2,2'-bipyridine in water/ethanol led to 13 one-dimensional complexes: trans-[M(CN)4(mu-CN)2Ln(H2O)4(bpy)]n.4nH2O.1.5nbpy (Ln = Eu3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Lu3+; M = Fe3+, Co3+). The structures for [EuFe]n (1), [TbFe]n (2), [DyFe]n (3), [HoFe]n (4), [ErFe]n (5), [TmFe]n (6), [LuFe]n (7), [EuCo]n (8), [TbCo]n (9), [DyCo]n (10), [HoCo]n (11), [ErCo]n (12), and [TmCo]n (13) have been solved: they crystallize in the triclinic space group P and are isomorphous. They exhibit a supramolecular architecture created by the interplay of coordinative, hydrogen bonding, and pi-pi interactions. A stereochemical study of the eight-vertex polyhedra of the lanthanide ions, based on continuous shape measures, is presented. The Ln3+-Fe3+ interaction is antiferromagnetic in [DyFe]n and [TbFe]n. For [EuFe]n, [HoFe]n, [ErFe]n, and [TmFe]n, there is no sign of any significant interaction. The magnetic behavior of [DyFe]n suggests the onset of weak long-range ferromagnetic ordering at 2.5 K.     

Hydroxy‐ and chloro‐ dediazoniation of 2‐ and 3‐ methylbenzenediazonium tetrafluoroborate in aqueous solution

We have measured the rates and product yields of dediazoniation of 2‐ and 3‐methylbenzenediazonium tetrafluoroborate in the presence and absence of electrolytes like HCl, NaCl, and CuCl₂ using a recently reported methodology that allows simultaneous determination of product concentrations and rates of product formation and, indirectly, loss of starting material. Activation parameters were also obtained: enthalpies of activation are high, and entropies of activation are positive. All results are consistent with a heterolytic mechanism involving the fragmentation of the arenediazonium ion into a very reactive phenyl cation. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 73–82, 1999     

The potent anticancer compound ecteinascidin‐743 (ET‐743) as its 2‐propanol disolvate

Single crystals of the title compound, C₃₉H₄₃N₃O₁₁S·2C₃H₈O, have been obtained from 2‐propanol/water solutions. ET‐743 belongs to the group of ecteinascidins (ETs), which is a family of novel marine tetra­hydro­iso­quinoline derivatives characterized by a monobridged pentacyclic skeleton. Three large princi­pal planar groups are observed in the three‐dimensional structure of the ET‐743 mol­ecule, corresponding to three aromatic units which are nearly perpendicular to each other. In the crystal, the methoxy group on the large fused ring system adopts an anti conformation with respect to the S atom, thus presenting the same conformation as that found in solution.     

Cu acetate complexes involving N,N,O donor Schiff base ligands: Mono-atomic oxygen bridged dimers and alternating chains of the dimers and Cu2(OAc)4

Two tridentate N,N,O donor Schiff bases, HL¹ (4-(2-ethylamino-ethylimino)-pentan-2-one) and HL² (3-(2-amino-propylimino)-1-phenyl-butan-1-one) on reaction with Cu^II acetate in presence of triethyl amine yielded two basal-apical, mono-atomic acetate oxygen-bridging dimeric copper(II) complexes, [Cu₂L¹₂(OAc)₂] (1), [Cu₂L²₂(OAc)₂] (2). Whereas two other similar tridentate ligands HL³ (4-(2-amino-propylimino)-pentane-2-one) and HL⁴ (3-(2-amino-ethylimino)-1-phenyl-butan-1-one) under the same conditions produced a mixture of the corresponding dimers and a one-dimensional alternating chain of the dimer and copper acetate moiety, [Cu₄L³₂(OAc)₆]_n (3) and [Cu₄L⁴₂(OAc)₆]_n (4), formed by a very rare μ₃ bridging mode of the acetate ion. All four complexes (1–4) have been characterized by X-ray crystallography. The isotropic Hamiltonian, H = −JS₁S₂ has been used to interpret the magnetic data. Magnetic measurements of 1 and 2 in the temperature range 2–300 K reveal a very weak antiferromagnetic coupling for both complexes (J = −0.56 and −1.19 cm⁻¹ for 1 and 2, respectively).