A simple method of isolation of chloramphenicol in honey and its estimation by liquid chromatography coupled to electrospray ionization tandem mass spectrometry

To detect sub-ppb levels of the antibiotic chloramphenicol in honey matrix, a convenient method of extraction and measurement using liquid chromatography with detection by tandem mass spectrometry (LC/MS/MS) was developed. Honey samples fortified with chloramphenicol and isotopically labeled chloramphenicol were extracted using diatomaceous-based supported liquid-liquid extraction cartridges to generate a standard calibration curve. Four MS/MS transitions were used for quantification and four other transitions for confirmation of chloramphenicol. The limit of detection for chloramphenicol was 0.05 ng/g and the lower limit of quantification was 0.1 ng/g. Several commercial honey samples were analyzed for chloramphenicol content using this method.     

Fluorescent sensing of pyrophosphate and ATP in 100% aqueous solution using a fluorescein derivative and Mn

A new fluorescein derivative has been synthesized for the detection of pyrophosphate (PPi) and ATP in 100% aqueous solution. Chemosensor 1 in the presence of Mn²⁺ (2.5 equiv) displayed selective fluorescent enhancements with PPi and ATP at pH 7.4. among the anions examined. The association constant of 1 in the presence of Mn²⁺ with PPi and ATP was calculated as 4.2 × 10⁴ and 3.5 × 10⁴ M⁻¹.     

Simple but effective way to sense pyrophosphate and inorganic phosphate by fluorescence changes

A new fluorescent chemosensor based on the acridine-Zn(II) derivative effectively recognizes pyrophosphate and inorganic phosphate at pH 7.4. Acridine derivative 1 displayed a fluorescent quenching effect with pyrophosphate; on the other hand, a large fluorescent enhancement was observed with inorganic phosphate. [structure: see text].     

Crystal structure of indium(III) Schiff base complex

The title compound [In(C₂₂H₃₀N₄O₄)]Cl (I) bis[(N-salicylidene-N′-(2-hydroxyethyl)ethyleneediamine) indium(III) chloride is prepared, and its crystal structure is determined by single crystal X-ray diffraction at room temperature. The complex crystallizes in the monoclinic space group P2₁/n, a = 9.9704(6) ?, b = 24.9554(15) ?, c = 10.5707(6) ?, β = 116.46(2)°, V = 2354.6(2), Z = 4. The X-ray analysis reveals that the In^III ion is surrounded by four nitrogen and two oxygen atoms from two ligands leading to a distorted octahedral geometry. The molecule has the form of tongs at a junction point with the metal. Five membered rings adopt envelope conformation. In the crystal structure, the molecules are linked via N-H...Cl, O-H...O, O-H...Cl, and C-H...Cl intermolecular interactions. The structure is further stabilized by C-H...π (arene) interactions.     

Does a sterically bulky group occupy the equatorial site in trigonal bipyramidal phosphorus?

[structure: see text] The sterically bulky tert-butyl group occupies an apical position in trigonal bipyramidal phosphorus in the compound [CH2(6-t-Bu-4-Me-C6H2O)2]P(t-Bu)(1,2-O2C6Cl4) in contrast to the occupation of an equatorial position by the small methyl group in [CH2(6-t-Bu-4-Me-C6H2O)2]P(Me)(1,2-O2C6Cl4); this observation contradicts the familiar "apicophilicity rules" for trigonal bipyramidal phosphorus. Low-temperature solution 31P NMR spectra of [CH2(6-t-Bu-4-Me-C6H2O)2]P(R)(1,2-O2C6Cl4) (R = Me, Et, and n-Bu) show the presence of more than two isomers.     

Structural motifs in (t-butoxy) zirconium phosphinates,arsinates, and phosphates

Reaction of zirconium tetrakis(tert-butoxide) (1) with dicylohexylphosphinic acid in toluene leads to the dinuclear compound [Zr(mu,mu'-O(2)P(cycl-C(6)H(11))(2))(O-t-Bu)(3)](2) (2) in which the zirconium is pentacoordinated. An analogous reaction using diphenylphosphinic acid in tetrahydrofuran also leads to a dinuclear complex [Zr(mu,mu'-O(2)PPh(2))(THF)((O-t-Bu)(3)](2).C(6)H(5)CH(3) (3.C(6)H(5)CH(3)), in which zirconium is hexacoordinated. A novel exchange of tert-butoxy and phenoxy groups occurs when 1 is treated with diphenyl phosphate [(PhO)(2)PO(2)H] leading to the isolation of the exchange product [Zr(mu,mu'-O(2)P(O-t-Bu)(OPh))(mu-OPh)(O-t-Bu)(2)](2) (4). In contrast to the above, trinuclear zirconium compounds Zr(3(mu,mu'-O(2)AsMe(2))(2)(mu2,mu'-O(2)AsMe(2))(O-t-Bu)(7)(mu-O-t-Bu)(2) (5) and Zr(3(mu,mu'-O(2)P(O-t-Bu)(2))(5)(O-t-Bu)(7).(1)/(2)C(6)H(5)CH(3) (6.(1)/(2)C(6)H(5)CH(3)) have been isolated from the reaction of 1 with cacodylic acid and di-tert-butyl phosphate, respectively. The X-ray structures of 2, 3, 5, and 6 have been determined; although the X-ray structural analysis of 4 could not be satisfactorily finished, it reveals the disposition of the substituents. The solution state NMR data suggest that these compounds undergo structural changes in solution. Possible relationships among the various structures are discussed.     

Isolation and structural characterization of 1,5-benzodiazepinium cation in an inorganic–organic hybrid compound [C12H17N2]3[Bi2Cl9]·2EtOH

The compound [C₁₂H₁₇N₂]₃[Bi₂Cl₉]·2EtOH (1) has been synthesized from bismuth trichloride and o-phenylenediamine (opda) in ethanol at an aerial ambient condition. This preparation includes the conversion of opda to 2,3-dihydro-1H-1,5-benzodiazepinium cation through its reaction with acetone that is formed in situ from aerial ethanol oxidation. Compound 1 crystallizes in triclinic system (space group P−1). In the crystal structure of 1, the supramolecular hydrogen bonding interactions between [Bi₂C₉]³⁻ and [C₁₂H₁₇N₂]⁺ play an important role in the stabilization of cationic form of 2,3-dihydro-1H-1,5-benzodiazepine and in obtaining emission signals of the organic moiety, which is otherwise not emissive. Compound [C₁₂H₁₇N₂]₃[Bi₂Cl₉]·2(2-PrOH) (2), that has been isolated from 2-propanol (instead of ethanol), is isostructural with compound 1.     

A new synthesis of 2-substituted pyridines via aluminum chloride induced heteroarylation of arenes and heteroarenes

[reaction: see text] We herein report a new synthesis of 2-(hetero)aryl-substituted pyridines via heteroarylation of arenes/heteroarenes through AlCl(3)-induced C-C bond-forming reactions. 2-Halopyridines bearing an electron-withdrawing group were reacted with a number of (hetero)arenes to give 2-aryl/heteroaryl-substituted pyridines in good yields.