o‐Carboxybenzoylferrocene. Bioactivity and chemical Modifications

The antitumor activity of o‐carboxybenzoylferrocene sodium salt ( 1 ) was studied in vivo . Interaction between o‐carboxybenzoylferrocene ( 2 ) and N,N′‐carbonyldiimidazole in boiling methylene dichloride leads to 3‐(N‐imidazolyl)‐3‐ferrocenylisobenzofuran‐1(3H)‐one ( 5 ). The structure of compound 5 was established by X‐ray analysis. Aminolysis of compound 5 in toluene gave rise to ferrocenoylbenzamides ( 6a – d )–derivatives of dimethylamine, piperidine, pyrrolidine and morpholine. Copyright © 2008 John Wiley & Sons, Ltd.     

Highly sensitive detection of five typical fluoroquinolones in low‐fat milk by field‐enhanced sample injection‐based CE in bubble cell capillary

Fluoroquinolones are a group of synthetic antibiotics with a broad activity spectrum against mycoplasma, Gram‐positive, and Gram‐negative bacteria. Due to the extensive use of fluoroquinolones in farming and veterinary science, there is a constant need in the analytical methods able to efficiently monitor their residues in food products of animal origin, regulated by Commission Regulation (European Union) no. 37/2010. Herein, field‐enhanced sample injection for sample stacking prior the CZE separation was developed inside a bubble cell capillary for highly sensitive detection of five typical fluoroquinolones in bovine milk. Ethylenediamine was proposed as the main component of BGE for the antibiotics separation. The effect of BGE composition, injection parameters, and water plug length on the field‐enhanced sample injection‐based CE with UV detection was investigated. Under the optimized conditions, described field‐enhanced sample injection‐based CE‐UV analysis of fluoroquinolones provides LODs varying from 0.4 to 1.3 ng/mL. These LOD values are much lower (from 460 to 1500 times) than those obtained by a conventional CE in a standard capillary without bubble cell. The developed method was finally applied for the analysis of fluoroquinolones in low‐fat milk from a Swiss supermarket. Sample recovery values from 93.6 to 106.0% for different fluoroquinolones, and LODs from 0.7 to 2.5 μg/kg, were achieved. Moreover, the proposed ethylenediamine‐based BGE as volatile and compatible with MS system, enabled the coupling of the field‐enhanced sample injection‐based CE with a recently introduced electrostatic spray ionization MS via an iontophoretic fraction collection interface for qualitative fluoroquinolones identification.     

Ultrasound-assisted emulsification microextraction of organolead and organomanganese compounds from seawater, and their determination by GC-MS

We describe a simple method for the simultaneous determination of organolead and organomanganese compounds in seawater samples. It is based on ultrasound-assisted emulsification microextraction. Trimethyllead, triethyllead, tetraethyllead, cyclopentadienylmanganese tricarbonyl and its methyl derivative were separated and determined using gas chromatography and mass spectrometry. Trimethyllead and triethyllead were derivatized with sodium tetraphenylborate before being submitted to the preconcentration step. Detection limits ranged from 7.0 to 41 ng L^?1 depending on the compound. Recoveries ranged from 84 to 118 %, depending on the compound and the sample analyzed. Seawater samples were collected at different sites of the Cartagena Bay and none of the target analytes were found at levels above the corresponding detection limits.

1,2,5-Thiadiazole 2-oxides: selective synthesis,structural characterization,and electrochemical properties

A new general procedure for the selective synthesis of 1,2,5-thiadiazole 2-oxides (including fused derivatives) 8a,b,c,g,h from the reaction of vic-glyoximes with S₂Cl₂ and pyridine in acetonitrile was elaborated together with general procedure for the synthesis of 1,2,5-thiadiazoles 7a–i, 10, 12, and 14 from the same starting materials and reagents. Molecular structures of 3,4-dimethyl-1,2,5-thiadiazole 2-oxide 8a and [1,2,5]thiadiazolo[3,4-b]quinoxaline 10 were confirmed by single-crystal X-ray diffraction. Electrochemical properties of 1,2,5-thiadiazole 2-oxides 8 were studied by cyclic voltammetry and different behavior was observed for monocyclic and benzo-fused derivatives. With compounds 8g and 17, previously unknown deoxygenation of 2,1,3-benzothiadiazole 1-oxides was discovered by electrochemical reduction, and resulted 2,1,3-benzothiadiazoles 7g and 19 were detected in the forms of their radical anions by EPR spectroscopy combined with DFT calculations.     

Cascade synthesis of pyrido[3,2-a]indolizines by reaction of Kröhnke–Mukaiyama salts with malononitrile dimer

An efficient protocol for the synthesis of highly functionalized 2-aminoindolizines and pyrido[3,2-a]indolizines has been achieved via the reaction of N-RC(O)CH₂-2-chloropyridinium bromides with 2-amino-1,1,3-tricyanopropene in the presence of Et₃N. The reaction of N-allyl-2-chloropyridinium bromide with 2-amino-1,1,3-tricyanopropene in the presence of Et₃N gives 3-[1-allylpyridin-2(1Н)-ylidene]-2-aminoprop-1-ene-1,1,3-tricarbonitrile, which could be cyclized to give [2-amino-(2-amino-3-vinylindolizin-1-yl)methylene]malononitrile upon treatment with KOH–DMF.     

Design of Fluorescent Nanocapsules as Ratiometric Nanothermometers

We have developed a novel design of optical nanothermometers that can measure the surrounding temperature in the range of 20–85 °C. The nanothermometers comprise two organic fluorophores encapsulated in a crosslinked polymethacrylate nanoshell. The role of the nanocapsule shell around the fluorophores is to form a well‐defined and stable microenvironment to prevent other factors besides temperature from affecting the dyes’ fluorescence. The two fluorophores feature different temperature‐dependent emission profiles; a fluorophore with relatively insensitive fluorescence (rhodamine 640) serves as a reference whereas a sensitive fluorophore (indocyanine green) serves as a sensor. The sensitivity of the nanothermometers depends on the type of nanocapsule‐forming lipid and is affected by the phase transition temperature. Both the fluorescence intensity and the fluorescence lifetime can be utilized to measure the temperature.     

Thermal properties of mixed-ligand magnesium complexes with beta-diketonates and diamimes as potential MOCVD precursors

The series of adducts of magnesium beta-diketonates with diamimes namely Mg(thd)₂(tmeda) 1 and four new complexes Mg(thd)₂(tmpda) 2, Mg(thd)₂(pda) 3, Mg(ptac)₂(tmeda) 4, Mg(tfac)₂(tmeda) 5 [beta-diketonates = R₁C(O)CHC(O)R₂: thd (R₁ = R₂ =  ^t Bu), ptac (R₁ =  ^t Bu, R₂ = CF₃), tfac (R₁ = Me, R₂ = CF₃); diamines = R₂N(CH₂) _n NR₂: tmeda (n = 2, R = Me), tmpda (n = 3, R = Me), pda (n = 3, R = H)] were synthesized in order to investigate the influence of both ligand types on the thermochemical properties of these compounds. The thermal behavior of the complexes in the condensed phase was investigated by thermogravimetry and differential scanning calorimetry; the thermodynamic parameters of phase transitions were determined. The saturated vapor pressure of solid complexes Mg(thd)₂(tmeda) and Mg(tfac)₂(tmeda) were measured by the transmission method giving the enthalpies and entropies of sublimation processes. The reliable thermodynamic data for compound Mg(thd)₂(tmeda) were obtained with the assistance of X-ray diffraction and the static method of saturated and unsaturated vapor pressure measurements.