Synthesis, structure, and magnetic properties of 2,2′-(buta-1,3-diyne-1,4-diyl)bis(4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole 3-oxide 1-oxyl)

An approach to the synthesis of nitronyl nitroxide 2,2′-(buta-1,3-diyne-1,4-diyl)bis(4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole 3-oxide 1-oxyl) (4) was developed. Compound 4 is the first diradical with nitronyl nitroxide groups directly linked through a diacetylene fragment. In solid phase the diradicals are arranged in stacks with parallel CC fragments, with the distances between the terminal carbon atoms of the neighboring diacetylene groups (T and d) being 6.170 and 4.466 Å, respectively, and the angle between the translation vector and the median line passing through the CCCC fragment of 45.9°. The values of T and d are outside the range of structural criteria allowing a topochemical reaction. Thus UV irradiation does not initiate solid phase polymerization of 4. After exposure at 373 K for 1 h the crystals of 4 turn dark-brown, become X-ray amorphous and lose the majority of their paramagnetic centers without significantly changing their mass. Upon further heating up to 400-420 K the product explodes, releasing about 360 kJ/mol of heat. A diluted solution of 4 in 1,4-dioxane produces an EPR spectrum typical of a strong exchange (a multiplet of nine broadened lines with A_4N = 0.35 mT), indicating the efficiency of the CCCC fragment as an exchange channel. The character of the experimental μ_eff(T) dependence for 4 indicates a strong intramolecular antiferromagnetic-type exchange interaction (J/k_B ∼ −104 K) and the dominating weak intermolecular ferromagnetic exchange.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-(phosphonomethyl)glycine derivatives and studies of their immunotropic activity

The Petasis reaction between glyoxylic acid, α-amino phosphonates, and organylboronic acid afforded N-phosphonomethyl-α-amino acids. This method has an advantage of preparative simplicity and high diastereoselectivity of the reactions. Immunotropic activity of the synthesized compounds was studied using the models in vivo.     

Development and Comparative Study of Different Immunoenzyme Techniques for Pesticides Detection

Abstract

Different ELISA techniques have been developed for the detemination of four widely used pesticides: 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), simazine and atrazine. Dependences between the assay scheme and the limiting detectable concentration of the pesticide were studied. The cases of preferential applying of the scheme with immobilized antibodies or one with immobilized pesticide-protein conjugate have been revealed. The following approaches resulting in lowering of ELISA sensitivity were proposed: preliminary incubation of the tested sample with antibodies, immobilization of antibodies via staphylococcal protein A, usage of monovalent fragments of antibodies instead of native ones and chemical modification of the pesticide molecules in the sample. Optimal combinations of these approaches permitted to lower the detection limit of the assays in about 5–30 times. The achieved sensitivities were 3 ng/mL for 2,4-D, 5 ng/mL for 2,4,5-T, 0.05 ng/mL for simazine, and 0.1 ng/mL for atrazine, being acceptable for purposes of ecological monitoring.     

Linear and Nonlinear Effects in Structures Based on Magnonic Crystals and Semiconductors

JETP Letters - Spin wave propagation in a magnonic crystal–semiconductor heterostructure has been theoretically studied. It has been shown that direct current in a semiconductor allows...     

Synthesis of 4<Emphasis Type="Italic">H</Emphasis>-imidazole-5-carbaldoxime 3-oxides and 4<Emphasis Type="Italic">H</Emphasis>-imidazole-5-carbonitrile 3-oxides

The condensation of 3-hydroxyamino-3-methylbutan-2-one or 3-ethyl-3-hydroxyamino-pentan-2-one with aldehydes and ammonia afforded a series of new 1-hydroxy-4-methyl-2,5-dihydroimidazoles, whose oxidation gave rise to the corresponding 5-methyl-4H-imidazole 3-oxides. The latter, like 1-hydroxy-4-methyl-2,5-dihydroimidazoles, react with PrⁱONO in the presence of bases to form 4H-imidazole-5-carbaldoxime 3-oxides, which are transformed into 4H-imidazole-5-carbonitrile 3-oxides in the reaction with TsCl in the presence of Et₃N. The by-products produced in different steps of the synthesis were isolated and characterized. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1487–1503, July, 2008.     

129Xe nuclear magnetic resonance study of pitch-based activated carbon modified by air oxidation/pyrolysis cycles: a new approach to probe the micropore size

(129)Xe NMR has been used to study a series of homologous activated carbons obtained from a KOH-activated pitch-based carbon molecular sieve modified by air oxidation/pyrolysis cycles. A clear correlation between the pore size of microporous carbons and the (129)Xe NMR of adsorbed xenon is proposed for the first time. The virial coefficient delta(Xe)(-)(Xe) arising from binary xenon collisions varied linearly with the micropore size and appeared to be a better probe of the microporosity than the chemical shift extrapolated to zero pressure. This correlation was explained by the fact that the xenon collision frequency increases with increasing micropore size. The chemical shift has been shown to vary very little with temperature (less than 9 ppm) for xenon trapped inside narrow and wide micropores. This is indicative of a smooth xenon-surface interaction potential.     

Stereoisomeric complexes of Pt(II) with threonine and allothreonine

The paper describes the synthesis of geometrical isomers and diastereomers of Pt(II) bischelates with diastereomeric hydroxy-amino acids threonine (threo-α-amino-β-hydroxybutyric acid CH₃C*H(OH)C*H(NH₂)COOH=ThrH) and allothreonine (erythro-α-amino-β-hydroxybutyric acid=alloThrH) containing two asymmetric carbon atoms C*: cis-,trans-[Pt(S-Thr)₂], cis-,trans-[Pt(RThr)(S-Thr)], cis-,trans-[Pt(R-alloThr)(S-alloThr)] (where R and S are the absolute configurations of the asymmetric carbon atom bonded to the carboxyl group). ¹⁹⁵Pt NMR spectroscopy is used to investigate the successive phases of the synthesis of the stereoisomeric Pt(II) complexes with threonine. The synthesized complexes are studied by ¹H, ¹³C, ¹⁹⁵Pt NMR spectroscopy, IR spectroscopy, and single crystal XRD.     

Silyl- and germylpropynals in the synthesis of azolyl-substituted 2-imidazoline 3-oxide 1-oxyls

Azolyl-substituted nitronylnitroxyls were synthesized using Me 3Si- and Et 3Ge-substituted propynals. When synthesizing 2-[3-(triethylgermyl)-l H-pyrazol-4-yl]-4,4,5,5-tetramethyl-4,5-dihydro-1 H-imidazole 3-oxide 1-oxyl ( 3b), the cycle was assembled by the reaction of CH2N2 with the corresponding triethylgermylethynyl-substituted nitronylnitroxyl. In the case of 2-[4-(trimethylsilyl)-l H-1,2,3-triazol-5yl]- (8a) and 2-[4-(triethylgermyl)-1 H-1,2,3-triazol-5-yl]-4,4,5,5-tetramethyl-4,5-dihydro-l H-imidazole 3-oxide l-oxyls (8b), the corresponding heterocyclic aldehydes were synthesized first and then were used for the preparation of compounds 8a and 8b. According to the X-ray diffraction study, the presence of the bulky substituent Me3Si or Et3Ge in the heterocycle causes its turn by 40.9(2)° in 8a and 33.6(6)° in 3b relative to the plane of the paramagnetic fragment ONCNO.