MALDI-TOF Mass Spectrometry of Nanosized MoO<Subscript>2</Subscript>. Structure and Relative Stability of Isomers of Lower Molybdenum Oxide Cations

MALDI-TOF was used to study molybdenum dioxide (MoO₂) containing a nanosized fraction. The composition of cationic clusters of nonstoichiometric lower molybdenum oxides in the gas phase was determined, and the thermodynamic stabilities and configurations of isomers were calculated for selected symmetric molecular structures and for cations MoSO ₈ ⁺ and Mo₅O ₉ ⁺ . Molecular orbital analysis was performed for two trigonal-bipyramidal clusters Mo₅O₈ and Mo₅O₉. Changes in molybdenum–molybdenum interatomic distances in going from MoO ₈ ⁺ and Mo₅O ₉ ⁺ cations to neutral clusters are discussed.     

Modification of solitary waves by third-harmonic generation

The effect of phase-matched third-harmonic generation on the structure and stability of spatial solitary waves is investigated. A power threshold for the existence of two-frequency spatial solitons is found, and the multistability of solitary waves in a Kerr medium owing to a higher-order nonlinear phase shift caused by cascaded third-order processes is revealed.     

Pattern-based sensing of nucleotides in aqueous solution with a multicomponent indicator displacement assay

A multicomponent indicator displacement assay (MIDA) based on an organometallic receptor and three dyes can be used for the identification and quantification of nucleotides in aqueous solution at neutral pH.     

Synthesis of polyaza macrocycles by palladium-catalyzed amination of 1,2-dibromobenzene and 2-bromo-1,3-dichlorobenzene

Palladium-catalyzed amination of 1,2-dibromobenzene with equimolar amounts of linear polyamines leads to the formation of polyaza macrocycles in low yields. The use of 2-bromo-1,3-dichlorobenzene as starting compound ensures considerably larger yields of the target macrocycles, and the reaction is accompanied by side formation of N-aryl- and N,N′-diaryl-substituted polyamines, as well as of cyclic oligomers. The yields strongly depend on the polyamine chain length. Reactions of excess 2-bromo-1,3-dichlorobenzene with a series of polyamines gave the corresponding N,N′-diarylpolyamines in high yields, and the latter reacted with the second polyamine molecule to form cyclic dimers. A relation between the yield of cyclic dimers and polyamine structure was revealed.     

Palladium-catalyzed amination in the synthesis and modification of acyclic oxadiamino cholane derivatives

Palladium-catalyzed reactions of 24-(haloaryloxy)cholanes and 3,24-bis(haloaryloxy)cholanes with excess oxadiamines gave the corresponding mono- and bis(oxadiamino)-substituted cholanes which were subjected to palladium-catalyzed arylation with 1,3-dibromobenzene, 2,6-dibromopyridine, 1,8-dichloroanthracene, 9-bromoanthracene, 1-chloroanthracene, and 1-chloroanthraquinone. The results of these reactions were found to strongly depend on the haloarene nature. The arylation with 1,3-dibromobenzene and 2,6-dibromopyridine led to the formation of new macrocyclic compounds containing one cholane, one arene, and two oxadiamine fragments.     

Calculation of heat adsorption of certain halomethanes on graphitized thermal black

Initial heats of adsorption of a number of halomethanes on graphite have been calculated by a semiempirical molecular-statistical method and from the proportionality of the heat of adsorption to critical parameters of the adsorbate. The results from these calculations are in satisfactory agreement with each other and with the available experimental data.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1721–1723, August, 1989.     

Adsorption Properties of Thiocontaining Schungite

Chromatography–mass spectrometry and thermodesorption mass spectrometry have been employed to study mineral schungite-III, in which various thiocompounds have been detected and identified. The influence of these compounds on the adsorption activity of schungite with respect to iodine has been investigated. It has been shown that sulfur present in schungite has no effect on the results of determining its adsorption activity and does not interact with iodine; however, it can interact with amino compounds to yield sulfides. Activation energies E_a have been experimentally determined for sulfur, iodine, and dimethyl disulfide desorption from the surfaces of schungite and a model sorbent, graphitized thermal carbon black. The E_a values of these compounds have appeared to be several times lower than the heats of their adsorption on carbon black calculated by the molecular-statistical method.     

Special Features of the Interaction between Asymmetric Dimethylhydrazine and Thiocontaining Schungite

The interaction between asymmetric dimethylhydrazine and thiocontaining mineral schungite-III has been studied. Chromatography–mass spectrometry has been used to identify alkyl polysulfides as the products of desorption of asymmetric dimethylhydrazine from schungite surface. The interaction of asymmetric dimethylhydrazine with crystalline sulfur has been investigated in a model system. Dimethyl polysulfides, CH₃S_nCH₃; (dimethylamino)methyl polysulfides, (CH₃)₂NS_nCH₃; and bis(dimethylamino) polysulfides, (CH₃)₂NS_nN(CH₃)₂, with 2 ≤ n ≤ 4 have been detected. Gas-chromatographic retention indices have been determined for the products of the interaction of asymmetric dimethylhydrazine with sulfur and the schungite material.