Hybrid silica-organic material with immobilized amino groups: surface probing and use for electrochemical determination of nitrite ions

A sol–gel based hybrid process was developed by manipulating different techniques in sol–gel process to synthesize γ-alumina and (CuO, CuO + ZnO) doped γ-alumina spherical particles. Catalysts having spherical geometry have an important advantage over powders or pellets which are impervious to fluids, when packed in a reactor. Boehmite sol was used as alumina precursor for synthesizing porous γ-alumina and doped materials. γ-alumina particles having 5 wt% CuO, 4 wt% CuO + 1 wt% ZnO, 3 wt% CuO + 2 wt% ZnO and 2 wt% CuO + 3 wt% ZnO were prepared by adding required amounts of Cu(NO₃)₂ and Zn(NO₃)₂ solutions prior to gelation of the sol. Methanol dehydration studies were carried out by employing these synthesized catalysts. Hundred percent conversion of methanol to dimethyl ether was observed with (4 wt% CuO + 1 wt% ZnO)-γ-alumina and (5 wt% CuO)-γ-alumina microspheres at 325 and 350 °C, respectively.     

Statistics of the Popularity of Chemical Compounds in Relation to the Non-Target Analysis

The idea of popularity/abundance of chemical compounds is widely used in non-target chemical analysis involving environmental studies. To have a clear quantitative basis for this idea, frequency distributions of chemical compounds over indicators of their popularity/abundance are obtained and discussed. Popularity indicators are the number of information sources, the number of chemical vendors, counts of data records, and other variables assessed from two large databases, namely ChemSpider and PubChem. Distributions are approximated by power functions, special cases of Zipf distributions, which are characteristic of the results of human/social activity. Relatively small group of the most popular compounds has been denoted, conventionally accounting for a few percent (several million) of compounds. These compounds are most often explored in scientific research and are practically used. Accordingly, popular compounds have been taken into account as first analyte candidates for identification in non-target analysis.     

Ferromagnetically Coupled S=1 Chains in Crystals of Verdazyl-Nitronyl Nitroxide Diradicals

Thermally stable organic diradicals with a triplet ground state along with large singlet-triplet energy gap have significant potential for advanced technological applications. A series of phenylene-bridged diradicals with oxoverdazyl and nitronyl nitroxide units were synthesized via a palladium-catalyzed cross-coupling reaction of iodoverdazyls with a nitronyl nitroxide-2-ide gold(I) complex with high yields. The diradicals exhibit high stability and do not decompose in an inert atmosphere up to 180 °C. For the diradicals, both substantial AF (ΔE_ST≈−64 cm⁻¹) and FM (ΔE_ST≥25 and 100 cm⁻¹) intramolecular exchange interactions were observed. The sign of the exchange interaction is determined both by the bridging moiety (para- or meta-phenylene) and by the type of oxoverdazyl block (C-linked or N-linked). Upon crystallization, diradicals with the triplet ground state form unique one-dimensional exchange-coupled chains with strong intra- and weak inter-diradical ferromagnetic coupling.     

Synthesis,antiradical, and antimicrobial activities of new pteridine-2,4,7-trione derivatives

The synthesis of 6-(2-hydroxy-2-aryl (heteryl)ethyl)-1-methylpteridine-2,4,7(1H,3H,8H)-triones by the reduction of the corresponding ketones and the peculiarities of conversion of the synthesized alcohols to (E)-1-methyl-6-(2-aryl (heteryl)ethenyl)pteridine-2,4,7(1H,3H,8H)-triones was reported. The mechanism of monomolecular elimination that occurred in the presence of hydrogen halides was discussed, namely, the competitive formation of an energy-efficient conjugated system by deprotonation of a stable benzyl-type carbocation. Alternative synthesis methods of pteridine-2,4,7(1H,3H,8H)-triones were developed. Abovementioned approach involved [4+2]-cyclocondensation of 1-methyl-5,6-diaminouracil to 2-oxo-4-R-but-3-enoic acids and Knoevenagel condensation of 1,6-dimethylpteridine-2,4,7(1H,3H,8H)-trione with aromatic aldehydes. The antiradical, antimicrobial, and antifungal activities were studied for the synthesized compounds.     

Preparation and characterization of octadecylsilane monolayers on indium–tin oxide (ITO) surfaces

The preparation and characterization of octadecylsilane, C₁₈, monolayers on indium–tin oxide (ITO) have been studied carefully. A reproducible procedure was developed for the formation of C₁₈/ITO employing octadecyltrimethoxysilane (OTMS) as a monomer. The films were studied by means of electrochemistry, wettability, infrared and atomic force microscopy. All these measurements provide evidence for the formation of a disorganized, ‘brush-type’ monolayer with a maximum surface fractional coverage of 0.90±0.04. The surface coverage can be controlled through the silanization time. The applications and implications of such disorganized monolayers in electroanalytical chemistry are discussed.