RESUMO

In the title compounds, 3-(dihydroxyboryl)anilinium bisulfate monohydrate, C6H9BNO2+·HSO4-·H2O (I), and 3-(dihydroxyboryl)anilinium methyl sulfate, C6H9BNO2+·CH3SO4- (II), the almost planar boronic acid molecules are linked by pairs of O-H...O hydrogen bonds, forming centrosymmetric motifs that can be described by the graph-set R22(8) motif. In both crystals, the B(OH)2 group acquires a syn-anti conformation (with respect to the H atoms). The presence of the hydrogen-bonding functional groups B(OH)2, NH3+, HSO4-, CH3SO4- and H2O generates three-dimensional hydrogen-bonded networks, in which the bisulfate (HSO4-) and methyl sulfate (CH3SO4-) counter-ions act as the central building blocks within the crystal structures. Furthermore, in both structures, the packing is stabilized by weak boron-π interactions, as shown by noncovalent interactions (NCI) index calculations.

RESUMO

Fluorescent nitrogen-doped graphene oxide dots (NGODs) have been demonstrated as an on-off nanosensor for the detection of Hg2+, Au3+, and H2O2. As compared to l-cystine, where the luminescence signal recovery results from the detachment of Hg2+ from the NGODs, signal recovery through l-ascorbic acid (turn-off-on model) has been attributed to the reduction of Hg2+ to Hg0. The sustainable recovery of the photoluminescence signal is demonstrated using common citrus fruits containing vitamin C (l-AA), suggesting a promising practical usage of this sensing system. Additionally, the sensitivity of NGOD- and AA-originated signal recovery from the Hg(II)-NGODs mixture has been successfully tested in Hg2+ ion-spiked tap water from three different places. Mimic devices were executed and verified on the basis of characteristic spectral changes, and the possible utility of this system in electronic security and memory element devices has also been demonstrated. Considering an easy synthesis process and excellent performance of NGODs, this investigation opens up new opportunities for preparing high-quality fluorescent NGODs to meet the requirements of many applications.

RESUMO

The aim of this study was to assess the changes in the characteristics of rheumatoid arthritis information on the Internet over a 15-year period and the positioning of Web sites posted by universities, hospitals, and medical associations. We replicated the methods of a 2001 study assessing rheumatoid arthritis information on the Internet using WebCrawler. All Web sites and pages were critically assessed for relevance, scope, authorship, type of publication, and financial objectives. Differences between studies were considered significant if 95 % confidence intervals did not overlap. Additionally, we added a Google search with assessments of the quality of content of web pages and of the Web sites posted by medical institutions. There were significant differences between the present study's WebCrawler search and the 2001-referent study. There were increases in information sites (82 vs 36 %) and rheumatoid arthritis-specific discussion pages (59 vs 8 %), and decreases in advertisements (2 vs 48 %) and alternative therapies (27 vs 45 %). The quality of content of web pages is still dispersed; just 37 % were rated as good. Among the first 300 hits, 30 (10 %) were posted by medical institutions, 17 of them in the USA. Regarding readability, 7 % of these 30 web pages required 6 years, 27 % required 7-9 years, 27 % required 10-12 years, and 40 % required 12 or more years of schooling. The Internet has evolved in the last 15 years. Medical institutions are also better positioned. However, there are still areas for improvement, such as the quality of the content, leadership of medical institutions, and readability of information.

Assuntos

RESUMO

In the title compound, C33H38N2O2, each of the cyclo-hexyl rings adopts a chair conformation. The two planes involving carbonyl groups, C-(C=O)-N and N-(C=O)-N, are oriented at a dihedral angle of 62.28 (10)°. In the crystal, two neighboring mol-ecules are linked by a pair of N-H⋯O inter-actions, generating an inversion dimer. The dimers are inter-connected by C-H⋯O hydrogen bonds into a supra-molecular chain along the a-axis direction.

RESUMO

Thermal and microwave reactions between [PcSn(IV)Cl2] (1) and the potassium salts of eight fatty acids (2 a-h) led to cis-[(RCO2)2Sn(IV)Pc] compounds (3 a-h) in yields ranging from 54 to 90 %. Compounds 3 a-h were fully characterized by elemental analysis, spectroscopy (IR, UV/Vis, multinuclear NMR), and seven X-ray diffraction structures, whereby two different allotropes were observed in two cases. The two carboxylates in 3 have a cis anisobidentate binding mode, octacoordination of the tin atoms with square-antiprismatic geometry, and pi-electron-rich nanocap shapes. On account of the latter characteristics, 3 a-h compounds have anticorrosion properties. LPR and Tafel electrochemical methods were used to characterize the behavior of these derivatives in naturally aerated sour brine, which is a common environment in petroleum production and refinery operations. The measurement of the corrosion rate of carbon steel AISI 1018 in the presence of 3 a-h (500 ppm) gave efficiencies of 61-87 % for the inhibitor performance. Of the different derivatives examined, compounds 3 e and 3 h were the most effective corrosion inhibitor prototypes.

RESUMO

The simple condensation reaction of 3,5-di-tert-butyl salicylaldehyde and 3-aminophenylboronic acid leads to a trimeric macrocyclic compound. The ability of this molecule to include small organic molecules was in a first approximation analyzed by (1)H NMR spectroscopy and X-ray crystallography.

RESUMO

Two PcSn(IV) dicarboxylate molecules were obtained through efficient microwave methodology with the aim to test them as corrosion inhibitors in the oil industry. The compounds were characterized by elemental analysis, IR, UV-vis, (1)H, (13)C NMR, and X-ray diffraction. The relative configuration of the two carboxylates is cis, placing the fatty acid moieties on the same face of the phthalocyanine macrocycle. In the solid-state the tin atoms possess square antiprismatic octacoordinated geometries. Both tin phthalocyanines were tested as corrosion inhibitors for hydrogen sulfide corrosive media showing a chemisorption process of the nanocap motifs on the metallic surface. Apparently, the length of the hydrophobic chain contributes significantly to the inhibition efficiency, in the sense that shorter chains increase the efficiency.