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C25H31F3N4OS, monoclinic, P21/c (no. 14), a = 6.7323(1) Å, b = 15.4999(2) Å, c = 23.7905(4) Å, β = 93.037(2)°, V = 2479.05(6) Å3, Z = 4, R gt(F) = 0.0473, wR ref(F 2) = 0.1394, T = 293 K.

C20H30N4O3S, orthorhombic, P212121 (no. 19), a = 7.7152(3) Å, b = 10.6132(2) Å, c = 25.5990(7) Å, V = 2096.12(11) Å3, Z = 4, R gt(F) = 0.0579, wR ref(F 2) = 0.1216, T = 293 K.

The subject of this paper was the study of antimicrobial capacity of silver loaded on the low temperature activated alumina products and evaluation of these products as decontaminants in the water and waste waters decontamination treatments. The low temperature activated alumina products have been characterized as valuable adsorbents in previous papers. So, by reason the next step to investigate these silver loaded products and finding their performaces as antimicrobial agents was an alluring prospect. For this purpose, a common bacterian inoculus was choosen for experiments, and a penmisive method to measure the rate of inhibition was adopted. Experimental data have shown the dependence of the inhibition rate on the following parameters concerning the adsorbent properties: the thermal treatments, particle size dimension of adsorbent (low temperature activated alumina products), concentration of siver adsorbed on particle surface and density of bioreactive centers, representing the number of particles on unit volume of the liquid containing the bacterial cells. Also, the experiments lay out that the aluminum hydroxide calcined at 300 and 400ºC exibits the largest silver adsorbed concentration and the highest inhibition rate (close to 100 %). Little dependence of inhibition rate on pH, in the interval 5.0 � 8.0, was observed. For application of depolluting agent in diferent technological processes, it is necesary to measure the minimum inhibitory concentration in therms of g of silver loaded on the low temperature activated alumina /L.

Aluminum hydroxide is a key product for the industrial production of alumiana and aluminium, ceramics insulator and refractories, desiccants, absorbents, flame retardants, filers for plastics and rubbers, catalysts, and various construction materials. The production of these arrays of useful material products is grounded on the multiple thermal decomposition pathways of Al(OH)3, which involve major crystallographic dislocations and many microstructure reconfigurations on variable lines of phase transitions, from the raw material up to large varieties of precursors and commercial grade products. A wide range of literature on this subject is available, and recent reviews cover suitable information about preparation and characterization of different activated alumina products with specific properties and applications. In our previous papers, there was studied the mechanisms of aluminum hydroxide phase transitions, during low temperature calcination, namely, at 260ºC, 300ºC, 400ºC and 600 ºC, under chosen particularly conditions, for promoting the nucleation of the amorphous phases. Collected data suggest that raw aluminum hydroxide; dried, milled and classified is a precursor for the new low temperature activated alumina transition phases, carrying distinctive characteristics and properties, due to products enrichment in amorphous phases. Accordingly, as effects of the main driving factors (temperature and rate of heating, and initial particle size dimension) on the aluminum hydroxide as new precursor, notable changes were observed in products mineral composition, morphology and specific surface area, pore size, pore distribution, and the particle size distribution. Beside, some other secondary effects have to be apprehended. For example, the main phase transition process dinamic factors control over some physical and technical properties of the new products, like: absolute density, brightness, oil absorption capacity and water absorption capacity. The purpose of this work was to continue the characterization of low temperature activation alumina products, and also, to measure the adsorption capacity and to reveal adsorption kinetics mechanisms. Thus, the first step of survey was silver adsorption maximum capacity measurements for all sample prepared by heating the precursor alumina hydroxide, milled and classified as 5 different dimension size fractions to 260, 300, 400 and 600ºC. Hereinafter, four samples, carefully selected as representative for the entire lot of samples, were used for the study of kinetics mechanism and data fitting to the adequate kinetic equations. Confident data validate the pseudo second order kinetic model for the entire activation process, independently of samples heating temperature and particles dimension.

Complex vanadates of tantalum(V), such as ATa2V2O11 (A = Sr, Pb), are rare and underrated materials, which have potential application domains that could be substantially expanded, mitigating the existing controversy on their atomic and electronic organization. Herein, we present a thorough structural examination combining synchrotron powder X-ray diffraction-aided distortion mode analysis with computational methods to study hettotypes of SrTa2V2O11 (STVO) and PbTa2V2O11 (PTVO). Being distinct from the perovskite family due to the presence of [VO4] groups, both compounds are polar dielectric materials with certain similarities to SBT and PBT Aurivillius phases. Applying the model of anions of metallic matrices to the analysis of electron localization functions calculated on top of as-established equilibrium structures helps retrace the effects in the Sr and Pb surroundings on the respective crystal packings of STVO and PTVO., Use of the Advanced Photon Source at Argonne National Laboratory was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. This research was supported by Spanish MCIU and MINECO through the following projects: PGC2018-094814-B-C2, MCI-21- PID2020-113558RB-C41, and RED2018-102612-T, and Principado de Asturias FICYT Agency (Spain) and EU-FEDER through projects FC-GRUPIN-IDI/2018/000170, FC-GRUPIN-IDI/2018/000177, SV-PA-21-AYUD/2021/51036, and SV-PA-21-AYUD/2021/50997. The authors thank the Institute for Scientific and Technological Resources and the MALTA-Consolider supercomputing center at the University of Oviedo for the technical support and primarily data acquisition

C20H24N4O2S, monoclinic, C2/c (no. 15), a = 28.5901(10) Å, b = 6.4383(4) Å, c = 20.060(1) Å, β = 99.682(4)°, V = 3639.9(3) Å3, Z = 8, R gt(F) = 0.0557, wR ref (F 2) = 0.1514, T = 150 K., Princess Nourah bint Abdulrahman University Researchers Supporting Project No. PNURSP2022R3, Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.

The slow solvent evaporation approach was used to create a single crystal of (C

In this study, four new piperazinium salts, namely, 4-phenyl-piperazin-1-ium 4-eth-oxy-benzoate monohydrate, C

This paper is reporting the data concerning impurities occlusion in the dried, milled and classified aluminum hydroxide, the sources of contamination and the ways to control the purity of classified aluminum hydroxide as raw material for special aluminas. Mainly, all the micronic size particles, floating in the super-saturated Bayer liquors, are potential sources of occluded impurities in the aluminum hydroxide particles. There are several mechanisms for embedding the impurities in crystalline substances. Of these, most probable ones in the Bayer alumina process are: a) occlusion of the spent liquor drops containing impurities inside the polycrystalline aluminum hydroxide congregates; b) hetero-nucleation of aluminum hydroxide on the surface of particles or colloids containing one or more impurities (the foreign particles are seized inside a crystals or inside of a crystalline multi-particulate association); c) incorporation of available ions or molecule reactive fragments in the poor crystalline structures of aluminum hydroxide after nucleation, during different growth stages of all already aggregated particles, under certain super-saturations. d) building up bridges between the scanty aggregated particles or filling the inside hollows of these aggregates with new quickly crystallized material, including the particulate impurities, mainly, during large fluctuations of the super-saturation. Using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy EDS (Apollo SSD detector, EDAX), the contributions of each of these mechanisms can be investigated simply and assumed from the collected data. It was shown that well crystallized phases originating directly from bauxite (like the aluminum substituted goethite and substituted hematite, rutile or quartz), as well as the well as the crystallized new born phases during specific Bayer reactions (like cancrinite, are not promoting directly the impurities occlusion. Poor crystalline phases (like sodalite and katoite or other secondary phases and their micronic size fragments are really sustaining impurities occlusion through all the acknowledged mechanisms.

The syntheses and crystal structures of two novel adamantane-substituted N-Mannich bases are reported herein. In the crystals of both compounds, there are C—H⋯F hydrogen bonds present, forming inversion dimers in one and chains in the other., In the title N-Mannich bases, 3-(adamantan-1-yl)-4-(4-fluoro­phen­yl)-1-[(4-phenyl­piperazin-1-yl)meth­yl]-4,5-di­hydro-1H-1,2,4-triazole-5-thione (C29H34FN5S) (I), and 3-(adamantan-1-yl)-4-(4-fluoro­phen­yl)-1-{[4-(2-meth­oxyphen­yl)piperazin-1-yl]-meth­yl}-4,5-di­hydro-1H-1,2,4-triazole-5-thione (C30H36FN5OS) (II), fluoro­phenyl, adamantane and piperazine moieties are linked to a planar triazole ring. There is an additional phenyl ring on the piperazine ring in (I) and a meth­oxy­phenyl ring in (II). In compound (I), the fluoro­phenyl and phenyl rings are inclined to the triazole ring by 86.55 (13) and 60.52 (12)°, respectively, and the two aryl rings are inclined to one another by 66.37 (13)°. In compound (II), the corresponding dihedral angles are 83.35 (13), 71.38 (15) and 11.97 (16)°, respectively. The crystal structure of (I) shows pairs of C—H⋯F hydrogen bonds forming inversion dimers, while in the crystal of compound (II), in addition to the C—H⋯F hydrogen bonds that generate chains parallel to the b axis, there are C—H⋯π inter­actions present that link the chains to form layers parallel to the ab plane.

Acetonides 1, easily obtained from simple terpenes, react with bispyridine iodonium (I) tetrafluoroborate (Ipy(2)BF(4)) and tetrafluoroboric acid in the presence of nucleophiles to give the corresponding adducts 2 with complete regio and diastereofacial control. Acetonides 1 containing a properly located phenyl or benzyloxy group easily undergo iodocyclization to furnish compounds 3 and 4.

A study of the protonation of the cycloadducts derived from the dearomatization reaction of lithiated N-alkyl-N-benzyldiphenylphosphinamides has been carried out. The regio- and stereoselectivity of the process has been analyzed in terms of the size of the N-alkyl substituent, the acidity and size of the protonating reagent, and the cosolvent used. The optimization of these variables allowed the preparation of tetrahydrobenzo[c]-1-aza-2λ5-phospholes containing a 1,3-cyclohexadiene or 1,4-cyclohexadiene system with moderate to excellent regio- and stereocontrol. The heterocycles were readily hydrolyzed, affording γ-(N-alkylamino)diphenylphosphinic acids with the functionalities linked to a cyclohexadiene substructure.

The proton form of the exchanger Na{sub 2}Ti{sub 2}O{sub 3}(SiO{sub 4}){center_dot}2H{sub 2}O exhibits a high selectivity for Cs{sup +} even in acid solutions. A neutron diffraction study was carried out to locate the position of the exchangeable protons. The structure contains cubane-like Ti{sub 4}O{sub 4} clusters bridged by silicate groups. The acidic proton is located on the cubane oxygens which make them four-coordinate, being bonded to three titaniums and one proton. The unit cell is tetragonal. There are six water molecules per tunnel and two tunnels per unit cell. Thus, the empirical formula is Ti{sub 2}(OH){sub 2}OSiO{sub 4}{center_dot}1.5H{sub 2}O. The water molecules are H-bonded to the framework oxygens and to each other. Although the tunnels are filled with water molecules, framework sites normally occupied by Na{sup +} are empty. The high selectivity for Cs{sup +} apparently stems from the ability to form a thermodynamically stable eight-coordinate complex by replacement of the hydroxyl protons.

Enantiomerically pure orthogonally N,N′-diprotected azaprolines 1 and 2,4-diaminoalcohols 2 are readily accessible by [3+2] cycloaddition of (−)-8-phenylmenthol-derived alkenyl Fischer carbene complexes 3 with diazomethane derivatives.

Formation of polycyclic structures within a few minutes: The intramolecular cyclization of diynes, activated by a benzenesulfenyl substituent, upon reaction with IPy2 BF4 proceeds as an efficient exo-endo coupling. A subsequent novel Friedel-Crafts-like ring closure provides the product [Eq. (1)]. Thus, intra- and intermolecular cyclizations can be carried out.

A new type of cyclic amino-functionalized s-cis boroxyvinylcarbene complex of group 6 metals has been synthesized. These complexes underwent Diels−Alder-type reactions with 2-amino 1,3-dienes that proceeded with complete regioselectivity and high exo or endo diastereoselectivity, which was found to be highly dependent on the nature of the substituents on the diene. When chiral 2-amino-5-alkoxy dienes derived from (S)-prolinol benzyl or methyl ether were used, an exclusive exo and highly diastereofacially selective [4 + 2] cycloaddition was achieved, affording spiro carbene complexes with three contiguous stereogenic centers and a high level of enantiomeric purity. Removal of the Cr(CO)5 fragment and the BF2 group provided an entry to α,α-branched β-amino aldehydes or β-amino acids. In addition, the stable form of an amino-substituted hydroxycarbene complex of chromium was characterized by X-ray diffraction.

Title compounds with x = 0.00, 0.34, 0.59, 0.70, and 1.00 are prepared by hydrothermal reaction of MCl2 (M: Ni, Co) and solid (NH2)2CO in aqueous H3PO4 (autoclave, 180 °C, 7 d).

The intentional introduction of transition metal impurities into semiconductor nanocrystals is an attractive approach for tuning quantum dot photoluminescence emission. Particularly, doping of ZnS quantum dots with Mn(2+) (Mn:ZnS QDs) results in a phosphorescence-type emission, attributed to the incorporation of manganese ions into the nanocrystal structure, so that delayed radiational deactivation of the energy of nanoparticles, excited through the energy levels of the metal, is enabled. However, the development of effective doping strategies can be challenging, especially if a highly efficient photoluminescent emission within a known crystalline core structure, is required (e.g. for analytical phosphorescence applications). The spectroscopic properties and the crystal structure of Mn(2+)-doped ZnS QDs are studied here to provide a better understanding on how the luminescence emission and the crystalline composition are influenced by the presence of Mn(2+) and its concentration used during the synthesis. In order to further control and optimize the synthesis of doped QDs for future bioanalytical applications, different complementary techniques including photoluminescence and X-ray powder diffraction have been employed. The information obtained has allowed standardization of the synthesis conditions of these doped QDs and the identification and quantification of the crystal phases obtained under different synthesis conditions.

Michael addition reactions of ketone and ester lithium enolates to optically active Fischer vinylcarbene complexes derived from (-)-8-phenylmenthol take place with high syn selectivity and high levels of asymmetric induction. The initial Michael adducts can be further elaborated through diastereoselective addition of organometallic reagents to ketones and aldol reactions. Removal of the metal fragment and chiral auxiliary group leads to cyclic enol ethers with three or five contiguous stereogenic centers and of high enantiomeric purity.

The novel furo[2,3-b][1,4]diazepines 7 have been synthesized in two steps from acetylenedicarboxylic acid esters and 4-amino-1-azabutadienes 1via their 1,3,2-diazasiline derivatives 2 and the crystal structure of 7a has been determined.

Michael addition reactions of ketone and ester lithium enolates to optically active Fischer vinylcarbene complexes derived from (-)-8-phenylmenthol take place with high syn selectivity and high levels of asymmetric induction. The initial Michael adducts can be further elaborated through diastereoselective addition of organometallic reagents to ketones and aldol reactions. Removal of the metal fragment and chiral auxiliary group leads to cyclic enol ethers with three or five contiguous stereogenic centers and of high enantiomeric purity.

A new type of cyclic amino-functionalized s-cis boroxyvinylcarbene complex of group 6 metals has been synthesized. These complexes underwent Diels−Alder-type reactions with 2-amino 1,3-dienes that proceeded with complete regioselectivity and high exo or endo diastereoselectivity, which was found to be highly dependent on the nature of the substituents on the diene. When chiral 2-amino-5-alkoxy dienes derived from (S)-prolinol benzyl or methyl ether were used, an exclusive exo and highly diastereofacially selective [4 + 2] cycloaddition was achieved, affording spiro carbene complexes with three contiguous stereogenic centers and a high level of enantiomeric purity. Removal of the Cr(CO)5 fragment and the BF2 group provided an entry to α,α-branched β-amino aldehydes or β-amino acids. In addition, the stable form of an amino-substituted hydroxycarbene complex of chromium was characterized by X-ray diffraction.

Formation of polycyclic structures within a few minutes: The intramolecular cyclization of diynes, activated by a benzenesulfenyl substituent, upon reaction with IPy2 BF4 proceeds as an efficient exo-endo coupling. A subsequent novel Friedel-Crafts-like ring closure provides the product [Eq. (1)]. Thus, intra- and intermolecular cyclizations can be carried out.

The proton form of the exchanger Na{sub 2}Ti{sub 2}O{sub 3}(SiO{sub 4}){center_dot}2H{sub 2}O exhibits a high selectivity for Cs{sup +} even in acid solutions. A neutron diffraction study was carried out to locate the position of the exchangeable protons. The structure contains cubane-like Ti{sub 4}O{sub 4} clusters bridged by silicate groups. The acidic proton is located on the cubane oxygens which make them four-coordinate, being bonded to three titaniums and one proton. The unit cell is tetragonal. There are six water molecules per tunnel and two tunnels per unit cell. Thus, the empirical formula is Ti{sub 2}(OH){sub 2}OSiO{sub 4}{center_dot}1.5H{sub 2}O. The water molecules are H-bonded to the framework oxygens and to each other. Although the tunnels are filled with water molecules, framework sites normally occupied by Na{sup +} are empty. The high selectivity for Cs{sup +} apparently stems from the ability to form a thermodynamically stable eight-coordinate complex by replacement of the hydroxyl protons.

Enantiomerically pure orthogonally N,N′-diprotected azaprolines 1 and 2,4-diaminoalcohols 2 are readily accessible by [3+2] cycloaddition of (−)-8-phenylmenthol-derived alkenyl Fischer carbene complexes 3 with diazomethane derivatives.

A sodium niobium(V) tetrasilicate, Na2H(NbO)Si4O11·1.25H2O (1), was synthesized hydrothermally at 190 °C from a mixture of silicic acid, NaOH, NbCl5, and H2O2 and added hydrochloric acid. The successive treatment of 1 with nitric acid yielded HNb(H2O)Si4O11·H2O (2). Contact of 2 with cesium hydroxide solutions converted it to the partially exchanged Cs+ phase Cs0.66H0.33Nb(H2O)Si4O11 (3). The three structures were solved from X-ray powder diffraction data. All compounds crystallize in the monoclinic space group P21/m with Z = 2, containing the Si8O2212- anion. This new silicate anion type is related to the Si4O116- unit, which is present in the amphibole series. The difference between both anion types lies in the chain periodicity: two for amphiboles or four for the new niobium silicates. These niobium silicates have framework structures enclosing tunnels in which the alkali cations reside.