Search results for "SED"
showing 10 items of 21612 documents
Insight into the Mechanism of Water Adsorption/Desorption in Hydrophilic Viologen-Carboxylate Based PCP
2017
A water stable and highly hydrophilic porous coordination polymer based on viologen-carboxylate type ligand, the 4,4′-bipyridinium,1,1-bis(3-carboxyphenyl) (pc2), is obtained by the solvothermal method: [Cd3(pc2) (BTC)2(H2O)2]·6H2O ([1(H2O)2]·6H2O; BTC3– = 1,3,5-carboxybenzene). Its crystal structure and the ones of two partially dehydrated phases have been determined, allowing insight into the mechanism of water adsorption/desorption of this PCP material. It is shown that the dehydrated compound [1] first adsorbs two water molecules which fill the pores, leading to [1]·2H2O. On the other hand, the partial dehydration of the as-synthesized compound leads to the intermediate phase [1(H2O)]·3…
New crystal structures of fluorinated α-aminophosphonic acid analogues of phenylglycine
2020
The four novel phosphonic acid analogues of phenylglycine with various substituents in phenyl ring (mostly fluorine atoms) have been synthesized by using procedure of amidoalkylation of phosphorus trichloride with aromatic aldehydes and acetamide. The NMR, ESI-MS spectroscopy, and single-crystal X-Ray diffraction methods were used to characterize unusual structures: the amino-(4-trifluoromethylbenzyl)-(1), amino-(3,4-difluorobenzyl)-(2), amino-(2,4,6-trifluorobenzyl)-(3), and amino-(2-fluoro-4-hydroxybenzyl)-(4) phosphonic acids. Since the α-aminophosphonates have a potential for biological activity and could be used as building blocks in medicinal chemistry, it is important to know their d…
Exploratory Synthesis of Low-Silica Nanozeolites through Geopolymer Chemistry
2019
Nanozeolites are of great interest with the premise of their efficiency in traditional applications such as catalysis and separation, as well as their emerging applications including chemical sensors, medicine, and food industry. We report a new geopolymerization route for the synthesis of nanozeolites with different crystal structures by exploring the Na–Al–Si–H2O quaternary phase space under a mild hydrothermal condition. Nanostructured faujasite (FAU), cancrinite (CAN), and sodalite (SOD) zeolites with a crystallite size smaller than 40 nm were successfully produced from our exploration, as well as a submicron-sized Linde-Type A (LTA) zeolite. The transmission electron microscopy and nit…
A Generalized Semiempirical Approach to the Modeling of the Optical Band Gap of Ternary Al-(Ga, Nb, Ta, W) Oxides Containing Different Alumina Polymo…
2021
A generalization of the modeling equation of optical band gap values for ternary oxides, as a function of cationic ratio composition, is carried out based on the semiempirical correlation between the differences in the electronegativity of oxygen and the average cationic electronegativity proposed some years ago. In this work, a novel approach is suggested to account for the differences in the band gap values of the different polymorphs of binary oxides as well as for ternary oxides existing in different crystalline structures. A preliminary test on the validity of the proposed modeling equations has been carried out by using the numerous experimental data pertaining to alumina and gallia p…
Water-Soluble Squaramide Dihydrates: N-Methylation Modulates the Occurrence of One- and Two-Dimensional Water Clusters through Hydrogen Bonding and D…
2018
Water confined in molecular size domains is distinct to bulk water. The altered interactions between adjacent water molecules, and between water molecules and molecular wall components of the confinement system, determine aspects of important phenomena in material science, biology, and nanotechnology. The structural determination of confined water, however, has proven to be challenging. Here, we describe the crystal structures of three related squaramides 1–3 whose molecular structures are modulated by the gradual incorporation of N-methyl groups to the squaramide moiety. The three squaramides differ in their hydrogen bonding capabilities due to the different degree of N-methylation of each…
A polar/π model of interactions explains face-to-face stacked quinoid rings: a case study of the crystal of potassium hydrogen chloranilate dihydrate
2015
International audience; The nature of interactions between face-to-face staggered stacked quinoid rings with pi-systems, observed with a short inter-ring centroid. centroid distance, is analyzed by experimental and theoretical methods. Charge density studies based on X-ray diffraction and DFT calculations, complemented by impedance spectroscopy, were employed to define the electronic and structural characteristics of the quinoid rings responsible for their interactions within the crystal packing. The crystal packing is mainly stabilized by strong electrostatic interactions between the K+ cation and the hydrogen chloranilate anion. The proximity and orientation of the stacked quinoid rings i…
A family of heterotetrameric clusters of chloride species and halomethanes held by two halogen and two hydrogen bonds
2016
Two previously reported 1,3,5,7,9-pentaazanona-1,3,6,8-tetraenate (PANT) chloride platinum(II) complexes [PtCl{HNC(R)NCN[C(Ph)C(Ph)]CNC(R)NH}] (R = tBu 1, Ph 2) form solvates with halomethanes 1·1¼CH2Cl2, 1·1⅖CH2Br2, and 2·CHCl3. All these species feature novel complex-solvent heterotetrameric clusters, where the structural units are linked simultaneously by two C–X⋯Cl–Pt (X = Cl, Br) halogen and two C–H⋯Cl–Pt hydrogen bonds. The geometric parameters of these weak interactions were determined using single-crystal XRD, and the natures of the XBs and HBs in the clusters were studied for the isolated model systems (1)2·(CH2Cl2)2, (1)2·(CH2Br2)2, and (2)2·(CHCl3)2 using DFT calculations and Bad…
Enhancement of the Intermolecular Magnetic Exchange through Halogen···Halogen interactions in Bisadeninium Rhenium(IV) Salts
2017
Two novel ReIV salts of general formula [H2ade]2[ReIVX6]X2·4H2O [H2ade2+ = 9H-adenine-1,7-diium; X = Cl(1) and Br(2)] have been synthesized and magneto-structurally characterized. 1 and 2 are isostructural salts that crystallize in the orthorhombic system with space group Fdd2. Both compounds are made up of discrete mononuclear [ReIVX6]2- and X- anions and doubly protonated adenine cations. The six-coordinate rhenium(IV) ion is bonded to six halide ligands [X = Cl (1) and Br (2)] in an octahedral geometry. Short intermolecular ReIV−X···X−ReIV interactions, as well as ReIV−X···H−N(H2ade) and ReIV−X···H−Ow hydrogen bonds, are present in the crystal lattice of 1 and 2. Magnetic suscep-tibility…
A comparative study of methanol carbonation on unsupported SnO2 and ZrO2
2009
International audience; The aim of this work was to explore the catalytic properties of SnO2 in the coupling of methanol with carbon dioxide to afford dimethyl carbonate. SnO2 nanopowders were produced by hydrolysis of tin tetra-tert-butoxide dissolved in n-butanol. The samples were much more active than a commercial one due to their higher surface areas. In addition, they exhibited excellent recyclability. However, comparison with ZrO2, prepared and tested under the same experimental conditions, showed that zirconia-based catalysts were more selective and are, among the heterogeneous catalysts already reported, still the more selective. SnO2 also catalyzed the formation of dimethyl ether l…
Insights into the crystal packing of phosphorylporphyrins based on the topology of their intermolecular interaction energies
2014
Four metal complexes of 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrin 1M (M = Cd(II), Ni(II), Pd(II), and Pt(II)) were synthesized and crystallographically characterized. The crystal organization patterns were analyzed using DFT (B97-D3/def2-SVP) calculations of the intermolecular interaction energies between complexes in the crystals. For the systematic analysis of crystal packing, the calculations were extended to previously reported compounds 1M (M = H2, Cu(II), and Zn(II)). Quantitative analysis of the interaction energies shows the essential role of weak intermolecular interactions, such as C-H⋯O, C-H⋯π and M⋯π, in the formation of basic structural motifs and their organization …