Search results for "medium"
showing 10 items of 3746 documents
Modes of complexation of non-substituted and substituted tetraazamacrocycles with Group 6 metal carbonyls. X-ray structure of [(permethylcyclam)Mo(CO…
1995
Abstract Reactions of complexation of tetraazamacrocycles L with Group 6 metal carbonyls [M(CO)6](M = Cr, Mo, or W) lead to [LM(CO)4], [LM(CO)3] or [LM(CO)2] entities, depending both on the size of the macrocycle and on the metal M. The structure of one representative complex [(permethylcyclam)Mo(CO)4] has been determined by X-ray diffraction (permethylcyclam: 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane).
The role of metal oxides as promoters of V2O5/γ-Al2O3 catalysts in the oxidative dehydrogenation of propane
1997
Summary The physicochemical properties of potassium-, bismuth-, phosphorous- and molybdenum-doped (Me/V atomic ratios of 0 to 1) V 2 O 5 /γ-Al 2 O 3 catalysts and their catalytic behavior in the oxidative dehydrogenation of propane have been compared. The incorporation of metal oxides modifies the catalytic behavior of alumina-supported vanadia catalysts by changing both their redox and their acid-base properties. In this way, the addition of potassium leads to the best increase in the selectivity to propylene. This performance can be related to the modification of the acid character of the surface of the catalysts. The possible role of both redox and acid-base properties of catalysts on th…
Preparation and characterization of organofunctionalized bentonite clay bearing aminophosphonic groups in heavy metal uptake
2019
Abstract Bentonite (Bnt) with covalently immobilized N-propylaminodi(methylenephosphonic) groups (Bnt-ADPA) was obtained through a two-step synthesis including aminosilanization and phosphorylation of resulting aminobentonite through Moedritzer-Irani reaction. The grafting of an aminosilane layer in the interplanar space of the bentonite was investigated by XRD, and the presence of N and P-containing groups was confirmed by FTIR, 31P and 29Si MAS NMR. The immobilization of the organic functional groups increased the interplanar distance in bentonite matrix at 52% that essentially improved filtration properties compared to raw bentonite. The number of surface acid groups was evaluated to 0.8…
Synthesis, structure and biological properties of several binary and ternary complexes of copper(II) with ciprofloxacin and 1,10 phenanthroline
2009
In this study, a new binary complex [Cu(HCip) 2 ](NO 3 ) 2 · 6H 2 O ( 1 ) has been synthesized and then characterized by X-ray structure analyses. In this compound, each ciprofloxacin acts as a bidentate ligand resulting in a crystallographically planar configuration; the nitrate anions are located in apical positions with an axial distance significantly larger than the equatorial distances, which would be consistent with a very weak metal ion interaction due to the Jahn–Teller effect. In addition, both the synthesis and characterization of two new ternary complexes of ciprofloxacin–copper(II)–1,10-phenanthroline, [Cu(phen)(Cip)](NO 3 ) · 4H 2 O ( 2 ) and Cu(phen)(HCip)(NO 3 ) 2 · H 2 O (…
Fully interlocked three-dimensional molecular scaffolding: Synthesis, X-ray structure, magnetic and nitrogen sorption study
2012
Abstract The reaction of M(NO3)2·6H2O (M = Co or Ni), N,N-diethyl-ethylenediamine (deen) and sodium dicyanamide (dca) afforded the complex {[M(deen)(μ1,5-dca)2]}n (where for 1, M = Co and for 2, M = Ni). The complexes have been characterized structurally and magnetically. X-ray analysis reveals that the isomorphous complexes 1 and 2 feature similar infinite three-dimensional scaffolding-like structure to generate the fascinating molecular assembly. All the {N(CN)2}− ligands present in the complexes are connected to the symmetry related metal centers in an end-to-end fashion through bent {N(CN)2}− ligands. The zigzag linkage propagates parallel to three crystallographic axes to form a fully …
Synthesis, crystal structure and magnetic properties of the chiral iron(II) chain [Fe(bpym)(NCS)2]n (bpym = 2,2′-bipyrimidine)
1996
Abstract The iron(II) compound of formula [Fe(bpym)(NCS)2]n (bpym = 2,2′-bipyrimidine) has been synthesized and its crystal structure determined by X-ray diffraction methods. It crystallizes in the tetragonal P41 (No. 76) and P43 space groups, a = 8.849(2), c=16.486(3) A , V=1290.9(5) A 3 , Z=4, D c =1.699 g cm −3 , M r =330.2, F(000)=664, λ( Mo K α)=0.71073 A , μ( Mo K α)=14.8 cm −1 and T=295 K. A total of 2449 reflections was collected over the range 3≤2ϑ≤55°; of these, 1657 were unique and 1321 were considered as observed (13σ(I)) and used in the structural analysis. The final R and Rw residuals were 0.027 and 0.026, respectively. The structure is made up of chiral (Δ and Λ enantiomers c…
Metallophilic interactions in stacked dinuclear rhodium 2,2'-biimidazole carbonyl complexes
2012
Non-covalent metallophilic interactions were studied by investigating the stacking of two neutral rhodium complexes [Rh2I(R2bim)Cl2(CO)4] (R = Et, ethyl or Pr, propyl) in the solid state. Both dinuclear complexes formed infinite arrays of square planar d8 rhodium centres with intramolecular Rh⋯Rh distances of 3.1781(5) A (R = Et) and 3.1469(3) A (R = Pr) and the intermolecular Rh⋯Rh distances of 3.4345(6) A (R = Et) and 3.4403(3) A (R = Pr) between the adjacent molecules. The crystalline solids were stable and did not contain any solvent of crystallization. The effect of the metallophilic interactions on the absorption properties were studied using TD-DFT methods. The computational results …
Metal complexes of sulfanilamide derivatives. Crystal structure of [Zn(sulfathiazole)2]·H2O
1993
Abstract The crystal structure of the Zn(sulfathiazole) 2 ·H 2 O complex is reported. The complex crystallizes in the monoclinic space group C 2/ c . The cell dimensions are a = 9.098(3) A, b = 17.871(5) A, c = 14.61(1) A, β = 99.44(6)°, V = 2343(2) A 3 , Z = 4, and D x = 1.68 g/cm 3 . The final conventional R-factor = 0.027 for 2669 “observed” reflections and 191 variables. The Zn ion is surrounded in a regular tetrahedral arrangement by two N amino and two N thiazole atoms pertaining to four sulfathiazole (Hstz) ligands. Each stz anion, acting as a bidentate ligand, chelates to two Zn ions as a bridge through the N thiazole and the N amino atoms. The IR, 13 C NMR in solid state, 1 H NMR, …
Adsorption and activation of O2 at Au chains on MgO/Mo thin films
2010
We have investigated the adsorption of O(2) on Au(n) clusters (n = 1-6) supported by an ultra thin (3ML)MgO(001) film on Mo metal via density functional theory calculations. On thin films, these small clusters have chain like structures and their electronic states resemble 1D quantum well states. The Au(1-3) are charged by one electron whereas the larger Au(4-6) get two electrons from the substrate. This is confirmed both by the symmetries of the HOMO and LUMO states of the clusters and the Bader charge analysis. In contrast to the O(2) adsorption on gas-phase clusters, the adsorption energy of O(2) molecule does not show pronounced oscillations as a function of cluster size. The O(2) is ac…
A Combined Experimental and Theoretical Study on Bis(μ‐alkoxo)diiron(III) Complexes with Hydroxybenzylaminoethanol [O,N,O] Donor Ligands: Syntheses, …
2011
Three new neutral bis(μ-alkoxo)diiron(III) complexes were prepared from N(R),N-(2-methylene-4,6-di-tert-butylphenol)aminoethan-1-ol ligands (H2L1, R = Me and H2L2, R = H). In these complexes, the ligand wraps around the metal center exhibiting a tridentate facial coordination mode with alkoxo-bridging oxygen, amine nitrogen and phenoxo oxygen donor atoms. In the complex [Fe(acac)L1]2·MeCN (1) acetylacetonato coligand complete the distorted octahedral coordination spheres of the iron(III) ions, whereas in the five-coordinate iron(III) chloride complexes [FeClL1]2 (2) and [FeClL2]2 (3) the ligands induce a geometry that is intermediate between square pyramidal and trigonal bipyramidal. Magnet…