Salim F. Haddad

One Step Synthesis of NiO Nanoparticles via Solid-State Thermal Decomposition at Low-Temperature of Novel Aqua(2,9-dimethyl-1,10-phenanthroline)NiCl2 Complex

[NiCl2(C14H12N2)(H2O)] complex has been synthesized from nickel chloride hexahydrate (NiCl2·6H2O) and 2,9-dimethyl-1,10-phenanthroline (dmphen) as N,N-bidentate ligand. The synthesized complex was characterized by elemental analysis, infrared (IR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy and differential thermal/thermogravimetric analysis (TG/DTA). The complex was further confirmed by single crystal X-ray diffraction (XRD) as triclinic with space group P-1. The desired complex, subjected to thermal decomposition at low temperature of 400 ºC in an open atmosphere, revealed a novel and facile synthesis of pure NiO nanoparticles with uniform spherical particle; the structure of the NiO nanoparticles product was elucidated on the basis of Fourier transform infrared (FT-IR), UV-vis spectroscopy, TG/DTA, XRD, scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDXS) and transmission electron microscopy (TEM).

Effect of intermolecular interactions on the molecular structure; theoretical study and crystal structures of 4-bromopyridinium tetrafluoroborate and diaqua(3-bromopyridine)difluorocopper(II)

The role of C–Br⋯F interactions in two crystal structures (4BP)BF4 (I) and Cu(H2O)2(3bp)F2 (II), (where 4BP is the 4-bromopyridinium cation and 3bp is 3-bromopyridine) is investigated. Crystal structure analysis indicates that the supramolecular assembly of I is based on symmetrical bifurcated C–Br⋯F halogen bonding and the bifurcated N–H⋯F hydrogen bonding, while that of II is based on O–H⋯F hydrogen bonding interactions. The Br⋯F distance in I is 0.13 A less than the sum of van der Waals radii. In contrast, the Br⋯F distance in II is 0.04 A longer than the sum of van der Waals radii, indicating that the C–Br⋯F interaction plays a minor role in developing the supramolecular structure of II. The structure of I is the first reported with perfect symmetrical bifurcated C–Br⋯F halogen bonding. II is the first reported crystal structure with C–Br⋯F–tM interactions, tM = transition metal. Theoretical calculations have shown that a charge assisted symmetrical bifurcated C–Br⋯F interaction is stronger than the corresponding linear one, whereas in the normal (not charge assisted) C–Br⋯F halogen bonding both linear and bifurcated interactions have comparable strength. This conclusion is supported by structure analysis of reported structures in this work and the published data in Cambridge Structural Database (CSD).

Biotransformation of methyl cholate by Aspergillus niger.

Biotransformation of methyl cholate using Aspergillus niger was investigated. This led to the isolation of two derivatives: methyl 3alpha,7alpha,12alpha,15beta-tetrahydroxy-5beta-cholan-24-oate identified as a new compound, and a known compound methyl 3alpha,12alpha-dihydroxy-7-oxo-5beta-cholan-24-oate. The structure elucidation of the new compound was achieved using 1D and 2D NMR, MS and X-ray diffraction.

Copper–halide bonds as magnetic tunnels; structural, magnetic and theoretical studies of trans-bis(2,5-dibromopyridine)dihalo copper(II) and trans-bis(2-bromopyridine)dibromo copper(II)

The magneto-structural correlations in Cu(25dbp)2X2 and Cu(2bp)2Br2, where 25dbp = 2,5-dibromopyridine, X = Cl or Br, and 2bp = 2-bromopyridine have been investigated. The supramolecular structures of Cu(25dbp)2X2 are based on C–Br⋯X–Cu halogen bonding interactions. The temperature dependence of the susceptibility of Cu(25dbp)2Cl2 is best represented by an antiferromagnetic chain model. This agrees with the supramolecular structure; Cu(25dbp)2Cl2 molecules form linear chains of Cu–Cl⋯Cl–Cu structural units. In contrast, the magnetic susceptibility of Cu(25dbp)2Br2 is best represented by a ferromagnetic chain model; Cu(25dbp)2Br2 molecules form a chain structure based on Cu⋯Br2⋯Br–Cu where Br2 is the bromine atom on position 2 of the 2,5-dibromopyridine ligand. The susceptibilities of Cu(2bp)2Br2 indicate that the magnetic exchange interaction is very weak, even though Cu(2bp)2Br2 forms an isostructural chain structure similar to that observed in Cu(25dbp)2Br2. This paramagnetic behavior might be due to the presence of competitive antiferromagnetic and ferromagnetic exchange pathways. The shortest Cu–Br⋯Br–Cu distance is 4.5 A in Cu(2bp)2Br2, where Br is the bromide ligand, whereas the shortest inter-bromide ligand distance is 5.4 A in Cu(25dbp)2Br2. The two-bromide exchange pathway is known to be antiferromagnetic. This analysis is supported by DFT/B3LYP calculations. Calculations show that there is a significant spin density on the halide ligands, whereas, only a small spin density resides on Br2 (organic bromine). Also, the calculated spin density surface shows the presence of a spin end-cap along the Cu–X bond, which can rationalize the two-halide exchange pathway. In addition, theoretical calculations reveal that the two-halide exchange pathway in CuX2L2 compounds is stronger than the corresponding interaction in [CuX42−] compounds.

A new mixed multi-metallic calcium–cobalt-phosphotungstate with nano wheel-like polyanion: Na6Ca3[Ca2(H2O)6Co9(OH)3(H2O)6(HPO4)2(PW9O34)3]

A new 3-D wheel-like calcium–cobalt phosphotungstate, Na6Ca3[Ca2(H2O)6Co9(OH)3(H2O)6(HPO4)2(PW9O34)3], is reported and characterized by IR, UV, and single-crystal X-ray diffraction. The crystal structure consists of an infinite 3-D array of [Ca2(H2O)6Co9(OH)3(H2O)6(HPO4)2(PW9O34)3]12− anions (1) connected by sodium and calcium metal cations. The novel feature is the presence of two Ca2+, bonded to oxygen of HPO4− and to H2O spanning opposite sides in the complex anion. The stability of the crystalline product and its morphology were studied by SEM-EDX and DSC techniques.

Crystal structures of bis(4-dimethylaminopyridinium) tetrachlorocobaltate(II) and bis-[1,3-di (ammoniummethyl)benzene]tetrachlorocobaltate(II)

The crystal structures consist of organoammonium cations hydrogen bonded to tetrahedral CoCl42− anions. In the 4-dimethylaminopyridinium salt, [(CH3)2NC5H5NH]2CoCl4, pairs of cations hydrogen bond in an asymmetric fashion to two of the chlorines in each anion. The planar cations form two sets of π–π stacks, first parallel to the a axis and the second parallel to the b axis. The anions lie between these two nonintersecting sets of stacks. In contrast, for the second compound, [C6H4(CH2NH3)2]CoCl4, the tetrahedral CoCl42− anions form layers lying parallel to the bc plane. The 1,3-di(ammoniummethyl)benzene cations crosslink adjacent anionic layers, forming a lamellar structure of alternating organic and inorganic layers.

Crystal structure of bis(4-dimethylaminopyridinium) tribromocuprate(I) and bis(4-dimethylaminopyridinium) tetrabromocuprate(II)

The synthesis and crystal structures of two copper bromide salts of the 4-dimethylaminopyridinium (4DMAP+) cation are reported. The Cu(I) salt, (4DMAP)2CuBr3, crystallizes in the monoclinic space group C2/c, with a = 11.724(2), b = 11.055(3), c = 15.763(3) Å, β = 107.64(3)°, and Z = 4. It contains isolated planar 4DMAP+ cations and trigonal planar CuBr32− anions. Small distortions from idealized D3h symmetry are observed for the anion. For the Cu(II) salt, (4DMAP)2CuBr4, a triclinic cell is observed with a = 8.2373(2), b = 9.2428(2), c = 14.4391(1) Å, α = 93.760(1), β = 94.576(1), γ = 105.249(1)°, and Z = 2. This compound contains discrete planar 4DMAP+ cations and flattened tetrahedral CuBr42− anions. Small distortions are observed for ideal D2d symmetry.

fac-Tri­carbonyl­chloro(1,10-phenanthroline)­rhenium(I)

The title compound, [Re(C12H8N2)(CO)3Cl], contains isolated molecular units. Rhenium(I) is six-coordinated by the two N atoms of 1,10-phenanthroline, three carbonyls and one chloride anion. The coordination sphere is a distorted octahedron, with the chloride anion trans to one of the carbonyls. There is a significant trans influence, which lengthens one of the Re—C bonds by ca. 0.05 A. The bidentate 1,10-phenanthroline deviates slightly from planarity, with a dihedral angle between its two heterocyclic rings of 5.5 (3)°, and is folded away from the chloride anion. The Re(I) atom lies 0.192 (3) A from the least-squares plane of 1,10-phenanthroline. There are no π ring interactions between adjacent 1,10-phenanthroline rings.

Polymerized isomers of CuCl2(C8H12N2S2). The X-ray crystal structures of dichloro(5,5'-6,6−-tetrahydro-2,2'-bi-4H-1,3-thiazine-N3,N3')copper(II) and di-μ-chloro-bis[chloro(5,5'-6,6'-tetrahydro-2,2'-bi-4H-1,3-thiazine-N3,N3')copper(II)]

SummaryThe monomer in the title was obtained as a first crop and the dimer as a second crop from a 95% ethanolic solution of CuCl2 and 5,5′-6,6′-tetrahydro-2,2′-bi-4H-1,3-thiazine (2,2′-bi-2-thiazine) in the mole ratio 1∶1.1. The monomeric crystals are blue, dichloro(5,5′-6,6′-tetrahydro-2,2′-bi-4H-1, 3-thiazine- N3,N3′)copper(II).The crystal consists of monomeric molecules with no short contacts to neighbouring molecules. The Cu atoms occupy special positions on 2-fold axes. The bidentate 2,2′-bi-2-thiazine bonds via N as it assumes a cis configuration with a twist of 10.3° about the inter-ring C—C bond. The Cu—N distance is 2.013(5) Å, and Cu—Cl is 2.231(2) Å. Coordination around Cu is slightly distorted square planar with a dihedral angle of 5.8(2)° between the Cu, N, Cl plane and Cu, N′, Cl′ plane. The dimeric crystals are green, di-μ-chloro-bis[chloro(5,5′-6,6′-tetrahydro-2,2′-bi-4H-1, 3-thiazine-N3,N3′)copper(II)].The structure consists of discrete centrosymmetric dimers [CuCl2(C8H12N2S2)]2. Coordination around Cu is distorted square pyramidal (τ = 0.32) with two N atoms from the bidentate 2,2′-bi-2-thiazine occupying adjacent basal sites, and two Cl atoms occupying the other two basal sites. The average Cu—N distance is 2.028(4) Å, Cu—Cl(1) is 2.284(2) Å, Cu—Cl(2) is 2.239(1) Å. Dihedral angle between the CuN2 and CuCl2 planes is 23.7°. Cl(1)′ of the adjacent inversion-related monomer, CuCl2-(C8H12N2S2), occupies the apical position. Cu—Cl(1)′, r = 2.618(2) Å. Dimensions in the chloride-bridged planar dimeric moiety, Cu2Cl2, are Cu ⋯ Cu′ 3.449(1) Å; Cl(1) ⋯ Cl(1)′ 3.498(2) Å; Cu—Cl(1)—Cu′, φ = 89.2(1)°, φ/r = 34.07°/Å. The two saturated rings in C8H12N2S2 show a twist of 11.4° about the inter-ring C—C bond.

X-ray single-crystal structure of a novel di-μ-chloro-bis[chloro(2,9-dimethyl-1,10-phenanthroline)nickel(II)] complex: synthesis, and spectral and thermal studies

A binuclear nickel(II) chloride complex with dimethyl-1,10-phenanthroline, di-μ-chloro-bis[chloro(2,9-dimethyl-1,10-phenanthroline)nickel(II)] dimer, has been prepared and its molecular structure determined by X-ray diffraction. The crystal is triclinic, space group P−1, with the Ni(II) in [NiCl2(C14H12N2)]2 coordinated to two N of the phen ligand and three Cl−, one terminal and two bridging. A center of inversion lies midway between two Ni(II). Overall Ni(II) coordination is distorted triangular bipyramidal. The dimer complex was also characterized by elemental analysis, FAB-MS, IR and UV–visible spectroscopy, and thermogravimetric analysis.