Volume 229, Issue 4

The stannides Sm 6 Pd 10– x Sn 11 and Sm 3 Pd 5– x Sn 5 were synthesized from the elements by arc-melting. They were studied by powder and single-crystal X-ray data: C 2/ m , a   =  1720.45(10), b   =  451.97(2), c   =  1420.60(8), β   =  99.705(5)°, wR 2  =  0.086, 2076 F 2 values, 83 variables for Sm 3 Pd 4.95(1) Sn 5 and C 2/ m , a   =  1738.68(7), b   =  451.49(1), c   =  1692.68(7), β   =  121.375(3)°, wR 2  =  0.0335, 2164 F 2 values, 85 variables for Sm 6 Pd 9.82(1) Sn 11 . Both structures show small defects for one palladium site. The palladium and tin atoms in Sm 6 Pd 10– x Sn 11 and Sm 3 Pd 5– x Sn 5 build up complex three-dimensional polyanionic networks in which the samarium atoms fill cavities within distorted pentagonal channels. In addition to strong covalent Pd–Sn bonding, the polyanions are further stabilized by Pd–Pd and Sn–Sn bonding.

The intermetallic magnesium compounds RE 2 RuMg 3 ( RE = Dy, Ho, Er, Tm, Lu) and RE 3 Ru 2 Mg ( RE = Sc, Er, Lu) were synthesized from the elements in sealed niobium tubes in muffle or induction furnaces using different annealing sequences. The polycrystalline RE 2 RuMg 3 and RE 3 Ru 2 Mg samples were characterized through Guinier powder patterns. The structures of Er 2 RuMg 3 and Sc 3 Ru 2 Mg were refined on the basis of single-crystal X-ray diffractometer data: new type, P 4/ mmm , a = 336.71(9), c = 1234.6(7) pm, wR = 0.0327, 240  F val­ues, 12 variables for Er 2 RuMg 3 and a = 324.67(6), c = 1077.2(3) pm, wR = 0.0345, 273 F values, 12 variables for Sc 3 Ru 2 Mg. The Er 2 RuMg 3 and Sc 3 Ru 2 Mg structures are i3 superstructures of the CuAu type and thus belong to the large family of ordered bcc derivatives. The fundamental building units are distorted ErRu, ScRu, ScMg, and ErMg cubes. The magnesium-rich phase Er 2 RuMg 3 has a pronounced Mg substructure (314–337 pm Mg–Mg) with distorted cuboctahedral coordination. This sub­structure is compared to other magnesium-rich compounds. Temperature dependent magnetic susceptibility studies show Curie-Weiss paramagnetism for RE 2 RuMg 3 ( RE = Dy, Ho, Er, Tm) with experimental magnetic moments close to the RE 3+ free ion values. The compounds exhibit antiferromagnetic ordering at Néel temperatures of 6.5(1), 3.6(5), 3.5(5), and 5(1) K, respectively. Metamagnetic transitions underline the stable antiferromagnetic ground states. Lu 2 RuMg 3 is a Pauli paramagnet.

Crystal and molecular structures of 2 : 1 co-crystals formed between p -nitrophenylacetic acid and three isomeric n -pyridinealdazines, n = 2( 1 ), 3( 2 ) and 4( 3 ), are described in which the carboxylic acid is always in a general position and the respective n -pyridinealdazine is located about a centre of inversion. A common feature of the supramolecular aggregation is the formation of three-molecule aggregates sustained by the {… HOCO … N(py)} heterosynthon, further vindicating this as a most reliable synthon for co-crystal design. Molecules are assembled into three-dimensional architectures by C–H … O interactions coupled with C–H … π ( 1 ) or π … π ( 2 and 3 ) contacts.

Structural analysis of CO 2 -silicalite-1 crystals using the single-crystal X-ray diffraction method reveals that the crystal system is twinned monoclinic. The structure of silicalite-1 (MFI-type zeolites) loaded with CO 2 has previously been solved in orthorhombic system [1], but the R value is still large. Since CO 2 molecules are too small to maintain the orthorhombic structure, it is considered that the CO 2 -silicalite-1 crystals should be in the relaxed monoclinic twin phase. The diffraction data in the previous report is recalculated in P 2 1 /n as the monoclinic twinning.

The crystal structures are reported of N -[2-(1-benzenesulfonyl-1 H -pyrazol-3-yl)-6-methyl-phenyl]-benzenesulfonamide, 1 , and N -[2-(1-toluene-4-sulfonyl-1 H -pyrazol-3-yl)-6-methyl-phenyl]-benzenesulfonamide, 2 : two compounds used in a recently reported antileishmania study. The crystallographic study reveals significant differences in the conformations adopted by molecules of 1 compared to those adopted by the three independent molecules of 2 in the solid state. The conformation differences between molecules of 1 , on one hand, and the three molecules of 2 , on the other, are not driven by steric effects within the molecular arrangements. If molecules 2 adopted the molecular conformation found for 1 , severe steric interference would occur in the chains and other aggregates generated from the intermolecular contacts. As all the intermolecular interactions are of a weak nature, it is unlikely that aggregation would survive in dilute aqueous media, and hence the steric constraints on the conformations adopted in the solid state would not be in place in solution. Thus the difference in the solid state conformations offers no light on the greater activity of compound 1 compared to that of compound 2 in the antileishmania study in aqueous media.

The supramolecular complex [Mg(H 2 O) 6 Br 2 ] · [(C 7 H 14 N 4 ) 2 ] · 4 (H 2 O) ( 1 ) was synthesized and characterized by combination of techniques as NMR, FT-IR, elemental analysis and argentometric titration. The molecular structure was evidenced by X-ray crystallography. It underwent a spontaneous phase transition to a second monoclinic phase ( 2 ). Phase ( 1 ) crystallizes in the monoclinic space group P 2 1 / c with a  = 13.79430(12), b  = 14.80930(13), c  = 14.29182(12) Å, β  = 91.3976(5)°, and Z  = 4. The crystal structure was partially solved by direct methods from intensities obtained from a microcrystal of the material measured by single-crystal method, and finalized from powder data. The second phase ( 2 ) with monoclinic space group P 2 1 / a , a  = 9.19007(6), b  = 21.38080(17), c  = 8.12027(6) Å, β  = 113.7766(5)°, and Z  = 2, was solved from powder data, ab initio , by a charge flipping algorithm. The diffraction experiments showed an irreversible phase change occurs as a function of temperature with apparent gain of thermodynamic stability.

Phenacyl benzoates possess commercial importance due to their various applications in the fields of synthetic and photochemistry, such as photosensitive blocking groups owing to their ease of cleavage under mild conditions. In the present study, a series of ten new 2-(4-bromophenyl)-2-oxoethyl benzoates 2 ( a–j ), with the general formula Br(C 6 H 4 )COCH 2 OCO(C 6 H 5– n X n ), X = Cl, NO 2 or NH 2 , and n = 1 or 2, have been synthesized by reacting 4-bromophenacyl bromide with various substituted benzoic acids using potassium carbonate in DMF medium at room temperature. These reactions proceeded with ease under mild conditions producing high purity products in good yield. Each product was characterized by mass spectra, elemental analysis and melting points, its 3D structure was confirmed by single-crystal X-ray diffraction studies. The X-ray 3D structures showed the flexibility of the C(=O)–O–C–C(=O) connecting bridge in which 7 out of 10 compounds tend to form a torsion angle in the range of 70 to 91°, whereas the rest are slightly twisted with a torsion angles of –160, 163, 176 and 178°. Their molecular conformations are in good agreement with another 22 related structures. These synthesized compounds were screened for their abilities for DPPH radical scavenging and ferric reducing anti-oxidant power. The results indicate that these compounds displayed mild anti-oxidant ability when compared to the standard anti-oxidant BHT.