Crystal structures of three zinc(II) halide coordination complexes with quinoline N-oxide.

The reaction of one equivalent of zinc(II) halide with two equivalents of quinoline N-oxide (QNO) in methanol yields compounds as ZnX 2(QNO)2, where X = Cl (I), Br (II) and I (III), namely, di-chlorido-bis-(quinoline N-oxide-κO)zinc(II), [ZnCl2(C9H7NO)2], di-bromido-bis-(quinoline N-oxide-κO)zinc(II), [ZnBr2(C9H7NO)2], and di-iodido-bis-(quinoline N-oxide-κO)zinc(II) [ZnI2(C9H7NO)2]. In all three complexes, Zn cations are coordinated by two QNO ligands bound through the oxygen atoms and two halide atoms, with X-Zn-X bond angles ca 20° wider than the O-Zn-O, giving rise to a distorted tetra-hedral geometry. Crystals of (II) and (III) are isostructural and both show pairwise π-stacking of QNO ligands and weak C-H⋯X hydrogen bonds, while (I) packs differently, with a shorter C-H⋯Cl bond and without π-stacking.

Ethyl 1H-indole-2-carboxyl-ate.

Our work in the area of synthesis of tris indole compounds as a potential chelator led to the synthesis and crystallization of ethyl 1H-indole-2-carboxyl-ate, C11H11NO2, an indole that was synthesized by the thionyl chloride reaction of 1H-indole-2-carb-oxy-lic acid, followed by dissolution in ethanol. The mol-ecular packing exhibits a herringbone pattern with the zigzag running along the b-axis direction; the compound crystallizes as a hydrogen-bonded dimer resulting from O⋯H-N hydrogen bonds, between the indole N-H group and the keto oxygen atom, which build centrosymmetric R 2 2(10) ring motifs in the crystal.

Pyridine-4-carboxamidoxime N-oxide.

Our work in the area of synthesis of metal-organic frameworks (MOFs) based on organic N-oxides led to the crystallization of pyridine-4-carboxamidoxime N-oxide. Herein we report the first crystal structure of the title compound, C6H7N3O2 [systematic name: (Z)-4-(N'-hy-droxy-carbamimido-yl)pyridine N-oxide]. The hy-droxy-carbamimidoyl group is essentially coplanar with the aromatic ring, r.m.s.d. = 0.112 Å. The compound crystallizes in hydrogen-bonding layers built from the formation of strong O-H⋯O hydrogen bonds between the oxime oxygen atom and the oxygen atom of the N-oxide, and the formation of N-H⋯O hydrogen bonds between one amine nitro-gen atom and the N-oxide oxygen atom. These combined build R 3 4(24) ring motifs in the crystal. The crystal structure has no π-π inter-actions.

Crystal structures of four dimeric manganese(II) bromide coordination complexes with various derivatives of pyridine N-oxide.

Four manganese(II) bromide coordination complexes have been prepared with four pyridine N-oxides, viz. pyridine N-oxide (PNO), 2-methyl-pyridine N-oxide (2MePNO), 3-methyl-pyridine N-oxide (3MePNO), and 4-methyl-pyridine N-oxide (4MePNO). The compounds are bis-(µ-pyridine N-oxide)bis-[aqua-dibromido-(pyridine N-oxide)manganese(II)], [Mn2Br4(C5H5NO)4(H2O)2] (I), bis-(µ-2-methyl-pyridine N-oxide)bis-[di-aqua-dibromido-manganese(II)]-2-methyl-pyridine N-oxide (1/2), [Mn2Br4(C6H7NO)2(H2O)4]·2C6H7NO (II), bis-(µ-3-methyl-pyridine N-oxide)bis-[aqua-dibromido-(3-methyl-pyridine N-oxide)manganese(II)], [Mn2Br4(C6H7NO)4(H2O)2] (III), and bis-(µ-4-methyl-pyridine N-oxide)bis-[di-bromido-methanol(4-methyl-pyridine N-oxide)manganese(II)], [Mn2Br4(C6H7NO)4(CH3OH)2] (IV). All the compounds have one unique MnII atom and form a dimeric complex that contains two MnII atoms related by a crystallographic inversion center. Pseudo-octa-hedral six-coordinate manganese(II) centers are found in all four compounds. All four compounds form dimers of Mn atoms bridged by the oxygen atom of the PNO ligand. Compounds I, II and III exhibit a bound water of solvation, whereas compound IV contains a bound methanol mol-ecule of solvation. Compounds I, III and IV exhibit the same arrangement of mol-ecules around each manganese atom, ligated by two bromide ions, oxygen atoms of two PNO ligands and one solvent mol-ecule, whereas in compound II each manganese atom is ligated by two bromide ions, one O atom of a PNO ligand and two water mol-ecules with a second PNO mol-ecule inter-acting with the complex via hydrogen bonding through the bound water mol-ecules. All of the compounds form extended hydrogen-bonding networks, and compounds I, II, and IV exhibit offset π-stacking between PNO ligands of neighboring dimers.

Synthesis, stereochemical characterization, and antimicrobial evaluation of a potentially nonnephrotoxic 3'-C-acethydrazide puromycin analog.

Puromycin is a peptidyl nucleoside endowed with significant antibiotic and anticancer properties, but also with an unfortunate nephrotoxic character that has hampered its use as a chemotherapeutic agent. Since hydrolysis of puromycin's amide to puromycin aminonucleoside is the first metabolic step leading to nephrotoxicity, we designed a 3'-C-hydrazide analog where the nitrogen and carbon functionality around the amide carbonyl of puromycin are inverted. The title compound, synthesized in 11 steps from D-xylose, cannot be metabolized to the nephrotoxic aminonucleoside. Evaluation of the title compound on Staphylococcus epidermidis and multi-drug resistance Staphylococcus aureus did not show significant antimicrobial activity up to a 400 µM concentration.

Crystal structure of 2,6-di-chloro-4-nitro-pyridine N-oxide.

In the title compound, C5H2Cl2N2O3, the nitro group is essentially coplanar with the aromatic ring, with a twist angle of 4.00 (6)° and a fold angle of 2.28 (17)°. The crystal structure exhibits a herringbone pattern with the zigzag running along the b axis. The herringbone layer-to-layer distance is 3.0075 (15) Å, with a shift of 5.150 (4) Å. Neighboring mol-ecules are tilted at a 57.83 (4)° (ring-to-ring) angle with each other. The nitro group on one mol-ecule points to the N-oxide group on the neighboring one, with an inter-molecular O⋯N(nitro) distance of 3.1725 (13) Å.

Crystal structure of 3-bromo-pyridine N-oxide.

In the title compound, C5H4BrNO, there are two mol-ecules in the asymmetric unit that are related by a pseudo-inversion center. The two independent mol-ecules are approximately planar, with an observed (ring-ring) angle of 5.49 (13)°. The crystal structure exhibits a herringbone pattern with the zigzag running along the b-axis direction. The least-squares plane containing the rings of both asymmetric molecules and the plane containing the symmetrically related mol-ecules make a plane-plane angle of 66.69 (10)°, which makes the bend of the herringbone pattern. The bromo group on one mol-ecule points to the bromo group on the neighboring mol-ecule, with a Br⋯Br inter-molecular distance of 4.0408 (16) Å. The herringbone layer-to-layer distance is 3.431 (4) Šwith a shift of 1.742 (7) Å. There are no short contacts, hydrogen bonds, or π-π inter-actions.

A square-planar hydrated cationic tetrakis(methimazole)gold(III) complex.

The cationic pseudo-square-planar complex tetrakis(1-methyl-2,3-dihydro-1H-imidazole-2-thione-κS)gold(III) trichloride sesquihydrate, [Au(C4H6N2S)4]Cl3·1.5H2O, was isolated as dark-red crystals from the reaction of chloroauric acid trihydrate (HAuCl4·3H2O) with four equivalents of methimazole in methanol. The Au(III) atoms reside at the corners of the unit cell on an inversion center and are bound by the S atoms of four methimazole ligands in a planar arrangement, with S-Au-S bond angles of approximately 90°.