Voici les éléments 1 - 10 sur 21
- PublicationMétadonnées seulementrac-(R)-2-[(2R,5R)-5-Methyltetrahydrofuran-2-yl]propanoic acidIn the crystal structure of rac-(R)-2-[(2R,5R)-5-methyltetrahydrofuran-2-yl]propanoic acid, C8H14O3, the 2,5-THF ring junction is cis. The relative configuration of position 2 in the propanoic acid group is the same as that in positions 2 and 5 in the THF ring. In the crystal structure, symmetry-related mols. are linked by O-H...O H bonds to form centrosym. dimers. Crystallog. data are given. [on SciFinder(R)]
- PublicationMétadonnées seulement2,2'-(Propane-2,2-diyl)bis(1H-pyrrole)2,2'-(Propane-2,2-diyl)bis(1H-pyrrole), C11H14N2, crystd. with 2 independent mols. (A and B) in the asym. unit. The 2 mols. differ only slightly, with the pyrrole rings being inclined to 1 another at a dihedral angle of 87.67(8)° in mol. A and 88.09(7)° in mol. B. In the crystal, there are no classical H bonds, but the 2 pyrrole NH groups of 1 mol. are involved in N-H···? interactions with the pyrrole rings of the other mol. In this manner, a compact box-like arrangement of the 2 independent mols. is formed. Crystallog. data are given. [on SciFinder(R)]
- PublicationMétadonnées seulement4-Methoxybenzoyl-meso-octamethylcalixpyrrolidinopyrrole: an acyl chloride derivative of a partially reduced calixpyrroleIn the title compd., C36H50N4O2, the two pyrrolidine rings have envelope conformations. The conformation of the macrocycle is stabilized by N-H···N H bonds and a C-H···N interaction. The benzoyl ring is inclined to an adjacent pyrrole ring by 6.76(9)°, with a centroid-to-centroid distance of 3.6285(10) Å. In the crystal, apart from a C-H···O and a C-H···? interaction, mols. are linked via an N-H···O H bond, giving helical chains propagating along . Crystallog. data and at. coordinates are given. [on SciFinder(R)]
- PublicationMétadonnées seulement2,2'-[(2S*,6R*)-Piperidine-2,6-diyl]dipropan-2-olIn the title compd., C11H23NO2, the piperidine ring has a chair conformation. The two hydroxy H atoms are disordered over two positions with fixed occupancy ratios of 0.57:0.43 and 0.63:0.37. In the mol., there are two short N-H···O interactions. In the crystal, four symmetry-related mols. are linked by O-H···O H bonds to form a cage-like arrangement, centered about the point of intersection of three 2-fold axes. These cages stack along the  direction. Crystallog. data and at. coordinates are given. [on SciFinder(R)]
- PublicationAccès libreSynthesis, crystal structures and magnetic properties of trinuclear oxo-centered homo- and mixed-valence manganese pivalate complexes with imidazole (Im) and 1-methylimidazole (1-MeIm): [Mn3III0(02CCMe3)6 (Im)3](Me3CC02)•0.5Me3CC02H and [Mn2IIIMnII0(02CCMe3)6(1-MeIm)3](2006)
;Baca, Svetlana G. ; ;Ambrus, Christina ;Malinovskii, Stanislav T. ;Malaestean, Iurii ;Gerbeleu, NicolaeDecurtins, SilvioTwo new μ3-oxo-centered trinuclear manganese complexes, one of them a homo-valence [Mn3III0(02CCMe3)6 (Im)3](Me3CC02)•0.5Me3CC02H (1) pivalate complex and the other a mixed-valence [Mn2IIIMnII0(02CCMe3)6(1-MeIm)3] (2) pivalate complex (where Im = imidazole, 1-MeIm = 1-methylimidazole), have been synthesized and characterized by IR spectroscopy, thermogravimetric analysis, X-ray crystallography and magnetochemistry. Complexes 1 and 2 are μ3-oxo-trinuclear compounds with the three manganese atoms bridged by six pivalate groups. At each axial position there is an Im (1) or 1-MeIm (2) molecule. In both compounds, the manganese coordination geometry is slightly distorted octahedral, consisting of the oxygen of the central triangle, four oxygen atoms from bridging pivalate ligands, and a terminal Im or 1-MeIm nitrogen atom. The crystal packing of 1 involves hydrogen bonding between complex cations [Mn3O(Piv)6(Im)3]+ and outersphere pivalate ions, whereas in compound 2 interactions of the C–Hπ type, formed by both the aromatic and methyl C–H groups of 1-MeIm molecules, are present. Magnetic studies reveal that both compounds represent antiferromagnetically coupled, spin-frustrated triangular systems exhibiting weak to moderate exchange coupling constants.
- PublicationMétadonnées seulementSynthesis, structure, and complexation properties of partially and completely reduced meso-octamethylporphyrinogens (calixpyrroles)Calixpyrroles bind anions efficiently and can be transformed into transition-metal complexes only under forcing conditions. Reducing the macrocycle creates a ligand that easily forms classical Werner complexes with Cu, Ni, and Pd ions. The metal complexes present an array of four directed H bonds, which specifically bind the counterions. [on SciFinder(R)]
- PublicationAccès libreSynthesis, structure and magnetic properties of two end-on double azido bridged nickel(II) dinuclear entities incorporating N,N,N-coordinating tridentate reduced Schiff base ligands(2006)
;Sarkar, Sumana ;Mondal, Amrita ;El Fallah, Mohamed Salah ;Ribas, Joan ;Chopra, Deepak ;Krishna Rajak, KajalComplexes of the general formula [Ni2L2 (μ1,1-N3)2(N3)2] have been synthesised in good yields by reacting Ni(NO3)2 • 6H2O with L in the presence of excess of sodium azide in methanol at room temperature. Here L is N,N-bis(2-pyridylmethyl)amine (L1) and N-(2-pyridylmethyl)-N′,N′-diethylethylenediamine (L2). The X-ray structures of both compounds reveal that the N,N,N coordinating reduced Schiff bases are ligated facially. The Ni–Nazido–Ni angle is 100° and the NiNi separation is 3.2 Å. The variable temperature magnetic susceptibility measurements of the two complexes show ferromagnetic behavior.
- PublicationMétadonnées seulement1,4-Bis(hexyloxy)-2,5-diiodobenzeneThe centrosym. title compd., C18H28I2O2, crystd. in the monoclinic space group P21/c with the alkyl chains having extended all-trans conformations, similar to those in the centrosym. bromo analog that crystd. in the triclinic space group P?1. The difference between the 2 structures lies in the orientation of the 2 alkyl chains with respect to the C(arom.)-O bond. In the title compd., the O-Calkyl-Calkyl-Calkyl torsion angle is 55.8(5)°, while in the bromo analog this angle is -179.1(2)°. In the title compd., the C-atoms of the alkyl chain are almost coplanar [max. deviation of 0.052(5) Å] and this mean plane is inclined to the benzene ring by 50.3(3)°. In the bromo-analog, these 2 mean planes are almost coplanar, making a dihedral angle of 4.1(2)°. Another difference between the crystal structures of the 2 compds. is that in the title compd. there are no halide...halide interactions. Instead, symmetry-related mols. are linked via C-H...? contacts, forming a 2D network. Crystal data: monoclinic, P21/n, a = 9.441(9), b = 7.8455(6), c = 13.457(2) Å, ? = 92.148(12)°, Z = 2, 1216 obsd. reflections with I > 2(I), 101 refined parameters, R[F2 > 2?(F2)] = 0.029, wR(F2) = 0.055. [on SciFinder(R)]
- PublicationMétadonnées seulement2-(2-Naphthyl)-1,3-dioxaneThe title compd., C14H14O2, crystallizes in the chiral monoclinic space group P21. Crystallog. data and at. coordinates are given. This acetal is composed of a planar naphthalene ring with a 1,3-dioxane ring substituent, which has a chair conformation. In the crystal structure, symmetry-related mols. are connected via a weak C-H...O interaction to form a helical chain propagating in . While there are no ?-? stacking interactions present, there are weak C-H...? interactions involving the naphthalene arom. rings, which link the helical chains to form a two-dimensional network in the (011) plane. [on SciFinder(R)]
- PublicationMétadonnées seulementSynthesis of α,β'- and β,β'-linked dimethoxycarbonyldipyrromethanes by Rothemund-type condensationThe Rothemund-type condensation of methoxycarbonylpyrrole with acetone produces mainly the α,β'-linked dipyrromethane, a building block for the synthesis of N-confused macrocycles. The influence of the reaction conditions on the regioselectivity of the process is reported. The x-ray structures of the α,α'-, α,β'- and β,β'-linked dipyrromethanes show an interesting discrimination of the structurally different types of hydrogen bonds. [on SciFinder(R)]