Rencontre avec l'expert: l'Ocytocine, une piste thérapeutique en Psychiatrie

The behavior of a sterically crowded neutral pincer {2,6-bis[(di-t-butylphosphino)methyl]-phenyl}palladium (PCPPd) halides, PCPPdX (X = Cl, Br or I), as XB acceptors with strong halogen bond (XB) donors, iodine (I2), 1,4-diiodotetrafluorobenzene (F4DIBz), and 1,4-diiodooctafluorobutane (F8DIBu) were studied in the solid state. The co-crystallization experiments afforded high-quality single crystals of XB complexes PCPPdClI2 (1a), PCPPdBrI2 (2a), PCPPdII2 (3a), PCPPdClF4DIBz (1b), PCPPdBrF4DIBz (2b), and PCPPdBr F8DIBu (2c). The 1:1 iodine complexes (1a, 2a, and 3a) all showed a strong halogen bonding interaction, the reduction of the sum of the van der Waals radii of halogen to iodine being 24.6 (1a), 23.9 (2a), and 19.4% (3a) with XII angles of 177, 176, and 179, respectively. While the pincer palladium chloride 1 and bromide 2 were crystallographically isomorphous and showed similar XB behavior, the palladium iodide complex, 3, exhibited markedly different properties, and unlike 1 and 2 it does not, under similar conditions, result in XB complexes with the weaker XB donors F4DIBz and F8DIBu. The results indicate that PCPPdI is not nucleophilic enough to have XB interactions with other donors than iodine. However, the weaker XB donors F4DIBz and F8DIBu form XB complexes with the chloride 1 and especially with the bromide 2. The prevalence of the halogen bonding with 2 is probably not only electronic in origin, and it seems to offer the best balance between electron poorness and steric availability. The XB interactions with F4DIBz and F8DIBu are much weaker than with iodine, the reduction of the sum of the van der Waals radii of halogen to iodine being 13.5, 12.3, and 14.6% with CIX angles between 163 and 179 for 1b, 2b, and 2c, respectively, and results in polymeric (1F4DIBz1F4DIBz)n, (2F4DIBz2F4DIBz)n, and (2F8DIBu2F8DIBu)n one-dimensional zigzag chains in the solid state

Network analysis of bicyclo[3.3.1]nonanes: the diol, the dione and the acetal

The solid state structure of endo,endo-bicyclo[3.3.1]nonane-2,6-diol, rac-2, shows a hydrogen bonded, three-connected, chiral 3D-net with utg-topology, distinctively different from those formed by the so called tubuland diols, e.g. 2,6-dimethylbicyclo[3.3.1]nonane-exo2, exo-6-diol, rac-5, that crystallise as three-connected, chiral etanets and from the qtz-net formed by weaker hydrogen bonds in the bicyclo[3.3.1]nonane-2,6-dione, 3. The protected bicyclo[3.3.1]nonane2,6-dione, bis-2,6-ethylenedioxy acetal, 4, has a structure governed by weaker forces and can be interpreted as close packed stacks

Synthesis, EPR and DFF calculations of rare Ag(II)porphyrins and the crystal structure of [Zn(II)tetrakis(4-bromo-2-thiophene)porphyrin]

Meso-tetrakis (4-bromo-2-thiophene) and (5-bromo-2-thiophene) porphyrins were synthesized in 18% yield from freshly distilled pyrrole and the corresponding aldehydes in refluxing propionic acid. Reaction of both porphyrins with either Zn(OAc)(2)center dot 2H(2)O Or Ag(OAc) afforded the corresponding metal complexes in 20% yield. The free bases and metal complexes were characterized by IR, NMR, EPR, MS and XPS. The crystal structure of 5,10,15.20(4-bromo-2-thiophene)porphyrinato Zn(II) was determined by X-ray diffraction and shows a 'zigzag-like' packing pattern due to S S intermolecular interaction. Structural features of these molecules are discussed by DFT quantum chemical calculations. (C) 2008 Elsevier B.V. All rights reserved

Synthetic and crystallographic studies of bicyclo[3.3.1]nonane derivatives: from strong to weak hydrogen bonds and the stereochemistry of network formation

The syntheses and crystal structures of four unsaturated bicyclo[3.3.1] nonane derivatives containing various functionalities are presented and their intermolecular interactions examined. The impact of unsaturation on crystal structures and intermolecular networks of the six membered rings was found to be significant compared to the saturated analogues. Thus, unsaturated diol rac-1, in striking contrast to its saturated analogue rac-6, does not crystallise with spontaneous resolution. The hydrogen bonds in the starting bicyclononane diene diol rac-1, and the weaker hydrogen bonds in the dienone rac-2, and the bromo and nitrile derivatives, rac-3, rac-4 and (+)-4, respectively, were found significant for the overall structure. The two bromine atoms in rac-3 have significant halogen-halogen interactions. In several structures 2D nets can be identified and overall structures can be interpreted as close packing of these layers. The crystal structures were also subject to independent analysis by Hirshfeld surfaces, and this method provided additional insights, especially for the structural role of the unsaturation. The possible relation between chiral networks and conglomerate formation is discussed

Chiral Lanthanum Metal-Organic Framework with Gated CO2 Sorption and Concerted Framework Flexibility br

A metal-organic framework (MOF)CTH-17based on lanthanum-(III) and the conformationally chiral linker 1,2,3,4,5,6-hexakis(4-carboxyphenyl)-benzene, cpb6-: [La2(cpb)]middot1.5dmf was prepared by the solvothermal method indimethylformamide (dmf) and characterized by variable-temperature X-raypowder diffraction (VTPXRD), variable-temperature X-ray single-crystal diffrac-tion (SCXRD), and thermogravimetric analysis (TGA).CTH-17is a rod-MOFwith new topologyoch. It has high-temperature stability with Sohncke spacegroupsP6122/P6522 at 90 K andP622 at 300 and 500 K, all phases characterizedwith SCXRD and at 293 K also with three-dimensional (3D) electron diffraction. VTPXRD indicates a third phase appearing after620 K and stable up to 770 K. Gas sorption isotherms with N2indicate a modest surface area of 231 m2g-1forCTH-17, roughly inagreement with the crystal structure. Carbon dioxide sorption reveals a gate-opening effect ofCTH-17where the structure opens upwhen the loading of CO2reaches approximately similar to 0.45 mmol g-1or 1 molecule per unit cell. Based on the SCXRD data, this isinterpreted asflexibility based on the concerted movements of the propeller-like hexatopic cpb linkers, the movementintramolecularly transmitted by the pi-pi stacking of the cpb linkers and helped by thefluidity of the LaO6coordination sphere. Thiswas corroborated by density functional theory (DFT) calculations yielding the chiral phase (P622) as the energy minimum and acompletely racemic phase (P6/mmm), with symmetric cpb linkers representing a saddle point in a racemization proces