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991.
Lapointe D Markiewicz T Whipp CJ Toderian A Fagnou K 《The Journal of organic chemistry》2011,76(3):749-759
The challenge of achieving selective and predictable functionalizations at C-H bonds with complex poly(hetero)aromatic substrates was addressed by two different approaches. Site-selectivity can be obtained by applying various reaction conditions that are (hetero)arene specific to substrates that contain indoles, pyridine N-oxide, and polyfluorinated benzenes. An experimental classification of electron-rich heteroarenes based on their reactivity toward palladium-catalyzed C-H functionalization was established, the result of which correlated well with the order of reactivity predicted by the DFT-calculated concerted metalation-deprotonation (CMD) pathway. Model substrates containing two reactive heteroarenes were then reacted under general reaction conditions to demonstrate the applicability this reactivity chart in predicting the regioselectivity of the palladium-catalyzed direct arylation and benzylation reactions. 相似文献
992.
ó Proinsias K Giedyk M Loska R Chromiński M Gryko D 《The Journal of organic chemistry》2011,76(16):6806-6812
The acid-sensitivity of vitamin B(12) derived mono- and diamides was studied. It was found that the use of reductive ring-opening of the lactone moiety deactivated undesired decomposition of c-mono- and c,d-diamides under acidic conditions. As a result, reactions gave respectively c- or d-acids which were further functionalized via coupling with amino acids. Though mono- and diamides exhibited acid sensitivity, they were used for the preparation of several highly functionalized molecules showing their stability under various reaction conditions. 相似文献
993.
Pritha Talukder Shyamapada ShitAshok Sasmal Stuart R. BattenBoujemaa Moubaraki Keith S. MurraySamiran Mitra 《Polyhedron》2011,30(11):1767-1773
A novel hexanuclear complex [{(CuL)2Cu}2(μ-dca)2](ClO4)2·2L′(1) (where H2L = (OH)C6H4C(CH3)N(CH2)3NC(CH3)C6H4(OH) or N,N′-bis(2-hydroxyacetophenone) propylenediimine and dca = N(CN)2− and L′ = 2-hydroxyacetophenone) has been synthesized and characterized by elemental analysis, UV-Vis, FT-IR spectroscopic and electrochemical methods. Single crystal X-ray structural characterization reveals a centrosymmetric nature of the complex unit, where the metal centers adopt distorted square-planar and distorted octahedral geometries. Structural analysis also reveals μ2-phenoxo bridges between terminal and the central copper(II) centers of the asymmetric [(CuL)2Cu(dca)] unit, the latter being interconnected to its symmetry related counterpart by double μ1,5-dca bridges, leading to the hexanuclear complex ion [{(CuL)2Cu}2(μ-dca)2]2+. Low temperature susceptibility measurements of 1 revealed the presence of strong antiferromagnetic coupling (2J = −407 cm−1) between the copper(II) centers. 相似文献
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997.
Adsorptive behavior of CO2, CH4 and their mixtures in carbon nanospace: a molecular simulation study
Palmer JC Moore JD Roussel TJ Brennan JK Gubbins KE 《Physical chemistry chemical physics : PCCP》2011,13(9):3985-3996
Using molecular simulation, four types of nanoporous carbons are examined as adsorbents for the separation of CO(2)/CH(4) mixtures at ambient temperature and pressures up to 10 MPa. First, the adsorption selectivity of CO(2) is investigated in carbon slit pores and single-walled carbon nanotube bundles in order to find the optimal pore dimensions for CO(2) separation. Then, the adsorptive properties of the optimized slit pore and nanotube bundle are compared with two realistic nanoporous carbon models: a carbon replica of zeolite Y and an amorphous carbon. For the four carbon models, adsorption isotherms and isosteric heats of adsorption are presented for both pure components and mixtures. Special attention is given to the calculation of excess isotherms and isosteric heats, which are necessary to assess the performance of model nanoporous materials in the context of experimental measurements. From these results, we discuss the impact that variables such as pore size, pore morphology, pressure and mixture composition have on the performance of nanoporous carbons for CO(2) separation. 相似文献
998.
Ryan KR Ramirez-Cuesta AJ Refson K Jones MO Edwards PP David WI 《Physical chemistry chemical physics : PCCP》2011,13(26):12249-12253
A combination of inelastic neutron scattering (INS) spectroscopy and Raman spectroscopy with periodic density functional theory calculations is used to provide a complete assignment of the vibrational spectra of α-lithium amidoborane (α-LiNH(2)BH(3)). The Born charge density and the atomic motion up to the decomposition temperature have been modelled. These models not only explain the nature of bonding in α-LiNH(2)BH(3) but also provide an insight into the atomic mechanisms of its decomposition. The (INS) measurements were performed in the range of 0-4000 cm(-1) on the high-resolution time-of-flight TOSCA INS spectrometer at the ISIS Spallation Neutron Source at the Rutherford Appleton Laboratory. 相似文献
999.
Spin crossover in di-, tri- and tetranuclear, mixed-ligand tris(pyrazolyl)methane iron(II) complexes
Schneider CJ Moubaraki B Cashion JD Turner DR Leita BA Batten SR Murray KS 《Dalton transactions (Cambridge, England : 2003)》2011,40(26):6939-6951
A series of polynuclear mixed-ligand tris(pyrazolyl)methane iron(II) complexes displaying high temperature spin crossover behaviour has been synthesised. These complexes are of the type [(Fe((3,5-Me(2)pz)(3)CH))(n)(μ-L)](BF(4))(2n), where μ-L is one of five bridging ligands X(CH(2)OCH(2)C(pz)(3))(n), (X = the central linking moiety, pz = pyrazolyl ring and n = 2 (ditopic), 3 (tritopic) or 4 (tetratopic)). Throughout the series the terminal tris(3,5-dimethylpyrazolyl)methane co-ligand (3,5-Me(2)pz)(3)CH and the BF(4)(-) counter anion were kept constant while variations in the central linking moiety have produced three dinuclear complexes and a trinuclear and tetranuclear complex, all isolated as solvates. The three dinuclear complexes are a 1,4-xylene-bridged complex 1·2DME, a 2,6-naphthalene-bridged complex 2·2.5MeCN.2DME and a 1,4-butene-bridged complex 3·2DME. The trinuclear complex 4·solvent (solvent undefined) has a 1,3,5-mesitylene core and the tetranuclear complex, 5·8MeCN.2(t)BuOMe, has a 1,2,4,5-tetramethylbenzene core (DME = dimethoxyethane, (t)BuOMe = tertiarybutyl-methylether). The trinuclear cluster has a "3-up" cup shape with the cups arranging themselves in pairs to form capsules that contain anion guests. All the solvated compounds have been structurally characterised and both the solvated and desolvated versions have had their magnetic and thermal properties thoroughly investigated by variable temperature magnetic susceptibility, differential scanning calorimetric and M?ssbauer spectral methods. They all display typical low spin iron(II) magnetic behaviour at room temperature and all undergo a spin state transition to high spin iron(II) above room temperature. In particular, complex 1·2DME shows an abrupt spin transition which shifts, upon desolvation, to a lower value of T(1/2) and in addition displays a small thermal hysteresis. 相似文献
1000.
Ross TM Moubaraki B Wallwork KS Batten SR Murray KS 《Dalton transactions (Cambridge, England : 2003)》2011,40(39):10147-10155
The new dipyridylamino/triazine ligand DDE (N(2),N(2),N(4),N(4)-tetraethyl-N(6),N(6)-di(pyridin-2-yl)-1,3,5-triazine-2,4,6-triamine) has been incorporated into the mononuclear Fe(II) SCO compounds cis-[Fe(II)(NCSe)(2)(DDE)(2)] (1), cis-[Fe(II)(NCBH(3))(2)(DDE)(2)] (2), and cis-[Fe(II)(NCS)(2)(DDE)(2)] (3). Magnetic susceptibility measurements reveal that each of 1, 2 and 3 undergoes a complete, continuous spin transition with a T(?) of ~260 K, ~300 K and ~205 K, respectively. An analogue and isomorph of 1, cis-[Co(II)(NCSe)(2)(DDE)(2)] (4), remains high spin down to low temperatures. Variable temperature single crystal data reveal that 1 and 4 undergo a crystallographic phase transition (from orthorhombic Pbcn at high temperatures to monoclinic P2/c at low temperatures) accompanied by an order-disorder transition of ethyl moieties of the DDE ligand. In the Pbcn phase, the structures of 1 and 4 contain one crystallographically unique M(II) centre, while in the P2/c phase, 1 and 4 contain two crystallographically unique M(II) centres. Variable temperature powder X-ray diffraction experiments reveal that the crystallographic phase transition occurs at ~250 K for 1. The occurrence of the concomitant order-disorder and crystallographic phase transitions undergone by 1 and 4 is not directly apparent in their magnetic susceptibility measurements, and this is likely due to the local environment of the M(II) centres remaining largely undisturbed as the transitions occur. The compound 2 is isostructural to 1 and 4 at low temperatures. 相似文献