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Hanhua Zhao Curtis P. Berlinguette John Bacsa Shane E. Tichy Kim R. Dunbar 《Journal of Cluster Science》2003,14(3):235-252
The preparation and characterization of two new mixed-valence, trinuclear species, [Mn3O(O2CCF3)6(H2O)3]CF3COOH4/3H2O (1) and [Mn3O(O2CCF3)6(CH3COOH)3] (2), is reported. Compound 1 crystallizes in the triclinic space group, P¯1 (No. 2), with the parameters, a=12.3131(9) Å, b=12.4427(9) Å, c=12.965(1) Å, =72.593(4)°, =73.453(5)°, =68.345(4)°, V=1727.2(2) Å3, and Z=2. A total of 14060 reflections were collected in the range 1.6827.52°. The final weighted and non-weighted agreement indices, R1=0.0589 and wR2=0.1445 were based on a total of 6953 unique reflections with an R
int value of 0.0542. Compound 2 crystallizes in the monoclinic space group, P21/n (No. 14), with the parameters, a=12.876(3) Å, b=12.212(4) Å, c=17.732(4) Å, =100.40(3)°, V=3640.4(1) Å3, and Z=4. A total of 32197 reflections were collected in the range 1.7227.13°. The final weighted and non-weighted agreement factors, R1=0.0647 and wR2=0.1609 were based on a total of 8018 unique reflections with an R
int
value of 0.0462. An investigation of the physical properties revealed that both compounds display an intermediate ground state of S=3/2 as a consequence of intramolecular antiferromagnetic coupling. The magnetic data for compound 1 was best fit to the parameters g=2.09, J=–5.5 cm–1, J=–3.4 cm–1, and D
Mn(III)=–4.5 cm–1; the data for compound 2 was best fit to the parameters g=2.10, J=–2.9 cm–1, J=–5.5 cm–1, and D
Mn(III)=–4.5 cm–1. 相似文献
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The aldol-type addition of 1,3-dibenzyl-dihydrouracil 2 to 2,3-O-isopropylidene-d-glyceraldehyde 3 was examined in different solvents and under Lewis acid catalysis in order to establish the stereochemical preferences. A stereodivergent synthesis of 5-trihydroxypropyl-dihydrouracil derivatives 4 and its C-5 epimer 5 was realized. The synthesis of ureido polyols 8 and 10 was obtained via the reductive ring opening of the templates 4 and 5. 相似文献
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The molecule of the title compound, C18H18O2, is a substituted cyclopropane ring. The electron density in this molecule has been determined by refining single‐crystal X‐ray data using scattering factors derived from quantum mechanical calculations. Topological analysis of the electron densities in the three cyclopropane C—C bonds was carried out. The results show the effects of this substitution on these C—C bonds. 相似文献
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John Bacsa Maurice Okello Pankaj Singh Vasu Nair 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(3):285-288
The conformation and tautomeric structure of (Z)‐4‐[5‐(2,6‐difluorobenzyl)‐1‐(2‐fluorobenzyl)‐2‐oxo‐1,2‐dihydropyridin‐3‐yl]‐4‐hydroxy‐2‐oxo‐N‐(2‐oxopyrrolidin‐1‐yl)but‐3‐enamide, C27H22F3N3O5, in the solid state has been resolved by single‐crystal X‐ray crystallography. The electron distribution in the molecule was evaluated by refinements with invarioms, aspherical scattering factors by the method of Dittrich et al. [Acta Cryst. (2005), A 61 , 314–320] that are based on the Hansen–Coppens multipole model [Hansen & Coppens (1978). Acta Cryst. A 34 , 909–921]. The β‐diketo portion of the molecule exists in the enol form. The enol –OH hydrogen forms a strong asymmetric hydrogen bond with the carbonyl O atom on the β‐C atom of the chain. Weak intramolecular hydrogen bonds exist between the weakly acidic α‐CH hydrogen of the keto–enol group and the pyridinone carbonyl O atom, and also between the hydrazine N—H group and the carbonyl group in the β‐position from the hydrazine N—H group. The electrostatic properties of the molecule were derived from the molecular charge density. The molecule is in a lengthened conformation and the rings of the two benzyl groups are nearly orthogonal. Results from a high‐field 1H and 13C NMR correlation spectroscopy study confirm that the same tautomer exists in solution as in the solid state. 相似文献
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Kyriakos C. Stylianou John Bacsa Darren Bradshaw Matthew J. Rosseinsky 《无机化学与普通化学杂志》2014,640(11):2123-2131
The reaction of NiII with a tetra‐benzoate pyrene ligand produces a 3D porous framework based on infinite 1D NiII chains. The NiII–O connectivity and the formation of a hydroxo‐bridge (μ3‐OH) responsible for the connection of the central NiII atoms within the 1D NiII–(μ3‐OH)2–NiII chains can be straightforwardly compared with the TiIV–O–TiIV connectivity seen in TiO2. The arrangement of the TBAPy ligand around the 1D rutile‐based chains leads in the generation of a porous framework with two distinct types of pores; based on the chemistries of these two types of pores, one can be labelled as hydrophobic and the other as hydrophilic. The use of different activation methods results in the generation of either a porous framework free of guest molecules or a completely solvent‐free material, in which the terminal H2O molecules bound to NiII were removed, leading thus to a framework with open NiII sites. CO2 isotherms collected on both frameworks at 195 K and one barshowed type I isotherms characteristic of microporous materials (BET surface areas for: guest‐free framework: 257(3) m2 · g–1; solvent‐free framework: 362(2) m2 · g–1). The affinity of both networks at zero coverage for both CO2 and CH4 was found to be greater when the unsaturated NiII sites are available within the void space. 相似文献
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Arumugam Thangavel Marika Wieliczko Christopher Scarborough Birger Dittrich John Bacsa 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(11):936-943
In the crystal structure of the title homoleptic CrII complex, [Cr(CH3CN)6](C24H20B)2·CH3CN, the [Cr(CH3CN)6]2+ cation is a high‐spin d4 complex with strong static, rather than dynamic, Jahn–Teller distortion. The electron density of the cation was determined by single‐crystal X‐ray refinements using aspherical structure factors from wavefunction calculations. The detailed picture of the electronic density allowed us to assess the extent and directionality of the Jahn–Teller distortion of the CrII cation away from idealized octahedral symmetry. The topological analysis of the aspherical d‐electron density about the CrII cation showed that there are significant valence charge concentrations along the axial Cr—N axes. Likewise, there were significant valence charge depletions about the CrII cation along the equatorial Cr—N bonds. These charge concentrations are in accordance with a Jahn–Teller‐distorted six‐coordinate complex. 相似文献
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Gerber I Oubenali M Bacsa R Durand J Gonçalves A Pereira MF Jolibois F Perrin L Poteau R Serp P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(41):11467-11477
The nitric acid oxidation of multiwalled carbon nanotubes leading to surface carboxylic groups has been investigated both experimentally and theoretically. The experimental results show that such a reaction involves the initial rapid formation of carbonyl groups, which are then transformed into phenol or carboxylic groups. At room temperature, this reaction takes place on the most reactive carbon atoms. At higher temperatures a different mechanism would operate, as evidenced by the difference in activation energies. Experimental data can be partially related to first-principles calculations, showing a multistep functionalization mechanism. The theoretical aspects of the present article have led us to propose the most efficient pathway leading to carboxylic acid functional groups on the surface. Starting from mono-vacancies, it ends up with the synergistic formation of dangling -COOH groups and the enlargement of the vacancies. 相似文献
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