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101.
Comparison of halogen bonding and van der Waals and π–π interactions in 4,5‐dibromo‐2‐hexyloxyphenol
Fabio D. Cukiernik Florencia Cecchi Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(5):o233-o236
The title compound, C12H16BrO2, is an interesting case of a simple organic molecule making use of five different types of intra‐ and intermolecular interactions (viz. conventional and nonconventional hydrogen bonds, and π–π, Br...Br and Br...O contacts), all of them relevant in the molecular and crystal structure geometry. The molecules are strictly planar, with an intramolecular O—H...O hydrogen bond, and associate into two‐dimensional structures parallel to (01) through two different types of halogen bonding. The planar structures, in turn, stack parallel to each other interlinked by C—H...π and π–π contacts. Also discussed are the relevant structural features leading to the rather low melting point of the compound. 相似文献
102.
Vieira EF Cestari AR de Santos EB Rezende CX 《Journal of colloid and interface science》2006,298(1):74-78
Isothermal calorimetry was used to determine enthalpy changes for interaction of divalent cobalt, nickel, copper, and zinc chlorides with silica gel functionalized with vanillin, Sil-Van. The thermal effect, Q(int), and the corresponding amount of cation that interacts, n(int), were obtained in the same experiment. Langmuir expressions for adsorption isotherms were applied to determine the maximum adsorption capacity to form a monolayer, N(mon), and the energy of interaction for a saturated monolayer per gram of Sil-Van, Q(mon). From knowledge of N(mon) and Q(mon), the molar enthalpy of interaction for formation of a monolayer of anchored cations per gram of Sil-Van, Delta(mon)H(m), was determined. Interactions between the Lewis-acidic cations and the donor atom attached to silica are reflected by Delta(mon)Hm values in the order Ni2+ > Cu2+ > Zn2+ congruent with Co2+. 相似文献
103.
Synthesis of niobia nanocrystals with controlled morphology 总被引:1,自引:0,他引:1
In this work, TT niobia-phase nanocrystals with controlled morphology were obtained by the hydrothermal treatment of a niobium peroxo complex precursor at very low temperatures. The materials obtained by this route presented a very high surface area (ranging from 79 to 327 m(2)/g), disordered NbO(6), NbO(7), and NbO(8) polyhedra, Nb-O superficial sites, and a superficial OH group, which must have ensured the acidic characteristics of this oxide. 相似文献
104.
Dalmora SL Júnior LB Schmidt CA Vaccari SF Oliveira PR Codevilla CF 《Journal of AOAC International》2004,87(6):1305-1308
Enoxaparin is a low-molecular weight heparin used clinically for the prevention and treatment of venous and arterial thrombosis. An anti-factor Xa assay was used to evaluate the potency of the final drug preparation. Method validation investigated parameters such as the range, linearity (r2 = 0.9971), precision, accuracy, and robustness; the biological assay incorporated a chromogenic endpoint and detection at 405 nm. The method yielded good results with a quantitation limit of 0.037 IU/mL and a detection limit of 0.011 IU/mL. The results demonstrated the validity of the anti-factor Xa assay for the determination of enoxaparin. 相似文献
105.
Quintella CM Lima AM Gonçalves CC Watanabe YN Mammana AP Schreiner MA Pepe I Pizzo AA 《Journal of colloid and interface science》2003,262(1):221-226
Interfacial interactions control two processes empirically known to be critical for molecular anchoring in twisted nematic liquid crystal displays technology (TN-LCDs): surface treatment and filling procedure. Static and dynamical interfacial tensions (Gamma(SL)) between liquids and several substrates with similar roughness were observed respectively by contact angle (theta(c)) of sessile drops and by fluorescence depolarization of thin liquid films flowing at high velocity. Gamma(SL) decreased when glass was coated with tin dioxide and increased with polyvinyl alcohol (PVA) deposition. Drops were circular for all substrates except rubbed PVA, where they flowed spontaneously along the rubbing direction, reaching an oblong form that had theta(c) parallel and perpendicular to the rubbing direction respectively greater and smaller than theta(c) for non-rubbed PVA. This is attributed to polar group alignment generating an asymmetric Gamma(SL) distribution with nanometric preferential direction, inducing a capillary-like flow. Polarization and anisotropy maps for high-velocity flow parallel to the PVA rubbing direction showed an increase in the net alignment of molecular domains and a widening of the region where it occurred. This is attributed to preferential anchoring in the downstream direction, instead of in several directions, as for non-rubbed PVA. This explains why filling direction is crucial for TN-LCDs homogeneous behavior. 相似文献
106.
Schubert A Werle AL Schmidt CA Codevilla C Bajerski L Chiappa R Cardoso SG 《Journal of AOAC International》2003,86(3):501-504
An accurate, simple, reproducible, and sensitive liquid chromatographic method was developed and validated for the determination of omeprazole in powder for injection and in pellets. The analyses were performed at room temperature on a reversed-phase C18 column of 250 x 4.6 mm id, 5 microm particle size. The mobile phase, composed of methanol-water (90 + 10, v/v), was pumped at a constant flow rate of 1.5 mL/min. Detection was performed on a UV detector at 301 nm. The method was validated in terms of linearity, precision, accuracy, and ruggedness. The response was linear in the range 32-48 microg/mL (r2 = 0.9976). The relative standard deviation values for intra- and interday precision studies were 1.22 and 1.56% for injectable and 2.13 and 2.45% for pellets, respectively. Recoveries ranged between 95.81 and 100.48%. 相似文献
107.
Justi KC Fávere VT Laranjeira MC Neves A Peralta RA 《Journal of colloid and interface science》2005,291(2):369-374
Chitosan biopolymer chemically modified with the complexation agent 2[-bis-(pyridylmethyl)aminomethyl]-4-methyl-6-formylphenol (BPMAMF) was employed to study the kinetics and the equilibrium adsorption of Cu(II), Cd(II), and Ni(II) metal ions as functions of the pH solution. The maximum adsorption of Cu(II) was found at pH 6.0, while the Cd(II) and Ni(II) maximum adsorption occurred in acidic media, at pH 2.0 and 3.0, respectively. The kinetics was evaluated utilizing the pseudo-first-order and pseudo-second-order equation models and the equilibrium data were analyzed by Langmuir and Freundlich isotherms models. The adsorption kinetics follows the mechanism of the pseudo-second-order equation for all studied systems and this mechanism suggests that the adsorption rate of metal ions by CHS-BPMAMF depends on the number of ions on the adsorbent surface, as well as on their number at equilibrium. The best interpretation for the equilibrium data was given by the Langmuir isotherm and the maximum adsorption capacities were 109 mg g-1 for Cu(II), 38.5 mg g-1 for Cd(II), and 9.6 mg g-1 for Ni(II). The obtained results show that chitosan modified with BPMAMF ligand presented higher adsorption capacity for Cu(II) in all studied pH ranges. 相似文献
108.
R. Baggio O. González M. T. Garland J. Manzur V. Acuña A. M. Atria E. Spodine O. Peña 《Journal of chemical crystallography》1993,23(9):749-753
The title compound, Cu2C17H16O2.5Cl2, is a copper(II) complex, in which each dimeric unit has two copper atoms bridged by a pyrazolato ligand, a di(2-pyridyl)]methane ligand, and an oxygen atom from the modified methylene group that links the two pyridine rings (O-C-O-CH2CH3). The complex crystallizes in the monoclinic groupP21/n,a=7.7330(1),b=19.589(6),c=13.123(2)Å,=95.020(0)°,V=1980.3(7)Å3,Z=4,F
w=514.3,D
Do
=1.725 g cm–3(MoK)=0.71073 Å,F(000)=1032,=2.44 mm–1, R=0.044 for 2209 observed reflections,Rw=0.047,s=0.086. Each dimer is linked to the next unit by long chlorine bonds (Cu(2)-Cl(1)=2.846(2)Å). These tetrameric units form zigzagged chains through copperchlorine bonds of 3.380(2)Å. The copper(II) complex presents antiferromagnetic behavior withT
m=161 K. 相似文献
109.
Ricardo Baggio M. Virginia Remedi María Teresa Garland Elba I. Buján 《Journal of chemical crystallography》1997,27(9):499-505
The crystal structure of 1-pyrrolidino-2,4,6-trinitrobenzene3, 1-morpholino-2,4,6-trinitrobenzene4 and 1-piperidino-2,4,6-trinitrobenzene5 have been determined by single-crystal X-ray diffraction data and the structure in solution was investigated by UV-visible spectrophotometry and13C nmr. The three compounds are monoclinic, space groupP2i/n. Unit cell dimensions area=6.6660(1),b=8.612(1),c=20.696(3) Å, β=90.73(1)o, andD c =1.58 g cm?3 for compound3;a=7.090(2),b=21.493(9),c=8.298(3) Å, β=101.27(1)o, andD c 1.60 g cm?3 for compound4 anda=10.426(1),b=10.038(1),c=12.291(1) Å, β=90.04(1)o withD c =1.53 g cm?3 for compound5 forZ=4. In the solid state, differences regarding the planarity of the aromatic ring in the three substrates were found. Rotation of theortho-nitro groups and of the amino group out of the aromatic plane was observed both in the solid state and in the solution. Greater coplanarity of the two rings was found in3 than in4 and5. 相似文献
110.
An X-ray crystallographic study of 2,5-dimethyl-3,4-diacetylpyrrole showed that the crystals are monoclinic, space groupP21/n,a = 10·01(3),b = 12·93(3),c = 7·41(2) Å and = 91·5(5) °. The crystal structure was solved by direct methods and refined by least squares to a finalR factor of 0·13. The values determined for the bond distances and angles of the pyrrole ring are in good agreement with the values reported in the literature. However, there are significant changes in the exocyclic bond angles of the atoms of the ring. The planes of the acetyl groups are tilted with respect to the ring plane, forming dihedral angles of 22 ° and 40 °. 相似文献