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101.
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103.
Josué M. Silla Laize A.F. Andrade Matheus P. Freitas 《Magnetic resonance in chemistry : MRC》2019,57(7):373-379
The Perlin effect and its analog for fluorinated compounds (the fluorine Perlin-like effect) manifest on one-bond C─H (C─F for the fluorine Perlin-like effect) spin–spin coupling constants (SSCCs) in six-membered rings. These effects can be useful to probe the stereochemistry (axial or equatorial) of the C─H and C─F bonds, respectively. The origin of these effects has been debatable in the literature as being due to hyperconjugative interactions, dipolar effects, and induced current density. Accordingly, a variety of model compounds has been used to probe such effects since the cyclohexanone carbonyl group and the endocyclic heteroatom lone pairs play different roles on the above-mentioned effects. Thus, the 1JC─F SSCC in fluorinated lactams and lactones were theoretically studied to gain further insight on the nature of the fluorine Perlin-like effect. In addition, because the intramolecular α-effect has recently gained attention for its importance in the reactivity and stereoelectronic interactions in peroxide compounds, some fluorinated 1,2-dioxanes and 1,2-dithianes were studied to evaluate the role of the α-effect on the behavior of 1JC─F SSCCs. Differently from fluorinated ketones and ethers, the fluorine Perlin-like effect in the amides and esters cannot be explained by hyperconjugative or dipolar interactions alone, because the resonance in these groups affect the 1JC─F values. The O─O and S─S-containing systems exhibit a strong fluorine Perlin-like effect, but unlike the α-effect, this behavior cannot be explained neither by hyperconjugation nor by dipolar interactions alone; the spatial proximity of the C─F and O─O/S─S bonds is proposed to affect the magnitude of the 1JC─F SSCC. 相似文献
104.
Toke Meier Carlsen Søren Eilers Eduard Ortega Gunnar Restorff 《Journal of Mathematical Analysis and Applications》2019,469(2):1088-1110
We give conditions for when continuous orbit equivalence of one-sided shift spaces implies flow equivalence of the associated two-sided shift spaces. Using groupoid techniques, we prove that this is always the case for shifts of finite type. This generalises a result of Matsumoto and Matui from the irreducible to the general case. We also prove that a pair of one-sided shift spaces of finite type are continuously orbit equivalent if and only if their groupoids are isomorphic, and that the corresponding two-sided shifts are flow equivalent if and only if the groupoids are stably isomorphic. As applications we show that two finite directed graphs with no sinks and no sources are move equivalent if and only if the corresponding graph -algebras are stably isomorphic by a diagonal-preserving isomorphism (if and only if the corresponding Leavitt path algebras are stably isomorphic by a diagonal-preserving isomorphism), and that two topological Markov chains are flow equivalent if and only if there is a diagonal-preserving isomorphism between the stabilisations of the corresponding Cuntz–Krieger algebras (the latter generalises a result of Matsumoto and Matui about irreducible topological Markov chains with no isolated points to a result about general topological Markov chains). We also show that for general shift spaces, strongly continuous orbit equivalence implies two-sided conjugacy. 相似文献
105.
Electronic Structure Modulation in an Exceptionally Stable Non‐Heme Nitrosyl Iron(II) Spin‐Crossover Complex 下载免费PDF全文
Lucía Piñeiro‐López Dr. Norma Ortega‐Villar Prof. Dr. M. Carmen Muñoz Dr. Gábor Molnár Dr. Jordi Cirera Prof. Dr. Rafael Moreno‐Esparza Prof. Dr. Víctor M. Ugalde‐Saldívar Dr. Azzedine Bousseksou Prof. Dr. Eliseo Ruiz Prof. Dr. José A. Real 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(36):12741-12751
The highly stable nitrosyl iron(II) mononuclear complex [Fe(bztpen)(NO)](PF6)2 (bztpen=N‐benzyl‐N,N′,N′‐tris(2‐pyridylmethyl)ethylenediamine) displays an S=1/2?S=3/2 spin crossover (SCO) behavior (T1/2=370 K, ΔH=12.48 kJ mol?1, ΔS=33 J K?1 mol?1) stemming from strong magnetic coupling between the NO radical (S=1/2) and thermally interconverted (S=0?S=2) ferrous spin states. The crystal structure of this robust complex has been investigated in the temperature range 120–420 K affording a detailed picture of how the electronic distribution of the t2g–eg orbitals modulates the structure of the {FeNO}7 bond, providing valuable magneto–structural and spectroscopic correlations and DFT analysis. 相似文献
106.
Humberto E. Ortega João M. Batista Weilan G.P. Melo Jon Clardy Mônica T. Pupo 《Tetrahedron letters》2018,59(13):1239
The known antibiotic and cytotoxic compounds griseorhodin A (1) and griseorhodin C (2) were produced in solid culture by Streptomyces puniceus AB10, which was isolated from the leaf-cutter ant Acromyrmex rugosus rugosus. Their absolute configurations were unambiguously established as 6S,6aS,7S,8S and 6R,6aS,7S,8R, respectively, using vibrational circular dichroism (VCD) and density functional theory (DFT) calculations. 相似文献
107.
Iraís A. Quintero‐Ortega Gabriel Jaramillo‐Soto Pedro R. García‐Morán M. Luz Castellanos‐Cárdenas Gabriel Luna‐Bárcenas Eduardo Vivaldo‐Lima 《大分子反应工程》2008,2(4):304-320
A comparison of kinetic models for dispersion polymerization of MMA and styrene in supercritical CO2 is presented. The limiting case of solution polymerization, as a simplified case, was also addressed. Calculation of the partition of components between the continuous and dispersed phases was emphasized. Experimental data for the solution and dispersion polymerizations of styrene and MMA, using different types of stabilizers, were used to guide the study. Although all the models analyzed can be considered as “adequate” in representing the behavior of the system, some of their strengths and drawbacks have been highlighted.
108.
Rodríguez-Pulido A Ortega F Llorca O Aicart E Junquera E 《The journal of physical chemistry. B》2008,112(39):12555-12565
A 1:1 mixture of the cationic lipid 3beta-[ N-( N', N'-dimethylaminoethane)-carbamoyl]cholesterol hydrochloride (DC-Chol) and the zwitterionic lipid, 1,2-dioleoyl- sn-glycero-3-phosphoetanolamine (DOPE), has been used to compact calf-thymus DNA (CT-DNA) in aqueous buffered solution at 298.15 K. The formation process of this lipoplex has been analyzed by means of electrophoretic mobility, cryo-TEM, dynamic light scattering, and fluorescence spectroscopy techniques. The experimental results indicate that DC-Chol/DOPE liposomes are mostly spherical and unilamellar, with a mean diameter of around 99 +/- 10 nm and a bilayer with a thickness of 4.5 +/- 0.5 nm. In the presence of CT-DNA, DC-Chol/DOPE/CT-DNA lipoplexes are formed by means of a strong entropically driven surface electrostatic interaction, as confirmed by zeta potential and fluorescence results, as a consequence of which DNA is compacted and condensed at the surface of the cationic liposomes. The negative charges of DNA phosphate groups are neutralized by the positive charges of cationic liposomes at the isoneutrality L/ D ratio, ( L/ D) varphi around 4, obtained from electrophoretic, fluorescence, and DLS measurements. The decrease in the fluorescence emission intensity of ethidium bromide, EtBr, initially intercalated between DNA base pairs, as long as the association between the biopolymer and the cationic liposomes takes place has permitted one to confirm its electrostatic character as well as to evaluate the different microenvironments of varying polarity of DNA-double helix, liposomes, and/or lipoplexes. Electronic microscopy reveals a rich scenario of possible nanostructures and morphologies for the lipoplexes, from unilamellar DNA-coated liposomes to multilamellar lipoplexes passing through cluster-like structures and several intermediate morphologies. 相似文献
109.
110.
Thawan G. Oliveira Berlane G. Santos Josué M. Gonçalves Lucio Angnes 《Electroanalysis》2023,35(9):e202200441
This work describes the development of a fast, precise and reliable voltammetric method for the quantification of indapamide, an orally active diuretic sulfonamide used for hypertensive treatment. This compound acts inhibiting sodium reabsorption and increasing the elimination of water. This characteristic was responsible for its banishment by the International Olympic Committee since 1999. The study begins by finding an adequate potential range (−0.20 to 0.30 V) to avoid poisoning the working glassy carbon electrode (GCE) in phosphate buffer 0.10 mol L−1 (pH=12.0). Utilizing flow injection analysis, linear responses between 2.0 × 10−6 mol L−1 to 2.5 × 10−5 mol L−1 of indapamide (R2=0.995), and detection limit (LOD) 3.0 × 10−7 mol L−1 were obtained. This method was applied for the quantification of indapamide in tablets and in synthetic urine. The same flow system was used for the analysis of commercial drugs and the response obtained corresponded to 98 % of the concentration indicated on the drug label. These tablets were also analyzed by high performance liquid chromatography (HPLC), obtaining a recovery of 103 % and LOD 4.0 × 10−7 mol L−1. The velocity of analysis using flow methods compares advantageously to the classical chromatographic methods. For synthetic urine, linear responses were obtained in samples spiked in the region from 5.0 × 10−6 mol L−1 to 30 × 10−6 mol L−1 (R2=0.991) and LOD 3.0 × 10−7 mol L−1. 相似文献