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1.
Söhnel T Brown R Kloo L Schwerdtfeger P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(14):3167-3173
The stability of gold iodides in the oxidation state +I and +III is investigated at the ab initio and density functional level using relativistic and nonrelativistic energy-adjusted pseudopotentials for gold and iodine. The calculations reveal that relativistic effects stabilize the higher oxidation state of gold as expected, that is Au2I6 is thermodynamically stable at the relativistic level, whilst at the nonrelativistic level the complex of two iodine molecules weakly bound to both gold atoms in Au2I2 is energetically preferred. The rather low stability of AuI3 with respect to dissociation into AuI and I2 will make it difficult to isolate this species in the solid state as (possibly) Au2I6 or detect it by matrix-isolation techniques. The monomer AuI3 is Jahn-Teller distorted from the ideal trigonal planar (D3h) form, but adopts a Y-shaped structure (in contrast to AuF3 and AuCl3), and in the nonrelativistic case can be described as I2 weakly bound to AuI. Relativistic effects turn AuI3 from a static Jahn-Teller system to a dynamic one. For the yet undetected gas-phase species AuI accurate coupled-cluster calculations for the potential energy curve are used to predict vibrational-rotational constants. Solid-state density functional calculations are performed for AuI and Au2I6 in order to predict cohesive energies. 相似文献
2.
Modern solid state NMR techniques and concepts in structural studies of synthetic polymers
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In this mini‐review, we present the solid state nuclear magnetic resonance (NMR) methods which trace the new tendency in structural studies of synthetic polymers. The review is organized into three sections. In the first part, short theoretical background and introduction to very fast magic angle spinning NMR technique with sample rotation 60 kHz are shown. The second part presents method for enhancing the sensitivity of NMR experiments by application of dynamic nuclear polarization magic angle spinning technique. In the third section, the power of the NMR crystallography approach which can be used for fine refinement of polymers structure on the atomic level is discussed. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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The polychelates of Ti(III), VO(IV), Cr(III), Mn(III), Fe(III), Zr(IV), MoO2(VI) and UO2(VI) with the chelating hydrazone derived from 2,4-dihydroxy-5-acetylacetophenone and carbohydrazide have been synthesized.
The polychelates have been characterized on the basis of elemental analyses, IR, magnetic moment, electronic spectral data
and thermal analysis. Various kinetic parameters have been determined from the thermal data and decomposition follows first
order kinetics. The solid—state electrical conductivity has been measured over 40–130°C-temperature range and all the compounds
showed semiconducting behavior as their conductivity increases with increase in temperature. The ligand and its polychelates
have also been screened for their antimicrobial activities using various microorganisms and all of them were found to be active
against the organisms. 相似文献
4.
Digianantonio KM Glover SA Johns JP Rosser AA 《Organic & biomolecular chemistry》2011,9(11):4116-4126
N,N-dialkoxyamides 1c, a virtually unstudied member of the new class of anomeric amides, amides bearing two electronegative atoms at nitrogen, have been synthesised in useful yields directly from hydroxamic esters using phenyliodine(III)bis(trifluoroacetate) (PIFA). Infrared carbonyl stretch frequencies and carbonyl (13)C NMR properties have been reported, which support strong inhibition of amide resonance in these amides. Their thermal decomposition reactions in mesitylene at 155 °C proceed by homolysis to form alkoxyamidyl and alkoxyl free radicals in preference to HERON rearrangements to esters. The reactions follow first-order kinetics and for a series of N,N-dimethoxy-4-substituted benzamides, activation energies of 125-135 kJ mol(-1) have been determined together with weakly negative entropies of activation. 相似文献
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W. P. Pawlowski S. S. Sankar R. D. Gilbert R. E. Fornes 《Journal of polymer science. Part A, Polymer chemistry》1987,25(12):3355-3362
Several cellulose derivatives were synthesized and characterized by IR and 1H-NMR spectroscopy. The positions of substitution in these derivatives were confirmed using solid state 13C-NMR spectroscopy techniques. 相似文献
7.
V. V. Nedel’ko B. L. Korsunskii N. N. Makhova N. V. Chukanov T. S. Larikova I. V. Ovchinnikov V. A. Tartakovsky 《Russian Chemical Bulletin》2009,58(10):2028-2034
1,3,3-Trinitroazetidine (TNAZ) was synthesized using the alternative approach based on the transformation of 3-oximino-1-(p-toluenesulfonyl)azetidine in the reaction with nitric acid through intermediate pseudonitrol. The thermal decomposition of TNAZ in the gas phase, melt and m-dinitrobenzene solution in a wide concentration range (5–80%) was studied by manometry, volumetry, thermogravimetry, IR spectroscopy, and mass spectrometry. In the gas phase in the temperature range from 170 to 220°C the thermal decomposition proceeds according to the first-order kinetic law with the activation energy 40.5 kcal mol?1 and pre-exponential factor 1015.0 s?1. The major gaseous reaction products are N2, NO, NO2, CO2, H2O, and nitroacetaldehyde, and trace amounts of CO and HCN are formed. The rate-determining step of the process is the homolytic cleavage of the N-NO2 bond in the TNAZ molecule. In melt at 170–210 °C the thermal decomposition proceeds with the pronounced self-acceleration and the maximum reaction rates are observed at conversions 53.9–67.4%. The solid decomposition products accelerate the reaction. It is most likely that the autocatalysis of TNAZ decomposition in the liquid phase is due to the autocatalytic decomposition of 1-nitroso-3,3-dinitroazetidine, which is formed by the thermal decomposition of TNAZ. In m-dinitrobenzene TNAZ also decomposes with self-acceleration. The higher the concentration in the solution, the more pronounced the self-acceleration. Additives of picric acid moderately accelerate the thermal decomposition of TNAZ, whereas hexamethylenetetraamine additives exert a strong acceleration. 相似文献
8.
Kinetics of solid state thermal decomposition reactions 总被引:1,自引:0,他引:1
K. N. Ninan 《Journal of Thermal Analysis and Calorimetry》1989,35(4):1267-1278
The author wishes to thank Prof. C. G. R. Nair, Dr. V. R. Gowarikar, Mr. M. R. Kurup and Dr. K. V. C. Rao for their encouragements. Thanks are due to Prof. P. M. Madhusudanan and Dr. K. Krishnan for helpful discussions and to Director, VSSC for the kind permission to publish this work. 相似文献
9.
Dávalos JZ Herrero R Chana A Guerrero A Jiménez P Santiuste JM 《The journal of physical chemistry. A》2012,116(9):2261-2267
We have studied the energetics and structural properties of trans-cinnamic acid (CA), o-, m-, and p-coumaric acids (2-, 3-, and 4-hydroxycinnamic acids), caffeic acid (3,4-dihydroxycinnamic acid), ferulic acid (4-hydroxy-3-methoxycinnamic acid), iso-ferulic acid (3-hydroxy-4-methoxycinnamic acid), and sinapic acid (3,5-dimethoxy-4-hydroxycinnamic acid). The experimental values of Δ(f)H(m)°(g), determined (in kJ·mol(-1)) for CA (-229.8 ± 1.9), p-coumaric acid (-408.0 ± 4.4), caffeic acid (-580.0 ± 5.9), and ferulic acid (-566.4 ± 5.7), allowed us to derive Δ(f)H(m)°(g) of o-coumaric acid (-405.6 ± 4.4), m-coumaric acid (-406.4 ± 4.4), iso-ferulic acid (-565.2 ± 5.7), and sinapic acid (-698.8 ± 4.1). From these values and by use of isodesmic/homodesmotic reactions, we studied the energetic effects of π-donor substituents (-OH and -OCH(3)) in cinnamic acid derivatives and in the respective benzene analogues. Our results indicate that the interaction between -OCH(3) and/or -OH groups in hydroxycinnamic acids takes place without significant influence of the propenoic fragment. 相似文献
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The reaction system (NH4)3VS4/CuCl/PPh3/Et4NBr afforded a series of [VS4-Cun] dusters with various core configurations in the solid state at low heating temperature. The structural regularity of [VS4-Cun] dusters and the influence of the CuCl:(NH4)3VS4 ratio as well as that of reaction temperature and time on the formation of duster core have been summarized. The reaction mechanism of forming V-Cu-S clusters has also been explored. 相似文献
12.
Christine B. BaltusNeil J. Press Milan D. AntonijevicGraham J. Tizzard Simon J. ColesJohn Spencer 《Tetrahedron》2012,68(45):9272-9277
A biphenyl library incorporating amide and sulfonamide groups has been synthesised via microwave-mediated Suzuki-Miyaura couplings. Many derivatives were crystallised from dichloromethane/methanol and analysed by single crystal X-ray diffraction. An interesting structure was obtained for N-(4′-methylbiphenyl-4-yl)acetamide with Z′=6 and hydrogen-bonding networks of the type N-H…O in the unit cell. 相似文献
13.
Unusual regularities are observed for decomposition of dinitramide metal salts in the solid phase: the solid-phase reaction
is 10–103 times faster than that in the melt, its rate has a sharp peak in the region of eutectics melting with the decomposition product
(metal nitrate), and it is instantly inhibited by water vapor. In the inhibited regime, the rate in the solid phase is lower
than that in the liquid phase. No indications of this anomalous behavior are observed for the decomposition of the dinitramide
guanidinium salt.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1947–1950, November, 1997. 相似文献
14.
Barchi JJ Karki RG Nicklaus MC Siddiqui MA George C Mikhailopulo IA Marquez VE 《Journal of the American Chemical Society》2008,130(28):9048-9057
The conformations of three 2',3'-difluoro uridine nucleosides were studied by X-ray crystallography, NMR spectroscopy, and ab initio calculations in an attempt to define the roles that the two vicinal fluorine atoms play in the puckering preferences of the furanose ring. Two of the compounds examined contained fluorine atoms in either the arabino or xylo dispositions at C2' and C3' of a 2',3'-dideoxyuridine system. The third compound also incorporated fluorine atoms in the xylo configuration on the furanose ring but was substituted with a 6-azauracil base in place of uracil. A battery of NMR experiments in D 2O solution was used to identify conformational preferences primarily from coupling constant and NOE data. Both (1)H and (19)F NMR data were used to ascertain the preferred sugar pucker of the furanose ring through the use of the program PSEUROT. Compound-dependent parameters used in the PSEUROT calculations were newly derived from complete sets of conformations calculated from high-level ab initio methods. The solution and theoretical data were compared to the conformations of each molecule in the solid state. It was shown that both gauche and antiperiplanar effects may be operative to maintain a pseudodiaxial arrangement of the C2' and C3' vicinal fluorine atoms. These data, along with previously reported data by us and others concerning monofluorinated nucleoside conformations, were used to propose a model of how fluorine influences different aspects of nucleoside conformations. 相似文献
15.
Stowe AC Shaw WJ Linehan JC Schmid B Autrey T 《Physical chemistry chemical physics : PCCP》2007,9(15):1831-1836
The mechanism of hydrogen release from solid state ammonia borane (AB) has been investigated via in situ solid state (11)B and (11)B{(1)H} MAS-NMR techniques in external fields of 7.1 T and 18.8 T at a decomposition temperature of 88 degrees C, well below the reported melting point. The decomposition of AB is well described by an induction, nucleation and growth mechanistic pathway. During the induction period, little hydrogen is released from AB; however, a new species identified as a mobile phase of AB is observed in the (11)B NMR spectra. Subsequent to induction, at reaction times when hydrogen is initially being released, three additional species are observed: the diammoniate of diborane (DADB), [(NH(3))(2)BH(2)](+)[BH(4)](-), and two BH(2)N(2) species believed to be the linear (NH(3)BH(2)NH(2)BH(3)) and cyclic dimer (NH(2)BH(2))(2) of aminoborane. At longer reaction times the sharper features are replaced by broad, structureless peaks of a complex polymeric aminoborane (PAB) containing both BH(2)N(2) and BHN(3) species. The following mechanistic model for the induction, nucleation and growth for AB decomposition leading to formation of hydrogen is proposed: (i) an induction period that yields a mobile phase of AB caused by disruption of the dihydrogen bonds; (ii) nucleation that yields reactive DADB from the mobile AB; and (iii) growth that includes a bimolecular reaction between DADB and AB to release the stored hydrogen. 相似文献
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Reported are the syntheses and the crystallographic characterization of two structurally related solid-state compounds: (Eu(1-x)Ca(x))(2)Ge(2)Pb (space group Pbam) and (Sr(x)Eu(1-x))(2)Ge(2)Pb (space group Cmmm). Both structures boast anionic sublattices with fully ordered Ge and Pb at the atomic level, which is unusual for elements of the same group. Despite the nearly identical formulas and the similar chemical makeup, the nature of the chemical bonding in the two compounds is subtly different; in the (Eu(1-x)Ca(x))(2)Ge(2)Pb structure, Ge and Pb are positioned at a relatively shorter distance from one another (<3.0 ?). The close proximity of the atoms leads to interactions, which are seen for the first time in an extended structure and can be suggested to have a covalent character. This conjecture is supported by extensive electronic band-structure calculations using first principles. Magnetic susceptibility measurements reveal Eu(2+) ground state ([Xe]4f(7) configuration) and the presence of an antiferromagnetic ordering at cryogenic temperatures. 相似文献
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A perturbed chain equation of state for the solid phase has been derived. Although the equation is general with respect to intermolecular potential, we incorporate the Lennard-Jones potential in this work in order to compare results from the model with available Monte Carlo simulation data. Two forms of the radial distribution function for the hard-sphere solid chain reference state are used in the model. First, a theoretically rigorous approach is taken by using a correlation of actual solid-phase Monte Carlo hard-sphere chain data for the radial distribution function. This results in good agreement with the Monte Carlo data only at high density. Second, a simple extended-density approximation was used for the radial distribution function. This second approach was found to work well across the entire density range including the vicinity of the solid-fluid equilibrium. 相似文献