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81.
Dr. M. Merced Montero‐Campillo Prof. Manuel Yáñez Dr. Al Mokhtar Lamsabhi Prof. Otilia Mó 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(18):5309-5316
The most stable complexes between squaric acid and its sulfur‐ and selenium‐containing analogues (C4X4H2; X=O, S, Se) with BeY2 (Y=H, F) were studied by means of the Gaussian 04 (G4) composite ab initio theory. Squaric acid derivatives are predicted to be very strong acids in the gas phase; their acidity increases with the size of the chalcogen, with C4Se4H2 being the strongest acid of the series and stronger than sulfuric acid. The relative stability of the C4X4H2 ? BeY2 (X=O, S, Se; Y=H, F) complexes changes with the nature of the chalcogen atom; but more importantly, the formation of the C4X4H2 ? BeF2 complexes results in a substantial acidity enhancement of the squaric moiety owing to the dramatic electron‐density redistribution undergone by the system when the beryllium bond is formed. The most significant consequence of this acidity enhancement is that when BeF2 is replaced by BeH2, a spontaneous exergonic loss of H2 is observed regardless of the nature of the chalcogen atom. This is another clear piece of evidence of the important role that closed‐shell interactions play in the modulation of physicochemical properties of the Lewis acid and/or the Lewis base. 相似文献
82.
Ahmed Alsaedi Bashir Ahmad Mokhtar Kirane Belgacem Rebiai 《Mathematical Methods in the Applied Sciences》2019,42(12):4378-4393
Local and blowing‐up solutions for the Cauchy problem for a system of space and time fractional evolution equations with time‐nonlocal nonlinearities of exponential growth are considered. The existence and uniqueness of the local mild solution is assured by the Banach fixed point principle. Then, we establish a blow‐up result by Pokhozhaev capacity method. Finally, under some suitable conditions, an estimate of the life span of blowing‐up solutions is established. 相似文献
83.
Achouak Bekkai Belgacem Rebiai Mokhtar Kirane 《Mathematical Methods in the Applied Sciences》2019,42(6):1819-1830
In this paper, we are concerned with local existence and blowup of a unique solution to a time‐space fractional evolution equation with a time nonlocal nonlinearity of exponential growth. At first, we prove the existence and uniqueness of the local solution by the Banach contraction mapping principle. Then, the blowup result of the solution in finite time is established by the test function method with a judicious choice of the test function. 相似文献
84.
Résumé SoitT un courant positif fermé sur un voisinage de 0 dansC
n. Nous montrons queT admet un c?ne tangent (limite de la famille de ses homothétiques), dès que les masses projectivesv
T(r) convergent assez vite versV
T(0) pour que (v
T(r)−v
T(0))/r soit localement sommable enr=0. Cette condition suffisante est optimale: nous construisons des courants de bidegré (1, 1) n'ayant pas de c?ne tangent,
tels que l'intégrale de (v
T(r)−v
T(0))/r soit aussi peu divergente qu'on le souhaite. LorsqueT est le courant d'intégration sur un ensemble analytique, on vérifie quev
T(r)−v
T(0)=0r
ε), ce qui redonne le théorème de Thie-King sur l'existence du c?ne tangent. 相似文献
85.
Lamsabhi AM Mó O Yáñez M Guillemin JC Haldys V Tortajada J Salpin JY 《Journal of mass spectrometry : JMS》2008,43(3):317-326
The gas-phase reactions between Ni(+) ((2)D(5/2)) and aminoacetonitrile, a molecule of prebiological interest as possible precursor of glycine, have been investigated by means of mass spectrometry techniques. The mass-analyzed ion kinetic energy (MIKE) spectrum reveals that the adduct ions [NC--CH(2)--NH(2), Ni(+)] spontaneously decompose by loosing HCN, H(2), and H(2)CNH, the loss of hydrogen cyanide being clearly dominant. The structures and bonding characteristics of the aminoacetonitrile-Ni(+) complexes as well as the different stationary points of the corresponding potential energy surface (PES) have been theoretically studied by density functional theory (DFT) calculations carried out at B3LYP/6-311G(d,p) level. A cyclic intermediate, in which Ni(+) is bisligated to the cyano and the amino group, plays an important role in the unimolecular reactivity of these ions, because it is the precursor for the observed losses of HCN and H(2)CNH. In all mechanisms associated with the loss of H(2), the metal acts as hydrogen carrier favoring the formation of the H(2) molecule. The estimated bond dissociation energy of aminoacetonitrile-Ni(+) complexes (291 kJ mol(-1)) is larger than those measured for other nitrogen bases such as pyridine or pyrimidine and only slightly smaller than that of adenine. 相似文献
86.
Lamsabhi AM 《The journal of physical chemistry. A》2008,112(8):1791-1797
The specific hydration of 2,7-dimethyl-1,2,4-triazepine oxo-thio derivatives by one water molecule has been investigated at the B3LYP/6-311++G(3df,2p)//B3LYP/6-311+G(d,p) level of theory. The existence of different hydrogen bond (HB) donor and acceptor centers in these molecules led to different kinds of hydrogen bonds (CH-O, OH-S, NH-O, OH-N, and OH-O) and different kinds of complexes. Among them, the most stable structures correspond to complexes where the heteroatom X or Y at positions 3 and 5 behaves as HB acceptor and the hydrogen atom associated with the nitrogen atom at position 4 as HB donor. In accordance with previous studies, it has been shown that the thiocarbonyl group forms stronger HBs than the carbonyl group because the sulfur atom is a better HB acceptor than the oxygen one. With the help of the AIM (atoms in molecules) theory and ELF (electron localization function) analysis, it has been shown that, in the case of 3O5O, 3S5O, and 3S5S, the most basic site is the heteroatom at position 3, while in 3O5S species the most basic center is the sulfur atom. 相似文献
87.
Medina A Claessens CG Rahman GM Lamsabhi AM Mó O Yáñez M Guldi DM Torres T 《Chemical communications (Cambridge, England)》2008,(15):1759-1761
We have designed, synthesized and probed a dodecafluoro-subphthalocyaninato boron(III) unit, which bears a triphenylamine moiety in its axial position, as a novel electron donor-acceptor system. 相似文献
88.
89.
On a nonlocal problem for the Laplace equation in the unit ball with fractional boundary conditions
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Mokhtar Kirane Berikbol T. Torebek 《Mathematical Methods in the Applied Sciences》2016,39(5):1121-1128
In this paper, we investigate the correct solvability for the Laplace equation with a nonlocal boundary condition in the unit ball. The considered boundary operator is of fractional order. This problem is a generalization of the well‐known Bitsadze–Samarskii problem. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
90.
Joly N Vaillant C Cohen AM Martin P El Essassi M Massoui M Banoub J 《Rapid communications in mass spectrometry : RCM》2007,21(6):1062-1074
Electrospray ionization quadrupole time-of-flight (ESI-QqToF) mass spectra of the zwitteronic salts naloxonazine dihydrochloride 1 and naloxone hydrochloride 2, a common series of morphine opiate receptor antagonists, were recorded using different declustering potentials. The singly charged ion [M+H-2HCl](+) at m/z 651.3170 and the doubly charged ion [M+2H-2HCl](2+) at m/z 326.1700 were noted for naloxonazine dihydrochloride 1; and the singly charged ion [M+H-HCl](+) at m/z 328.1541 was observed for naloxone hydrochloride 2. Low-energy collision-induced dissociation tandem mass spectrometry (CID-MS/MS) experiments established the fragmentation routes of these compounds. In addition to the characteristic diagnostic product ions obtained, we noticed the formation of a series of radical product ions for the zwitteronic compounds 1 and 2, and also the formation of a distonic ion product formed from the singly charged ion [M+H-HCl](+) of naloxone hydrochloride 2. Confirmation of the various established fragmentation routes was effected by conducting a series of ESI-CID-QqTof-MS/MS product ion scans, which were initiated by CID in the atmospheric pressure/vacuum interface using a higher declustering potential. Deuterium labeling was also performed on the zwitteronic salts 1 and 2, in which the hydrogen atoms of the OH and NH groups were exchanged with deuterium atoms. Low-energy CID-QqTof-MS/MS product ion scans of the singly charged and doubly charged deuteriated molecules confirmed the initial fragmentation patterns proposed for the protonated molecules. Precursor ion scan analyses were also performed with a conventional quadrupole-hexapole-quadrupole tandem mass spectrometer and allowed the confirmation of the genesis of some diagnostic ions. 相似文献