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51.
This article presents the static dipole polarizabilities of 4d transition-metal monohalides in the framework of density functional theory. The behavior of a large number of density functionals, including various types of the local spin density approximation (LSDA), the generalized gradient approximation (GGA), meta GGA (MGGA), hybrid GGA (HGGA), and hybrid meta GGA (HMGGA), has been assessed in polarizability calculations. The highly accurate CCSD(T) methodology is used to benchmark a variety of functionals. Our results indicate that there is a large variation in performance of the various functionals of each type in the calculation of the dipole polarizability. It turned out that, in the LSDA class, SVWN5 gives better results than SVWN3 for the reference values. Of the GGA methods, BP86 and BPW91 give the best results for our data set, followed by G96LYP. The TPSS functional is the best method of the MGGA class, followed by the VSXC and BB95 functionals. Moreover, the B98 and mPW1PW91 functionals are the best methods of the HGGA lineage, predicting the most accurate static dipole polarizabilities. Finally, TPSS1KCIS and PBE1KCIS are the best methods of the HMGGA functionals for that purpose. In general, it was found that the HGGA and HMGGA functionals provide the best performance. 相似文献
52.
Torsional and rotational spectroscopic properties of pyruvic acid are determined using highly correlated ab initio methods and combining two different theoretical approaches: Second order perturbation theory and a variational procedure in three-dimensions. Four equilibrium geometries of pyruvic acid, Tc, Tt, Ct, and CC, outcome from a search with CCSD(T)-F12. All of them can be classified in the Cs point group. The variational calculations are performed considering the three internal rotation modes responsible for the non-rigidity as independent coordinates. More than 50 torsional energy levels (including torsional subcomponents) are localized in the 406–986 cm−1 region and represent excitations of the ν24 (skeletal torsion) and the ν23 (methyl torsion) modes. The third independent variable, the OH torsion, interacts strongly with ν23. The A1/E splitting of the ground vibrational state has been evaluated to be 0.024 cm−1 as it was expected given the high of the methyl torsional barrier (338 cm−1). A very good agreement with respect to previous experimental data concerning fundamental frequencies (νCAL − νEXP ~ 1 cm−1), and rotational parameters (B0CAL − B0EXP < 5 MHz), is obtained. 相似文献
53.
In this work, neat and supported H6P2W18O62 into nanocage of β‐zeolite were synthesized. However, H6P2W18O62 into nanocage of β‐zeolite was synthesized via template synthesis method. In addition, TiO2 was supported on H6P2W18O62/β zeolite by impregnation method. The obtained materials were characterized by XRD, FT‐IR, UV‐Vis, FESEM and EDS techniques. Also, W and Ti contents of the catalyst were determined by ICP and EDS technique. The results reveal that the photocatalyst performance depends on catalyst loading, pH effect, and methyl orange concentration. Photocatalytic degradation of methyl orange follows a pseudo‐first order kinetic. The chemical oxygen demand (COD) experimental proved mineralization of methyl orange. Another reason for degradation and mineralization of methyl orange is the absence of hydrazine at the end of reaction which is one of the photodecolorization products. The plausible mechanism for photodegradation of MO was proposed. 相似文献
54.
In an aim to prove the efficiency of polyphenols of Rosa canina fruits in promoting human health. A methanolic extract of R. canina fruits was prepared by successive maceration with solvents of increasing polarity. The polyphenol composition was analyzed by HPLC–DAD–ESI–MS. The biological activity of this extract on SH-SY5Y cells and HepG2 cells was then studied. The antioxidant activity was tested by various in vitro tests such as DPPH-radical-scavenging activity, FRAP assay, hydroxyl radical scavenging assay and total antioxidant capacity. The subacute toxicity of R. canina was tested on female rats by repeated intraperitoneal administration of various doses. The phenolic profiles showed 25 antioxidants distributed into three classes of phenolic compounds: glycosylated and agglomerated flavonoids/isoflavonoids, tannins and phenanthrenes. Qualitative phytochemical analyses showed that this extract lacks alkaloids. The methanolic extract of R. canina fruits has a total antioxidant capacity of 82.69 ± 1.18 μg EAA/mg of methanol extract and the IC50 of the methods used is in the following increasing order: FRAP assay (61.88 μg/ml), then hydroxyl radical scavenging assay (67.45 μg/ml) and then DPPH radical-scavenging activity (129.81 μg/ml). The extract of R. canina did not cause any phenotypic signs of toxicity or mortality during and after treatment. The LD50 was >5,000 mg/kg, hence, R. canina was considered nontoxic. An in vivo study proved the protective effect of R. canina against cardiac and hepato-renal toxicities. These results drew the importance of a healthy diet, where diets rich in R. canina fruits can be used as a rich natural source of antioxidants and anticarcinogenic phenolic compounds. 相似文献
55.
Tashrifi Zahra Mohammadi-Khanaposhtani Mohammad Hamedifar Haleh Larijani Bagher Ansari Samira Mahdavi Mohammad 《Molecular diversity》2020,24(4):1385-1431
Molecular Diversity - 2-Amino-3-cyano-4H-chromenes are structural core motifs that received increasing attention in the last years due to their interesting potential pharmacological properties. In... 相似文献
56.
Alipour Lalami Ali Hassanzadeh Afrouzi Hamid Moshfegh Abouzar 《Journal of Thermal Analysis and Calorimetry》2019,136(5):1959-1975
Journal of Thermal Analysis and Calorimetry - An incompressible preconditioned lattice Boltzmann method (IPLBM) is proposed to investigate the fluid flow and heat transfer characteristics of... 相似文献
57.
58.
Dr. Samira Escopy Prof. Alexei V. Demchenko 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(14):e202103747
Thioglycosides are among the most common glycosyl donors that find broad application in the synthesis of glycans and glycoconjugates. However, the requirement for toxic and/or large access of activators needed for common glycosylations with thioglycosides remains a notable drawback. Due to the increased awareness of the chemical waste impact on the environment, synthetic studies have been driven by the goal of finding non-toxic reagents. The main focus of this review is to highlight recent methods for thioglycoside activation that rely on transition metal catalysis. 相似文献
59.
60.
Samira Dadkhah-Tehrani Mehdi Shabani-Nooshabadi Mohsen Moradian 《Journal of the Iranian Chemical Society》2018,15(1):171-179
The electrochemical synthesis of some new 2-[(4-methyl-2-pyridyl)amino)-1,4-benzenediol derivatives was performed via the electrochemical oxidation of hydroquinones in the presence of 2-amino-4-methylpyridine in an aqueous solution. The results demonstrate that electrogenerated p-benzoquinone participated in the Michael-type addition reaction via an electrochemical–chemical (EC) reaction mechanism pathway and converted to the corresponding 2-[(4-methyl-2-pyridyl)amino)-1,4-benzenediol derivatives. These new compounds have been synthesized in high yields and purity without using any toxic reagents or catalyst at the surface of carbon electrode. 相似文献