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21.
Grirrane A Pastor A Galindo A Alvarez E Mealli C Ienco A Orlandini A Rosa P Caneschi A Barra AL Sanz JF 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(38):10600-10617
Compounds based on the Mn-tda unit (tda=S(CH(2)COO)(2)(-2) ) and N co-ligands have been analyzed in terms of structural, spectroscopic, magnetic properties and DFT calculations. The precursors [Mn(tda)(H(2)O)](n) (1) and [Mn(tda)(H(2)O)(3)]·H(2)O (2) have been characterized by powder and X-ray diffraction, respectively. Their derivatives with bipyridyl-type ligands have formulas [Mn(tda)(bipy)](n) (3), [{Mn(N-N)}(2)(μ-H(2)O)(μ-tda)(2)](n) (N-N=4,4'-Me(2)bipy (4), 5,5'-Me(2)bipy, (5)) and [Mn(tda){(MeO)(2)bipy}·2H(2)O](n) (6). Depending on the presence/position of substituents at bipy, the supramolecular arrangement can affect the metal coordination type. While all the complexes consist of 1D coordination polymers, only 3 has a copper-acetate core with local trigonal prismatic metal coordination. The presence of substituents in 4-6, together with water co-ligands, reduces the supramolecular interactions and typical octahedral Mn(II) ions are observed. The unicity of 3 is also supported by magnetic studies and by DFT calculations, which confirm that the unusual Mn coordination is a consequence of extended noncovalent interactions (π-π stacking) between bipy ligands. Moreover, 3 is an example of broken paradigm for supramolecular chemistry. In fact, the desired stereochemical properties are achieved by using rigid metal building blocks, whereas in 3 the accumulation of weak noncovalent interactions controls the metal geometry. Other N co-ligands have also been reacted with 1 to give the compounds [Mn(tda)(phen)](2)·6H(2)O (7) (phen=1,10-phenanthroline), [Mn(tda)(terpy)](n) (8) (terpy=2,2':6,2'-terpyridine), [Mn(tda)(pyterpy)](n) (9) (pyterpy=4'-(4-pyridyl)-2,2':6,2'-terpyridine), [Mn(tda)(tpt)(H(2)O)]·2H(2)O (10) and [Mn(tda)(tpt)(H(2)O)](2)·2H(2)O (11) (tpt=2,4,6-tris(2-pyridyl)-1,3,5-triazine). Their identified mono-, bi- or polynuclear structures clearly indicate that hydrogen bonding is variously competitive with π-π stacking. 相似文献
22.
Didier?BegueEmail author Claude?Pouchan Jean-Claude?Guillemin Abdessamad?Benidar 《Theoretical chemistry accounts》2012,131(3):1122
Based on accurate computational results, the IR spectra of diborane B2H6 and its deuterated derivative B2D6 were experimentally revisited to reconsider or complete their band assignments. A pure, variational approach, developed in
both mechanical and electrical anharmonicities, was applied to study the diborane molecule for which many uncertainties remain
in the spectral IR assignment. This work, together with all the experiments on this system over recent decades, shows the
difficulty of interpreting the spectral data, making it a “benchmark” ideal for testing the mathematical approaches for the
implementation of vibrational codes. 相似文献
23.
Mohamed Bencheikh Abdelmajid Maghnouj Jaouad Tajmouati Abdessamad Didi Ahad Olah Ezzati 《Physics of Particles and Nuclei Letters》2017,14(5):780-787
The Monte Carlo model for the photon-beam output from the Varian Clinac 2100 linear accelerator was validated to compare the calculated to measured PDD and beam dose profiles The Monte Carlo calculation method is considered to be the most accurate method for dose calculation in radiotherapy. The objective of this study is to build a Monte Carlo geometry of Varian Clinac 2100 linear accelerator as realistically as possible. The Monte Carlo codes used in this work were the BEAMnrc code to simulate the photons beam and the DOSXYZnrc code to examinate the absorbed dose in the water phantom. We have calculated percentage depth dose (PDD) and beam profiles of the 6 MV photon beam for the 6 × 6 cm2, 10 × 10 cm2 and 15 × 15 cm2 field sizes. We have used the gamma index technique for the quantitative evaluation to compare the measured and calculated distributions. Good agreement was found between calculated PDD and beam profile compared to measured data. The comparison was evaluated using the gamma index method and the criterions were 3% for dose difference and 3 mm for distance to agreement. The gamma index acceptance rate was more than 97% of both distribution comparisons PDDs and dose profiles and our results were more developed and accurate. The Varian Clinac 2100 linear accelerator was accurately modeled using Monte Carlo codes: BEAMnrc and DOSXYZnrc codes package. 相似文献
24.
Dr. Yaroslav Grosu Dr. Mian Li Yun‐Lei Peng Dong Luo Prof. Dan Li Dr. Abdessamad Faik Prof. Jean‐Marie Nedelec Prof. Jean‐Pierre Grolier 《Chemphyschem》2016,17(21):3359-3364
A molecular spring formed by a hydrophobic metal–organic framework Cu2(tebpz) (tebpz=3,3′,5,5′‐tetraethyl‐4,4′‐bipyrazolate) and water is presented. This nanoporous heterogeneous lyophobic system (HLS) has exceptional properties compared to numerous reported systems of such type in terms of stability, efficiency, and operating pressure. Mechanical and thermal energetic characteristics as well as stability of the system are discussed and compared in detail with those of other previously reported HLS. 相似文献
25.
26.
Khalid Hattaf Noura YousfiAbdessamad Tridane 《Nonlinear Analysis: Real World Applications》2012,13(4):1866-1872
The rate of infection in many virus dynamics models is assumed to be bilinear in the virus and uninfected target cells. In this paper, the dynamical behavior of a virus dynamics model with general incidence rate and cure rate is studied. Global dynamics of the model is established. We prove that the virus is cleared and the disease dies out if the basic reproduction number R0≤1 while the virus persists in the host and the infection becomes endemic if R0>1. 相似文献
27.
To prepare two new glucuronide conjugates, allyl ester and allyl carbonates were used as protecting groups of the glucuronic moiety. In this way, an aniline glycosyl carbamate spacer linked to the 2'-OH of paclitaxel was obtained. By using palladium chemistry, an efficient one-step removal of all the allyl groups at the end of the synthesis afforded the desired compounds in good yields. 相似文献
28.
Lena Hammerschmidt Abdessamad Debbab Tu Duong Ngoc Victor Wray Catalina Perèz Hemphil WenHan Lin Heike Broetz-Oesterhelt Matthias U. Kassack Peter Proksch Amal H. Aly 《Tetrahedron letters》2014
Five new polyketide derivatives, 6′-hydroxypestalotiopsone C (1), acropyrone (2), bicytosporone D (3), waol acid (4), and pestalotiopene C (5), together with seven known metabolites (6–12), were obtained from extracts of the endophytic fungus Acremonium strictum, isolated from the mangrove tree Rhizophora apiculata. The structures of the isolated compounds were elucidated on the basis of comprehensive NMR and MS analysis. Compounds 6, 7, and 9 showed moderate cytotoxic activity against human cisplatin-sensitive (IC50 values 27.1, 76.2, and 8.3 μM, respectively) and resistant A2780 cell lines (IC50 values 12.6, 30.1, and 19.0 μM, respectively), whereas only 9 exhibited antibacterial activity against Staphylococcus aureus (MIC value 14.3 μM). 相似文献
29.
Festus Basden Chiedu Okoye Abdessamad Debbab Victor Wray Charles Okechukwu Esimone Patience Ogoamaka Osadebe Peter Proksch 《Tetrahedron letters》2014
Maytenus senegalensis Lam. (Celastraceae) leaves are traditionally used in West Africa for the management of cancer and other disorders associated with inflammation. In this study, bioactivity-guided fractionation of the methanol leaf extract of Maytenus senegalensis led to the isolation of 11 compounds, including the new phenyldilactone, maysedilactone (1). All isolated compounds were tested for cytotoxicity against mouse lymphoma cell line (L5178Y). Only (−) epigallocathechin showed high cytotoxicity and completely inhibited cell growth at the investigated dose of 10 μg/mL. This result supports the claimed efficacy of Maytenus senegalensis leaf extract in ethnomedicinal treatment of cancer. 相似文献
30.
Antonius R.B. Ola Abdessamad Debbab Amal H. Aly Attila Mandi Ilka Zerfass Alexandra Hamacher Matthias U. Kassack Heike Brötz-Oesterhelt Tibor Kurtan Peter Proksch 《Tetrahedron letters》2014
Neosartorin (1) was isolated from the endophytic fungus Aspergillus fumigatiaffinis. The absolute configuration of 1, including both axial and central chirality elements, was established as (aR,5S,10R,5′S,6′S,10′R) for the first time on the basis of its electronic circular dichroism (ECD) spectra aided with TDDFT–ECD calculations. Neosartorin (1) exhibited substantial antibacterial activity against a broad spectrum of Gram-positive bacterial species including staphylococci, streptococci, enterococci, and Bacillus subtilis with minimal inhibitory concentrations in the range of 4–32 μg/mL. When the toxicity of 1 against eukaryotic cells was measured using a panel of different cancer cell lines such as HELA and BALB/3T3, the average IC50 values exceeded 32 μg/mL. 相似文献