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71.
Reactivity of [Ge9{Si(SiMe3)3}3]− Towards Transition‐Metal M2+ Cations: Coordination and Redox Chemistry 下载免费PDF全文
Dr. Oleksandr Kysliak Dr. Claudio Schrenk Prof. Dr. Andreas Schnepf 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(52):18787-18793
Recently the metalloid cluster compound [Ge9Hyp3]? ( 1 ; Hyp=Si(SiMe3)3) was oxidatively coupled by an iron(II) salt to give the largest metalloid Group 14 cluster [Ge18Hyp6]. Such redox chemistry is also possible with different transition metal (TM) salts TM2+ (TM=Fe, Co, Ni) to give the TM+ complexes [Fe(dppe)2][Ge9Hyp3] ( 3 ; dppe=1,2‐bis(diphenylphosphino)ethane), [Co(dppe)2][Ge9Hyp3] ( 4 ), [Ni(dppe)(Ge9Hyp3)] ( 5 ) and [Ni(dppe)2(Ge9Hyp3)]+ ( 6 ). Such a redox reaction does not proceed for Mn, for which a salt metathesis gives the first open shell [Hyp3Ge9‐M‐Ge9Hyp3] cluster ( 2 ; M=Mn). The bonding of the transition metal atom to 1 is also possible for Ni (e.g., compound 6 ), in which one or even two nickel atoms can bind to 1 . In contrast to this in case of the Fe and Co compounds 3 and 4 , respectively, the transition‐metal atom is not bound to the Ge9 core of 1 . The synthesis and the experimentally determined structures of 2 – 6 are presented. Additionally the bonding within 2 – 6 is analyzed and discussed with the aid of EPR measurements and quantum chemical calculations. 相似文献
72.
Dyachenko Alla Ischenko Olena Diyuk Vitaliy Goncharuk Olena Borysenko Mykola Mischanchuk Oleksandr Zakharova Tetiana Pryhunova Olha Sternik Dariush Lisnyak Vladyslav 《Research on Chemical Intermediates》2022,48(6):2607-2625
Research on Chemical Intermediates - Oxide Ni(80)Fe(20)/SiO2, Co(93)Fe(7)/SiO2, and Ni(19)Co(77)Fe(4)/SiO2 nanocomposites (NCs) were prepared using highly dispersed silica. It was modified by... 相似文献
73.
Oleksandr Trotsenko Yuri Roiter Sergiy Minko 《Journal of polymer science. Part A, Polymer chemistry》2010,48(14):1623-1627
In this article, we compare structures of protonated poly(2-vinylpyridine) globules (2D compact coils on the surface) adsorbed on the mica surface from aqueous solution when the shrinking is brought about either by discharging the molecules at an elevated pH or by adding monovalent and polyvalent salts. We study the structure of the PE coils using in situ atomic force microscopy experiments in aqueous solutions in a liquid cell. The abrupt coil-to-globule transition caused by pH changes and the discharge of polymer chains resulted in compact globules. If the pH corresponding to extended coil conformation remains unchanged, the coil shrinks due to the added salt. The size of the globule in the latter case corresponds to the unperturbed dimension of the polymer coil. There is no essential difference in the dimensions of the globules as obtained in the presence of monovalent and multivalent counterions for the studied ionic strength. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1623–1627, 2010 相似文献
74.
75.
Nath KG Ivasenko O Miwa JA Dang H Wuest JD Nanci A Perepichka DF Rosei F 《Journal of the American Chemical Society》2006,128(13):4212-4213
We demonstrate a surprising cooperative adsorption process at the liquid-solid interface, involving self-assembly in which a three-fold hydrogen-bonding unit (trimesic acid, TMA) is forced into a linear pattern by noncovalent interaction with an alcohol. Our work shows that the unexpected linear pattern formed by coadsorption of TMA and alcohols can be modulated in size by choosing alcohols with different chain lengths. 相似文献
76.
We establish Lamperti representations for semi-stable Markov processes in locally compact groups. We also study the particular cases of processes with values in R and C under the hypothesis that they do not visit 0. These Lamperti representations yield some properties of these semi-stable Markov processes. 相似文献
77.
Chatterjee S Pathmasiri W Plashkevych O Honcharenko D Varghese OP Maiti M Chattopadhyaya J 《Organic & biomolecular chemistry》2006,4(9):1675-1686
We here show that the pKa (error limit: 0.01 to 0.03 pKa unit) of a nucleobase in a nucleotide can be modulated by the chemical nature of the 2'-substituent at the sugar moiety. This has been evidenced by the measurement of nucleobase pKa in 47 different model nucleoside 3',5'-bis- and 3'-mono-ethylphosphates. The fact that the electronic character of each of the 2'-substituents (Fig. 1) alters the chemical shift of the H2' sugar proton, and also alters the pKa of the nucleobase in the nucleotides has been evidenced by a correlation plot of pKa of N3 of pyrimidine (T/C/U) or pKa of N7 of 9-guaninyl with the corresponding deltaH2' chemical shifts at the neutral pH, which shows linear correlation with high Pearson's correlation coefficients (R = 0.85-0.97). That this modulation of the pKa of the nucleobase by a 2'-substituent is a through-bond as well as through-space effect has been proven by ab initio determined pKa estimation. Interestingly, experimental pKas of nucleobases from NMR titration and the calculated pKas (by ab initio calculations utilizing closed shell HF 6-31G** basis set) are linearly correlated with R = 0.98. It has also been observed that the difference of ground and protonated/de-protonated HOMO orbital energies (DeltaHOMO, a.u.) for the nucleobases (A/G/C/T/U) are well correlated with their pK(a)s in different 2'-substituted 3',5'-bis-ethylphosphate analogs suggesting that only the orbital energy of HOMO can be successfully used to predict the modulation of the chemical reactivity of the nucleobase by the 2'-substituent. It has also been demonstrated that pKa values of nucleobases in 3',5'-bis-ethylphosphates (Table 1) are well correlated with the change in dipole moment for the respective nucleobases after protonation or de-protonation. This work thus unambiguously shows that alteration of the thermodynamic stability (Tm) of the donor-acceptor complexes [ref. 20], as found with various 2'-modified duplexes in the antisense, siRNA or in triplexes by many workers in the field, is a result of alteration of the pseudoaromatic character of the nucleobases engineered by alteration of the chemical nature of the 2'-substitution. 相似文献
78.
Andreas Müller‐Schiffmann Julia Mrz‐Berberich Aksana Andreyeva Raik Rnicke Dirk Bartnik Oleksandr Brener Janine Kutzsche Anselm H. C. Horn Marco Hellmert Jolanta Polkowska Kurt Gottmann Klaus G. Reymann S. Aileen Funke Luitgart Nagel‐Steger Christine Moriscot Guy Schoehn Heinrich Sticht Dieter Willbold Thomas Schrader Carsten Korth 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2010,122(46):8925-8928
79.
Natalia A. Kopylova Oleksandr O. Grygorenko Igor V. Komarov Ulrich Groth 《Tetrahedron: Asymmetry》2010,21(23):2868-2871
A novel approach to the synthesis of an enantiopure bicyclic proline analogue, hexahydrocyclopenta[b]pyrrole-6a(1H)-carboxylic acid (‘2,3-propanoproline’), has been developed. The method relied on tandem Strecker-nucleophilic cyclization reaction of 2-(2-bromoethyl)cyclopentanone. The overall synthetic scheme included six steps and resulted in 18% overall yield of both enantiomers of the title amino acid. 相似文献
80.
Vladimir L. Solozhenko Yann Le Godec Oleksandr O. Kurakevych 《Comptes Rendus Chimie》2006,9(11-12):1472
Solid-state synthesis of boron subnitride, B6N, as a result of chemical interaction between boron and boron nitride at 7.5 GPa and 1700 °C has been previously reported by Hubert et al. However, a critical analysis of the results has shown that the evidence for the formation of boron subnitride with B6O-like structure is inconclusive. We have studied in situ the interaction between boron and BN at the same p–T conditions using X-ray diffraction with synchrotron radiation. At 7.4 GPa and 1700 °C the formation of a new phase has not been observed. At the same time, HP–HT treatment has resulted in strong and unpredictable preferred orientation of boron crystallites. This leads to the rise of some weak boron reflections that might be erroneously attributed to the appearance of a new phase. To cite this article: V.L. Solozhenko et al., C. R. Chimie 9 (2006). 相似文献