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101.
Four metal‐ion‐binding nucleosides, viz. 2,6‐bis(1‐methylhydrazinyl)‐9‐(β‐D ‐ribofuranosyl)‐9H‐purine ( 2a ) and its N‐acetylated derivative, 2b , 2,4‐bis(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)‐5‐(β‐D ‐ribofuranosyl)pyrimidine ( 3 ), and 2,4‐bis(1‐methylhydrazinyl)‐5‐(β‐D ‐ribofuranosyl)pyrimidine ( 4 ) have been synthesized. The ability of these nucleosides and the previously prepared 2,6‐bis(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)‐9‐(β‐D ‐ribofuranosyl)‐9H‐purine to form Pd2+‐ and Hg2+‐mediated complexes with uridine has been studied by 1H‐NMR spectroscopy. To obtain additional support for the interpretation of the NMR data, comparative measurements on the ternary‐complex formation between pyridine‐2,6‐dicarboxamide ( 5 ), pyrimidine nucleosides, and K2PdCl4 were carried out. 相似文献
102.
103.
Chambreau SD Boatz JA Vaghjiani GL Koh C Kostko O Golan A Leone SR 《The journal of physical chemistry. A》2012,116(24):5867-5876
In order to better understand the volatilization process for ionic liquids, the vapor evolved from heating the ionic liquid 1-ethyl-3-methylimidazolium bromide (EMIM(+)Br(-)) was analyzed via tunable vacuum ultraviolet photoionization time-of-flight mass spectrometry (VUV-PI-TOFMS) and thermogravimetric analysis mass spectrometry (TGA-MS). For this ionic liquid, the experimental results indicate that vaporization takes place via the evolution of alkyl bromides and alkylimidazoles, presumably through alkyl abstraction via an S(N)2 type mechanism, and that vaporization of intact ion pairs or the formation of carbenes is negligible. Activation enthalpies for the formation of the methyl and ethyl bromides were evaluated experimentally, ΔH(?)(CH(3)Br) = 116.1 ± 6.6 kJ/mol and ΔH(?)(CH(3)CH(2)Br) = 122.9 ± 7.2 kJ/mol, and the results are found to be in agreement with calculated values for the S(N)2 reactions. Comparisons of product photoionization efficiency (PIE) curves with literature data are in good agreement, and ab initio thermodynamics calculations are presented as further evidence for the proposed thermal decomposition mechanism. Estimates for the enthalpy of vaporization of EMIM(+)Br(-) and, by comparison, 1-butyl-3-methylimidazolium bromide (BMIM(+)Br(-)) from molecular dynamics calculations and their gas phase enthalpies of formation obtained by G4 calculations yield estimates for the ionic liquids' enthalpies of formation in the liquid phase: ΔH(vap)(298 K) (EMIM(+)Br(-)) = 168 ± 20 kJ/mol, ΔH(f,?gas)(298 K) (EMIM(+)Br(-)) = 38.4 ± 10 kJ/mol, ΔH(f,?liq)(298 K) (EMIM(+)Br(-)) = -130 ± 22 kJ/mol, ΔH(f,?gas)(298 K) (BMIM(+)Br(-)) = -5.6 ± 10 kJ/mol, and ΔH(f,?liq)(298 K) (BMIM(+)Br(-)) = -180 ± 20 kJ/mol. 相似文献
104.
Golub IE Filippov OA Gutsul EI Belkova NV Epstein LM Rossin A Peruzzini M Shubina ES 《Inorganic chemistry》2012,51(12):6486-6497
The mechanism of transition-metal tetrahydroborate dimerization was established for the first time on the example of (Ph(3)P)(2)Cu(η(2)-BH(4)) interaction with different proton donors [MeOH, CH(2)FCH(2)OH, CF(3)CH(2)OH, (CF(3))(2)CHOH, (CF(3))(3)CHOH, p-NO(2)C(6)H(4)OH, p-NO(2)C(6)H(4)N═NC(6)H(4)OH, p-NO(2)C(6)H(4)NH(2)] using the combination of experimental (IR, 190-300 K) and quantum-chemical (DFT/M06) methods. The formation of dihydrogen-bonded complexes as the first reaction step was established experimentally. Their structural, electronic, energetic, and spectroscopic features were thoroughly analyzed by means of quantum-chemical calculations. Bifurcate complexes involving both bridging and terminal hydride hydrogen atoms become thermodynamically preferred for strong proton donors. Their formation was found to be a prerequisite for the subsequent proton transfer and dimerization to occur. Reaction kinetics was studied at variable temperature, showing that proton transfer is the rate-determining step. This result is in agreement with the computed potential energy profile of (Ph(3)P)(2)Cu(η(2)-BH(4)) dimerization, yielding [{(Ph(3)P)(2)Cu}(2)(μ,η(4)-BH(4))](+). 相似文献
105.
Strong Direct Magnetic Coupling in a Dinuclear CoII Tetrazine Radical Single‐Molecule Magnet 下载免费PDF全文
Toby J. Woods Dr. Maria Fernanda Ballesteros‐Rivas Sergei M. Ostrovsky Andrew V. Palii Oleg S. Reu Sophia I. Klokishner Dr. Kim R. Dunbar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(29):10302-10305
The ligand‐centered radical complex [(CoTPMA)2‐μ‐bmtz.?](O3SCF3)3 ? CH3CN (bmtz=3,6‐bis(2′‐pyrimidyl)‐1,2,4,5‐tetrazine, TPMA=tris‐(2‐pyridylmethyl)amine) has been synthesized from the neutral bmtz precursor. Single‐crystal X‐ray diffraction studies have confirmed the presence of the ligand‐centered radical. The CoII complex exhibits slow paramagnetic relaxation in an applied DC field with a barrier to spin reversal of 39 K. This behavior is a result of strong antiferromagnetic metal–radical coupling combined with positive axial and strong rhombic anisotropic contributions from the CoII ions. 相似文献
106.
Rustam T. Iminov Anton V. Tverdokhlebov Andrey A. Tolmachev Yulian M. Volovenko Svetlana V. Shishkina Oleg. V. Shishkin 《Tetrahedron》2012,68(14):3098-3102
Heating of N-{2-[(R-amino)carbonyl]phenyl}prolinamides in triethyl orthoformate solution was found to give 6-R-5,6,6a,8,9,10,10a,11-octahydropyrrolo[1′,2′:3,4]imidazo[1,2-a]quinazoline-5,11-diones. Similar reaction of N-{2-[(R-amino)carbonyl]phenyl}thiazolidine-4-carboxamides afforded 6-R-5,6,6a,10,10a,11-hexahydrothiazolo[3′,4′:3,4]imidazo[1,2-a]quinazoline-5,11-diones. The relative configuration of C-6a and C-10a centres of the tetracyclic compounds obtained was assigned as trans on the basis of X-ray crystallographic study. 相似文献
107.
Nikolai A. Ustynyuk Oleg V. Gusev Lyudmila N. Novikova Mikhail G. Peterleitner Larisa I. Denisovich Tat’yana A. Peganova Oleg V. Semeikin Dmitry A. Valyaev 《Journal of Solid State Electrochemistry》2007,11(12):1621-1634
In this review, redox-induced reactions of π- and σ,π-complexes leading to the selective formation (or cleavage) of C–H, C–C,
and C–O bonds have been summarized. To illustrate the synthetic potential of such methodology, the following representative
reactions studied in our group are discussed: (1) oxidatively induced hydrogen elimination from “open” cyclic diene and dienyl
complexes resulting in formation of “closed” dienyl and arene complexes, respectively; (2) reductive activation of C–H bonds
in diene, vinylidene, and carbyne complexes forming new multiple C–C bonds; (3) oxidative dehydrodimerization of vinylidene
complexes into binuclear μ-divinylidene species; and (4) oxidatively induced addition of oxygen nucleophiles to μ-divinylidene
complexes affording cyclic μ-dicarbene derivatives.
Oleg V. Gusev, deceased on October 31. 相似文献
108.
Roman V. Tominov Zakhar E. Vakulov Vadim I. Avilov Daniil A. Khakhulin Nikita V. Polupanov Vladimir A. Smirnov Oleg A. Ageev 《Molecules (Basel, Switzerland)》2021,26(1)
We have experimentally studied the influence of pulsed laser deposition parameters on the morphological and electrophysical parameters of vanadium oxide films. It is shown that an increase in the number of laser pulses from 10,000 to 60,000 and an oxygen pressure from 3 × 10−4 Torr to 3 × 10−2 Torr makes it possible to form vanadium oxide films with a thickness from 22.3 ± 4.4 nm to 131.7 ± 14.4 nm, a surface roughness from 7.8 ± 1.1 nm to 37.1 ± 11.2 nm, electron concentration from (0.32 ± 0.07) × 1017 cm−3 to (42.64 ± 4.46) × 1017 cm−3, electron mobility from 0.25 ± 0.03 cm2/(V·s) to 7.12 ± 1.32 cm2/(V·s), and resistivity from 6.32 ± 2.21 Ω·cm to 723.74 ± 89.21 Ω·cm. The regimes at which vanadium oxide films with a thickness of 22.3 ± 4.4 nm, a roughness of 7.8 ± 1.1 nm, and a resistivity of 6.32 ± 2.21 Ω·cm are obtained for their potential use in the fabrication of ReRAM neuromorphic systems. It is shown that a 22.3 ± 4.4 nm thick vanadium oxide film has the bipolar effect of resistive switching. The resistance in the high state was (89.42 ± 32.37) × 106 Ω, the resistance in the low state was equal to (6.34 ± 2.34) × 103 Ω, and the ratio RHRS/RLRS was about 14,104. The results can be used in the manufacture of a new generation of micro- and nanoelectronics elements to create ReRAM of neuromorphic systems based on vanadium oxide thin films. 相似文献
109.
Ekaterina V. Pokochueva Dr. Dudari B. Burueva Dr. Oleg G. Salnikov Prof. Igor V. Koptyug 《Chemphyschem》2021,22(14):1421-1440
Parahydrogen-induced polarization with heterogeneous catalysts (HET-PHIP) has been a subject of extensive research in the last decade since its first observation in 2007. While NMR signal enhancements obtained with such catalysts are currently below those achieved with transition metal complexes in homogeneous hydrogenations in solution, this relatively new field demonstrates major prospects for a broad range of advanced fundamental and practical applications, from providing catalyst-free hyperpolarized fluids for biomedical magnetic resonance imaging (MRI) to exploring mechanisms of industrially important heterogeneous catalytic processes. This review covers the evolution of the heterogeneous catalysts used for PHIP observation, from metal complexes immobilized on solid supports to bulk metals and single-atom catalysts and discusses the general visions for maximizing the obtained NMR signal enhancements using HET-PHIP. Various practical applications of HET-PHIP, both for catalytic studies and for potential production of hyperpolarized contrast agents for MRI, are described. 相似文献
110.
At pH = 1 and 25 degrees C, the Fenton-like reactions of Fe(aq)(2+) with hydroperoxorhodium complexes LRh(III)OOH(2+) (L = (H(2)O)(NH(3))(4), k = 30 M(-1) s(-1), and L = L(2) = (H(2)O)(meso-Me(6)-[14]aneN(4)), k = 31 M(-1) s(-1)) generate short-lived, reactive intermediates, believed to be the rhodium(IV) species LRh(IV)O(2+). In the rapid follow-up steps, these transients oxidize Fe(aq)(2+), and the overall reaction has the standard 2:1 [Fe(aq)(2+)]/[LRhOOH(2+)] stoichiometry. Added substrates, such as alcohols, aldehydes, and (NH(3))(4)(H(2)O)RhH(2+), compete with Fe(aq)(2+) for LRh(IV)O(2+), causing the stoichiometry to change to <2:1. Such competition data were used to determine relative reactivities of (NH(3))(4)RhO(2+) toward CH(3)OH (1), CD(3)OH (0.2), C(2)H(5)OH (2.7), 2-C(3)H(7)OH (3.4), 2-C(3)D(7)OH (1.0), CH(2)O (12.5), C(2)H(5)CHO (45), and (NH(3))(4)RhH(2+) (125). The kinetics and products suggest hydrogen atom abstraction for (NH(3))(4)RhO(2+)/alcohol reactions. A short chain reaction observed with C(2)H(5)CHO is consistent with both hydrogen atom and hydride transfer. The rate constant for the reaction between Tl(aq)(III) and L(2)Rh(2+) is 2.25 x 10(5) M(-1) s(-1). 相似文献