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Kul Ismail Bhat Krishna Knox Alyssa Fischer-Drowos Shirley 《Journal of solution chemistry》2021,50(8):1113-1123
Journal of Solution Chemistry - Measurements of density and speed of sound are reported for phenylboronic acid–water solutions for molalities ranging from 0.0098 to... 相似文献
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Ashish N. Basuray Dr. Henri‐Pierre Jacquot de Rouville Dr. Karel J. Hartlieb Dr. Takashi Kikuchi Nathan L. Strutt Carson J. Bruns Michael W. Ambrogio Alyssa‐Jennifer Avestro Dr. Severin T. Schneebeli Albert C. Fahrenbach Prof. J. Fraser Stoddart 《Angewandte Chemie (International ed. in English)》2012,51(47):11872-11877
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Piyawan Krisanangkura Alyssa M. Packard Jacqueline Burgher Frank D. Blum 《Journal of Polymer Science.Polymer Physics》2010,48(17):1911-1918
The H‐bonding of carbonyl groups on a series of methacrylate polymers with silanols on fumed silica was studied with transmission FTIR. The set included poly(alkyl methacrylates) with alkyl groups, (n‐CnH2n+1) of n = 1, 2, 4, and 12 and poly(benzyl methacrylate). Shifts in the vibrational frequencies for bound carbonyl groups (of ~20 cm?1 lower than those found in the bulk) were observed in the adsorbed polymer samples. A series of samples with different adsorbed amounts (varying from 0.5 to 2.0 mg m?2) of each polymer was prepared to determine the effect of the side chain on the H‐bonding. The fractions of bound carbonyls, p, for each of the methacrylate polymers studied, were calculated from a model based on the ratios of the absorption coefficients of the bound to free carbonyl resonances, X (= αb/αf). The X values were determined from linear regressions of the ratios of the free to bound carbonyl intensities as a function of the amounts of adsorbed polymer, Mt. The bound fractions, p, were observed to decrease with increase in adsorbed amounts and with increase in the lengths of the side chains of the methacrylate polymers, except for poly(lauryl methacrylate) (PLMA). PLMA has a very low glass transition temperature (Tg) and is likely rubbery on the surface, whereas the other polymers are likely glassy at ambient temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1911–1918, 2010 相似文献
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Szajnman SH Rosso VS Malayil L Smith A Moreno SN Docampo R Rodriguez JB 《Organic & biomolecular chemistry》2012,10(7):1424-1433
α-Fluorinated-1,1-bisphosphonic acids derived from fatty acids were designed, synthesized and biologically evaluated against Trypanosoma cruzi, the etiologic agent of Chagas disease, and against Toxoplasma gondii, the agent responsible for toxoplasmosis, and also towards the target parasitic enzymes farnesyl pyrophosphate synthase of T. cruzi (TcFPPS) and T. gondii (TgFPPS). Interestingly, 1-fluorononylidene-1,1-bisphosphonic acid (compound 43) proved to be an extremely potent inhibitor of the enzymatic activity of TgFPPS at the low nanomolar range, exhibiting an IC(50) of 30 nM. This compound was two-fold more potent than risedronate (IC(50) = 74 nM) that was taken as a positive control. This enzymatic activity was associated with a strong cell growth inhibition against tachyzoites of T. gondii, with an IC(50) value of 2.7 μM. 相似文献
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Nicholas S. Labrum Alyssa C. Cabelof Prof. Dr. Kenneth G. Caulton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(61):13915-13926
Reduction of the bis-pyrazolyl pyridine complex [CrL]2 with 4 KC8, followed by addition of one azobenzene (overall mole ratio 1:4:1), PhNNPh, transfers reducing equivalents to three azobenzenes, to form [K3Cr(PhNNPh)3]. This has three κ2 PhNNPh2− ligands and K+ bound to nitrogen atoms of azobenzene. When the stoichiometry is modified to 1:4:3, the product is changed to [K2CrL(PhNNPh)2], which has C2 symmetry except for the intimate ion pairing of two K+ ions to reduced azobenzene nitrogen atoms, and to pyrazolate and phenyl rings. The origin of the observed delivery of reducing equivalents to several, not to a single N=N bond, is traced to the resistance of the one-electron-reduced substrate to receiving a second electron, and is thus a general phenomenon. [CrL]2 alone is shown to be a two-electron reductant towards benzo[c]cinnoline (BCC) resulting in a product of formula [Cr2L2(BCC)], in which the reducing equivalents originate purely from CrII. An analogous study of the reaction of [CrL]2 with azobenzene yields [Cr2L2(PhNNPh)(THF)], an adduct in which one THF has displaced one of four hydrazide nitrogen/Cr bonds. Together these illustrate different modes for the Cr2L2 unit to bind and reduce the N=N bond. Collectively, these results show that two divalent Cr, without added K0, have the ability to reduce the N=N bond. Further KC8 reduction of preformed Cr2L2(RNNR) inevitably gives products in which K+ stabilizes the charge in the increasingly electron-rich nitrogen atoms, in a phenomenon which mimics proton coupled electron transfer: K+ performs the role of H+. A least-squares fit of the two singly reduced DFT structures shows that the only major change is a re-orientation of one of the two phenyl rings in order to avoid repulsion with potassium but to still allow interaction of that phenyl π system with K+. This shows both the impact of K+, being modest to nitrogen/chromium interactions, but nevertheless accommodating some π donation of phenyl to potassium. Finally, delivering increasing equivalents of KC8 leads to complete cleavage of the N=N bond, and both N bind to three CrII. The varied impacts of the K+ electrophile on NN multiple bond reduction is discussed. 相似文献
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Dr. Alyssa M. Love Melissa C. Cendejas Michael P. Hanrahan Scott L. Carnahan Pajean Uchupalanun Prof. Dr. Aaron J. Rossini Prof. Dr. Ive Hermans 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(5):1052-1063
The complexity of variables during incipient wetness impregnation synthesis of supported metal oxides precludes an in-depth understanding of the chemical reactions governing the formation of the dispersed oxide sites. This contribution describes the use of vapor phase deposition chemistry (also known as grafting) as a tool to systematically investigate the influence of isopropanol solvent on VO(OiPr)3 anchoring during synthesis of vanadium oxide on silica. The availability of anchoring sites on silica was found to depend not only on the pretreatment of the silica but also on the solvent present. H-bond donors can reduce the reactivity of isolated silanols whereas disruption of silanol nests by H-bond acceptors can turn unreactive H-bonded silanols into reactive anchoring sites. The model suggested here can inform improved syntheses with increased dispersion of metal oxides on silica. 相似文献
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Daniel M. Beagan Alyssa C. Cabelof Maren Pink Veronica Carta Xinfeng Gao Kenneth G. Caulton 《Chemical science》2021,12(31):10664
The syntheses of (DIM)Ni(NO3)2 and (DIM)Ni(NO2)2, where DIM is a 1,4-diazadiene bidentate donor, are reported to enable testing of bis boryl reduced N-heterocycles for their ability to carry out stepwise deoxygenation of coordinated nitrate and nitrite, forming O(Bpin)2. Single deoxygenation of (DIM)Ni(NO2)2 yields the tetrahedral complex (DIM)Ni(NO)(ONO), with a linear nitrosyl and κ1-ONO. Further deoxygenation of (DIM)Ni(NO)(ONO) results in the formation of dimeric [(DIM)Ni(NO)]2, where the dimer is linked through a Ni–Ni bond. The lost reduced nitrogen byproduct is shown to be N2O, indicating N–N bond formation in the course of the reaction. Isotopic labelling studies establish that the N–N bond of N2O is formed in a bimetallic Ni2 intermediate and that the two nitrogen atoms of (DIM)Ni(NO)(ONO) become symmetry equivalent prior to N–N bond formation. The [(DIM)Ni(NO)]2 dimer is susceptible to oxidation by AgX (X = NO3−, NO2−, and OTf−) as well as nitric oxide, the latter of which undergoes nitric oxide disproportionation to yield N2O and (DIM)Ni(NO)(ONO). We show that the first step in the deoxygenation of (DIM)Ni(NO)(ONO) to liberate N2O is outer sphere electron transfer, providing insight into the organic reductants employed for deoxygenation. Lastly, we show that at elevated temperatures, deoxygenation is accompanied by loss of DIM to form either pyrazine or bipyridine bridged polymers, with retention of a BpinO− bridging ligand.Deoxygenation of nitrogen oxyanions coordinated to nickel using reduced borylated heterocycles leads to N–N bond formation and N2O liberation. The nickel dimer product facilitates NO disproportionation, leading to a synthetic cycle. 相似文献