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Sulfur versus Iron Oxidation in an Iron−Thiolate Model Complex
McDonald, Aidan R.,Bukowski, Michael R.,Farquhar, Erik R.,Jackson, Timothy A.,Koehntop, Kevin D.,Seo, Mi Sook,De Hont, Raymond F.,Stubna, Audria,Halfen, Jason A.,Mü,nck, Eckard,Nam, Wonwoo,Que, American Chemical Society 2010 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.132 No.48
<P>In the absence of base, the reaction of [Fe<SUP>II</SUP>(TMCS)]PF<SUB>6</SUB> (<B>1</B>, TMCS = 1-(2-mercaptoethyl)-4,8,11-trimethyl-1,4,8,11-tetraazacyclotetradecane) with peracid in methanol at −20 °C did not yield the oxoiron(IV) complex (<B>2</B>, [Fe<SUP>IV</SUP>(O)(TMCS)]PF<SUB>6</SUB>), as previously observed in the presence of strong base (KO<SUP>t</SUP>Bu). Instead, the addition of 1 equiv of peracid resulted in 50% consumption of <B>1</B>. The addition of a second equivalent of peracid resulted in the complete consumption of <B>1</B> and the formation of a new species <B>3</B>, as monitored by UV−vis, ESI-MS, and Mössbauer spectroscopies. ESI-MS showed <B>3</B> to be formulated as [Fe<SUP>II</SUP>(TMCS) + 2O]<SUP>+</SUP>, while EXAFS analysis suggested that <B>3</B> was an O-bound iron(II)−sulfinate complex (Fe−O = 1.95 Å, Fe−S = 3.26 Å). The addition of a third equivalent of peracid resulted in the formation of yet another compound, <B>4</B>, which showed electronic absorption properties typical of an oxoiron(IV) species. Mössbauer spectroscopy confirmed <B>4</B> to be a novel iron(IV) compound, different from <B>2</B>, and EXAFS (Fe?O = 1.64 Å) and resonance Raman (ν<SUB>Fe?O</SUB> = 831 cm<SUP>−1</SUP>) showed that indeed an oxoiron(IV) unit had been generated in <B>4</B>. Furthermore, both infrared and Raman spectroscopy gave indications that <B>4</B> contains a metal-bound sulfinate moiety (ν<SUB>s</SUB>(SO<SUB>2</SUB>) ≈ 1000 cm <SUP>−1</SUP>, ν<SUB>as</SUB>(SO<SUB>2</SUB>) ≈ 1150 cm <SUP>−1</SUP>). Investigations into the reactivity of <B>1</B> and <B>2</B> toward H<SUP>+</SUP> and oxygen atom transfer reagents have led to a mechanism for sulfur oxidation in which <B>2</B> could form even in the absence of base but is rapidly protonated to yield an oxoiron(IV) species with an uncoordinated thiol moiety that acts as both oxidant and substrate in the conversion of <B>2</B> to <B>3</B>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2010/jacsat.2010.132.issue-48/ja1045428/production/images/medium/ja-2010-045428_0015.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja1045428'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja1045428'>ACS Electronic Supporting Info</A></P>
McDonald, ThomasM.,Lee, Woo Ram,Mason, Jarad A.,Wiers, Brian M.,Hong, Chang Seop,Long, Jeffrey R. American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.16
<P>Two new metal organic frameworks, M-2(dobpdc) (M = Zn (1), Mg (2); dobpdc(4-) = 4,4'-dioxido-3,3'-biphenyldicarboxylate), adopting an expanded MOF-74 structure type, were synthesized via solvothermal and microwave methods. Coordinatively unsaturated Mg2+ cations lining the 18.4-angstrom-diameter channels of 2 were functionalized with N,N'-dimethylethylenediamine (mmen) to afford Mg-2(dobpdc)-(mmen)(1.6)(H2O)(0.4) (mmen-Mg-2(dobpdc)). This compound displays an exceptional capacity for CO2 adsorption at low pressures, taking up 2.0 mmol/g (8.1 wt %) at 0.39 mbar and 25 degrees C, conditions relevant to removal of CO2 from air, and 3.14 mmol/g (12.1 wt %) at 0.15 bar and 40 degrees C, conditions relevant to CO2 capture from flue gas. Dynamic gas adsorption/desorption cycling experiments demonstrate that mmen-Mg-2(dobpdc) can be regenerated upon repeated exposures to simulated air and flue gas mixtures, with cycling capacities of 1.05 mmol/g (4.4 wt %) after 1 h of exposure to flowing 390 ppm CO2 in simulated air at 25(degrees)C and 2.52 mmol/g (9.9 wt %) after 15 min of exposure to flowing 15% CO2 in N-2 at 40 degrees C. The purity of the CO2 removed from dry air and flue gas in these processes was estimated to be 96% and 98%, respectively. As a flue gas adsorbent, the regeneration energy was estimated through differential scanning calorimetry experiments to be 2.34 MJ/kg CO2 adsorbed. Overall, the performance characteristics of mmen-Mg-2(dobpdc) indicate it to be an exceptional new adsorbent for CO2 capture, comparing favorably with both amine-grafted silicas and aqueous amine solutions.</P>
Korea's Growth and Her International Relations
McDonald.Donald S 연세대학교 동서문제연구소 1986 東西硏究 JOURNAL OF EAST AND WEST STUDIES Vol.15 No.2
In conclusion, let me summarize the points I have made. The modern international order can be visualized as a system in which the many national actors relate to one another by mutual demands and responses. Each state, by applying its own levers of national power and capability, seeks to maximize its benefits in this interplay of demands and responses. in doing so, hewever, it must concern itself not only with its own needs and internal equilibrium, but also with international equilibrium.
( Iryna Mcdonald ),( Rudra Baral ),( Doohong Min ) 한국축산학회(구 한국동물자원과학회) 2021 한국축산학회지 Vol.63 No.2
Alfalfa (Medicago sativa L.) is an important forage legume grown in Kansas, USA and its productivity with cool-season grasses however is unknown. The objective of this study was to determine the dry matter yield (DMY) and forage nutritive value of alfalfa-grass mixtures compared to those of alfalfa and grasses grown in monoculture with and without nitrogen fertilization. Three different alfalfa varieties were planted (reduced-lignin alfalfa, Roundup Ready, and conventional alfalfa) and two kinds of cool-season grasses (smooth brome, Bromus inermis Leyss, and tall fescue, Festuca arundinacea Schreb) were planted as a monoculture or in alfalfa-grass mixtures. Nitrogen fertilizer (urea) was applied at green-up at a rate of 56 kg/ha and after the second cutting at a rate of 56 kg/ha in 2016 and 2017, respectively. and control treatments received no nitrogen. DMY was significantly higher in monoculture alfalfa and alfalfa-grass mixtures than in grass monocultures. Between alfalfa monoculture and alfalfa-grass mixtures, no significant differences in DMY were found. For all treatments, nitrogen application significantly increased DMY compared to the control. In 2016 and 2017, the low-lignin alfalfa monoculture had the lowest acid detergent fiber (ADF) and the grass monocultures had the highest ADF. In 2016 and 2017, neutral detergent fiber (NDF) in smooth bromegrass and tall fescue was higher than in other species treatments. A low-lignin alfalfa monoculture had significantly lower NDF concentration compared to alfalfa-grass mixtures. When averaged over 2016 and 2017, relative feed value (RFV) was highest in low-lignin alfalfa and lowest in the grass monocultures. In both years, nitrogen fertilizer application did not affect nutritive values.