Atom transfer reactions of high-valent chromium and manganese porphyrins

The terminally bound nitrido ligand of manganese(V) porphyrin complexes serves as a good bridging species in electron transfer processes. Thus, the nitrogen atom of a porphyrinatomanganese nitrido complex was reversibly transferred to porphyrinatomanganese(II), in a formal three-electron redox process. Evidence is presented that supports an inner-sphere mechanism for this process. The coordinating solvent, tetrahydrofuran, decreased the rate constant for this reaction by three orders of magnitude compared to that observed in the noncoordinating solvent, toluene. The number of redox equivalents exchanged in nitrogen atom transfer processes can be varied from three to two by choosing the appropriate reductant such as a porphyrinatomanganese(III) chloride complex. Evidence is presented to support a mechanism for the reaction between porphyrinatomanganese nitride and porphyrinatomanganese chloride which involves prior dissociation of the chloride ion before the formation of a [mu]-nitrido species. Thus when given a choice of potential bridging ligands (eg. N vs Cl or pivalate) the multi-electron process studied here preferentially selects the nitrido ligand;The terminally bound oxo ligand of chromium porphyrin complexes has also been shown to also serve as a good bridging ligand in electron transfer processes. It was demonstrated that a one-electron transfer involving complete atom transfer was possible by choosing the correct redox partner, a porphyrinatochromium(III) complex. The mechanism for this reaction has been shown to proceed through a [mu]-oxo species. Unlike the mechanism for porphyrinatomanganese chloride, the porphyrinatochromium chloride complex does not require prior dissociation of the chloride ion. The rate constant was not decreased by addition of a ten fold excess of chloride ion

Oxygen Atom Transfer Reactions of Chromium Porphyrins: An Electronic Rationale for Oxo Transfer versus μ-Oxo Product Formation

Treatment of (meso-tetra-p-tolylporphyrinato)chromium(IV) oxide, {TTP)Cr=O, with (octaethylporphyrinato)chromium( III) chloride, (OEP)Cr-Cl, in benzene results in the reversible exchange of axial ligands to form (TTP)Cr-Cl and (OEP)Cr=O. The net result is a formal one-electron redox process. This occurs with a second-order rate constant of 0.14 :1:: 0.01 M-1 s-1 to form an equilibrium mixture with K = 2.7 :1:: 0.1 at 30 °C (ill/* = 15.4 :1:: 0.7 kcaljmol, M* = -12 :1:: 2 cal/ (mol·K), ill/0 = -2.0 :1:: 0.4 kcaljmol, and M 0 = -4.6 :1:: 1.2 cal/ (mol·K)). Use of pivalate in place of chloride on the Cr(III) complex causes no significant change in the rate of this one-electron redox process. The sterically protected Baldwin\u27s C2-capped {porphyrinato)chromium(III) complex, (CAP)Cr-Cl, also undergoes oxygen atom transfer with (OEP)Cr=O at a similar rate. In addition, excess chloride inhibits the rate of oxygen transfer with chlorochromium(III) complexes. These results support an inner-sphere mechanism involving a ~-oxo intermediate which is formed after an initial ligand (chloride or pivalate) dissociation from the chromium(III) reductant

Thermodynamic and Kinetic Aspects of Two- and Three-Electron Redox Processes Mediated by Nitrogen Atom Transfer

Treatment of (meso-tetra-p-tolylporphyrinato)manganese(V) nitride, (TTP)Mn==N, with (octaethylporphyrinato) manganese(II), Mn(OEP), in toluene leads to the reversible transfer of the nitrido ligand between the two metal complexes to form (OEP)Mn Nand Mn(TTP). The net result is a formal three-electron reduction of (TTP)MnvN to (TTP)Mn11• This occurs with a second-order rate constant of (5.6 ± 1.2) X 103 M-1 s-1 to form an equilibrium mixture with K~ = 1.2 ± 0.5 at 20 °C. The thermodynamic and activation parameters for this process are t:.H0 = 2.0 ± 0.2 kcalfmol, t:.S = 7 .I ± 0.6 calfmol·K, t:.H* = 9.4 ± 0.7 kcal/mol, and t:.S* = -10 ± 2 cal/mol·K. In THF at 20 °C, the equilibrium constant is 1.8 ± 0.2 and the rate constant drops to 2.3 ± 0.3 M-1 s-1• When a manganese(III) porphyrin complex is used as a reductant, reversible nitrogen atom transfer still occurs but mediates a formal two-electron process. At 22 °C, the exchange process between (TTP)MnCI and (OEP)Mn==N produces (TTP)Mn==N and (OEP)MnCI with a second-order rate constant of 0.010 ± 0.007 M-1 s-1 (t:.H* = 19 ± 2 kcal/mol and t:.S* = -3 ± 6 cal/mol·K) and forms an equilibrium mixture with Keq = 24.3 ± 3.3 (t:.H 0 = -7.0 ± 0.6 kcal/mol and t:.S 0 = -17 ± 2 cal/mol·K). Evidence for the formation of a binuclear wnitrido intermediate is presented for both processes. For the two-electron redox reaction, kinetic studies and mechanistic probes support a pathway which involves an initial chloride dissociation from the Mn(III) complex. Nitrogen atom transfer subsequently occurs between the Mn==N complex and the four-coordinate Mn(III) cationic species

The Grizzly, December 7, 2000

Football Coach Quits Amid Controversy • Field House Opening Postponed Until New Millennium • Ursinus\u27 Class of 2004 Survives Fall Semester • Finals Schedule • Holidays a Time for Giving at Ursinus • Islam Awareness Week Offers Cultural Insight • Students Experience Christmas in the Big Apple • Opinions: Campus Construction an Eyesore; UC Democrats Respond to Allegations; Grizzly a Success This Semester • First Annual Palooza a Poetic Success • Choir Angelic in Annual Coming of \u27Messiah\u27 • Hypnotist Anthony Entrances UC Students • Lady Bears Down, but not out • UC Swim Teams Suffer Defeat in Poolside Duels Against Archrivals • Wrestling Finishes 3rd at Invitational • Swarthmore Cuts Football, Wrestling, Badminton Programs • Pro Wrestlers Rumble on UC Campus • Barrett Breaks Scoring Record, Leads Bears to 3-2https://digitalcommons.ursinus.edu/grizzlynews/1481/thumbnail.jp

The Lantern Vol. 68, No. 1, Fall 2000

• In Attempting to Imitate J. Agard (III) • Headstones • Calligraphy Grace • Fifty Years • Morning • The Millstone • Quick Stop-Off • Jesus Wept (SuperBuick Bodybag) • Just a God • Amy • Silver Doubloons • Ogbanje • Left Behind • Asymmetrical Smile • Sundays • Pie in the Sky • No Surprises • Bill Gooden\u27s Son • Downcast Eyes Meet Tablecloth • Wetlands • Desperate Actions • Receiving End • A Pack of Matches • Coffeehttps://digitalcommons.ursinus.edu/lantern/1157/thumbnail.jp

The Lantern Vol. 68, No. 1, Fall 2000

• In Attempting to Imitate J. Agard (III) • Headstones • Calligraphy Grace • Fifty Years • Morning • The Millstone • Quick Stop-Off • Jesus Wept (SuperBuick Bodybag) • Just a God • Amy • Silver Doubloons • Ogbanje • Left Behind • Asymmetrical Smile • Sundays • Pie in the Sky • No Surprises • Bill Gooden\u27s Son • Downcast Eyes Meet Tablecloth • Wetlands • Desperate Actions • Receiving End • A Pack of Matches • Coffeehttps://digitalcommons.ursinus.edu/lantern/1157/thumbnail.jp

Dietary creatine supplementation in gilthead seabream (Sparus aurata) increases dorsal muscle area and the expression of myod1 and capn1 genes

Creatine (Cr) is an amino acid derivative with an important role in the cell as energy buffer that has been largely used as dietary supplement to increase muscle strength and lean body mass in healthy individuals and athletes. However, studies in fish are scarce. The aim of this work is to determine whether dietary Cr supplementation affects muscle growth in gilthead seabream (Sparus aurata) juveniles. Fish were fed ad libitum for 69 days with diets containing three increasing levels of creatine monohydrate (2, 5, and 8%) that were compared with a non-supplemented control (CTRL) diet. At the end of the trial, the fast-twist skeletal muscle growth dynamics (muscle cellularity) and the expression of muscle-related genes were evaluated. There was a general trend for Cr-fed fish to be larger and longer than those fed the CTRL, but no significant differences in daily growth index (DGI) were registered among dietary treatments. The dorsal cross-sectional muscle area (DMA) of fish fed Cr 5 and Cr 8% was significantly larger than that of fish fed CTRL. The groups supplemented with Cr systematically had a higher relative number of both small-sized (= 20)mu m). Dorsal total fibers number was highest in fish fed 5% Cr. In fish supplemented with 5% Cr, the relative expression of myogenic differentiation 1 (myod1) increased almost four times compared to those fed the CTRL diet. The relative expression of calpain 3 (capn3) was highest in fish fed diets with 2% Cr supplementation, but did not differ significantly from those fed the CTRL or Cr 5%. The myod1 gene expression had a positive and significant correlation with that of capn1, capnsla, and capn3 expression. These results suggest that the observed modulation of gene expression was not enough to produce a significant alteration in muscle phenotype under the tested conditions, as a non-significant increase in muscle fiber diameter and higher total number of fiber was observed, but still resulted in increased DMA. Additional studies may be required in order to better clarify the effect of dietary Cr supplementation in fish, possibly in conjunction with induced resistance training.project AQUAVALOR Development of a farmed fish as a functional food: Natural nutrient fortification and allergenic potential reduction, PROMAR - Projeto Piloto 31-03-05-FEP-0060 ValorMar Valorizacao integral dos recursos marinhos: potencial, inovacao tecnologica e novas aplicacoes, (Mobilizing R&TD Programs, Portugal 2020) - European Regional Development Fund (ERDF) 24517 10/SI/2016 European Social Fund (ESF) Fundacao para a Ciencia e Tecnologia (Portugal) PD/BDE/114436/2016 FCT - Foundation for Science and Technology UID/Multi/04326/2019info:eu-repo/semantics/publishedVersio

Spatially explicit analysis identifies significant potential for bioenergy with carbon capture and storage in China

As China ramped-up coal power capacities rapidly while CO2 emissions need to decline, these capacities would turn into stranded assets. To deal with this risk, a promising option is to retrofit these capacities to co-fire with biomass and eventually upgrade to CCS operation (BECCS), but the feasibility is debated with respect to negative impacts on broader sustainability issues. Here we present a data-rich spatially explicit approach to estimate the marginal cost curve for decarbonizing the power sector in China with BECCS. We identify a potential of 222 GW of power capacities in 2836 counties generated by co-firing 0.9 Gt of biomass from the same county, with half being agricultural residues. Our spatially explicit method helps to reduce uncertainty in the economic costs and emissions of BECCS, identify the best opportunities for bioenergy and show the limitations by logistical challenges to achieve carbon neutrality in the power sector with large-scale BECCS in China