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Rational and Statistical Approaches in Enhancing the Yield of Ethylene Carbonate in Urea Transesterification with Ethylene Glycol over Metal Oxides

  • Fakhrnasova, Dina
  • Chimentão, Ricardo J.
  • Medina, Francisco
  • Urakawa, Atsushi
<p> This work employs (i) a rational approach to improve the material properties of catalysts for urea transesterification with ethylene glycol (EG) to ethylene carbonate (EC) over metal oxides and (ii) a statistical approach to maximize the desired product. For the rational approach, single- and mixed-metal oxides with different elemental combinations (Zn, Mg, Al, Fe) with a variety of acid&ndash;base properties were synthesized and evaluated for the reaction. The roles of acidity and basicity in the identified reaction paths were clarified on the basis of product selectivities and kinetic parameters extracted from the concentration profiles of reactants and products in every reaction path by means of in situ IR monitoring and subsequent multivariate analysis. The paths toward EC are favorably catalyzed by acidic sites, while basic sites catalyze all paths toward undesired products. However, the surface sites are blocked when the acidity is too high and there exists an optimum value for the ratio of total acidic and basic sites to be an efficient catalyst in the targeted reaction. A mixed-metal oxide consisting of Zn and Fe at a 3:1 atomic ratio was found to be the optimum catalyst with a well-balanced acid&ndash;base property. Furthermore, a design of experiments (DoE) approach was used to statistically identify critical reaction parameters and optimize them for the best Zn- and Fe-containing catalysts. These approaches successfully gave insights into the determining material factors for the reaction and afforded excellent EC selectivity (up to 99.6%) with high yield.</p>
Proyecto:


Simulating the Favorable Aggregation of Monolacunary Keggin Anions

  • Serapian, Stefano
  • Bo, Carles
<div class="page" title="Page 1"> <div class="layoutArea"> <div class="column"> <p> <span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">We here present a series of classical molecular dynamics simulations (MD) on aqueous solutions of the salts Li</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: -1.000000pt">5</span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">AlW</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: -1.000000pt">12</span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">O</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: -1.000000pt">40 </span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">and Li</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: -1.000000pt">9</span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">AlW</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: -1.000000pt">11</span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">O</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: -1.000000pt">39</span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">, providing us with valuable insight on their aggregative behaviour. Analysis of relative dipole moment orientation in pairs of aggregated [AlW</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: -1.000000pt">11</span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">O</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: -1.000000pt">39</span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">]</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: 5.000000pt">9- </span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">excludes that their large dipole moment is behind their greater propensity to aggregate. On the other hand, MD simulations of the aqueous Li</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: 5.000000pt">+ </span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">salt of the fictitious [AlW</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: -1.000000pt">12</span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">O</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: -1.000000pt">40</span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">]</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: 5.000000pt">9-</span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">&mdash;as high in charge as [AlW</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: -1.000000pt">11</span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">O</span><span style="font-size: 6.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic; vertical-align: -1.000000pt">39</span><span style="font-size: 10.000000pt; font-family: 'TimesNewRomanPS'; font-style: italic">]</span><span s
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Oxo-Bridge Scenario behind Single-Site Water-Oxidation Catalysts

  • López, Isidoro
  • Maji, Somnath
  • Benet-Buchholz, Jordi
  • Llobet, Antoni
<p> High-oxidation-state decay of mononuclear complexes [RuTB(H2O)]2+ (X2+, where B = 2,2&prime;-bpy or bpy for X = 1; B = 5,5&prime;-F2-bpy for X = 2; B = 6,6&prime;-F2-bpy for X = 3; T = 2,2&prime;:6&prime;,2&Prime;-terpyridine) oxidized with a large excess of CeIV generates a manifold of polynuclear oxo-bridged complexes. These include the following complexes: (a) dinuclear [TB-RuIV-O-RuIV-(T)(O)OH2]2+ (1-dn4+), [TB-RuIII-O-RuIII-T(MeCN)2]4+ (1-dn-N4+), and {[RuIII(trpy)(bpy)]2(&mu;-O)}4+(1-dm4+); (b) trinuclear {[RuIII(trpy)(bpy)(&mu;-O)]2RuIV(trpy)(H2O)}(ClO4)56+ (1-tr6+) and {[RuIII(trpy)(bpy)(&mu;-O)]2RuIV(pic)2}(ClO4)4 (1-tr-P4+, where P is the 2-pyridinecarboxylate anion); and (c) tetranuclear [TB-RuIII-O-TRuIV(H2O)-O-TRuIV(H2O)-O-RuIII-TB]8+ (1-tn8+), [TB-RuIII-O-TRuIV(AcO)-O-TRuIV(AcO)-O-RuIII-TB]6+ (1-tn-Ac6+), and [TB-RuII-O-TRuIV(MeCN)-O-TRuIV(MeCN)-O-RuII-TB]6+ (1-tn-N6+). These complexes have been characterized structurally by single-crystal X-ray diffraction analysis, and their structural properties were correlated with their electronic structures. Dinuclear complex 1-dm4+ has been further characterized by spectroscopic and electrochemical techniques. Addition of excess CeIV to 1-dm4+ generates dioxygen in a catalytic manner. However, resonance Raman spectroscopy points to the in situ formation of 1-dn4+ as the active species.</p>
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Highly Efficient Binuclear Ruthenium Catalyst for Water Oxidation

  • Sander, Anett C.
  • Maji, Somnath
  • Francàs, Laia
  • Böhnisch, Torben
  • S. Dechert, Sebastian
  • Llobet, Antoni
  • Meyer, Franc
<p> Water splitting is one of the key steps in the conversion of sunlight into a usable renewable energy carrier such as dihydrogen or more complex chemical fuels. Developing rugged and highly efficient catalysts for the oxidative part of water splitting, the water oxidation reaction generating dioxygen, is a major challenge in the field. Herein, we introduce a new, and rationally designed, pyrazolate-based diruthenium complex with the highest activity in water oxidation catalysis for binuclear systems reported to date. Single-crystal X-ray diffraction showed favorable preorganization of the metal ions, well suited for binding two water molecules at a distance adequate for O<img alt="[BOND]" height="6" src="file:///C:/Users/nmas/AppData/Local/Temp/msohtmlclip1/01/clip_image001.gif" width="17" />O bond formation; redox titrations as well as spectroelectrochemistry allowed characterization of the system in several oxidation states. Low oxidation potentials reflect the trianionic character of the elaborate compartmental pyrazolate ligand furnished with peripheral carboxylate groups. Water oxidation has been mediated both by a chemical oxidant (CeIV)&mdash;by means of manometry and a Clark electrode for monitoring the dioxygen production&mdash;and electrochemically with impressive activities.</p>
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Behavior of the Ru-bda Water Oxidation Catalyst Covalently Anchored on Glassy Carbon Electrodes

  • Matheu, Roc
  • Francàs, Laia
  • Chernev, Petko
  • Ertem, Mehmed
  • Batista, Victor
  • Haumann, Michael
  • Sala, Xavier
  • Llobet, Antoni
<p> Electrochemical reduction of the dizaonium complex, [RuII(bda)(NO)(N&ndash;N2)2]3+, 23+ (N&ndash;N22+ is 4-(pyridin-4-yl) benzenediazonium and bda2&ndash; is [2,2&prime;-bipyridine]-6,6&prime;-dicarboxylate), in acetone produces the covalent grafting of this molecular complex onto glassy carbon (GC) electrodes. Multiple cycling voltammetric experiments on the GC electrode generates hybrid materials labeled as GC-4, with the corresponding Ru-aqua complex anchored on the graphite surface. GC-4 has been characterized at pH = 7.0 by electrochemical techniques and X-ray absorption spectroscopy (XAS) and has been shown to act as an active catalyst for the oxidation of water to dioxygen. This new hybrid material has a lower catalytic performance than its counterpart in homogeneous phase and progressively decomposes to form RuO2 at the electrode surface. Nevertheless the resulting metal oxide attached at the GC electrode surface, GC-RuO2, is a very fast and rugged heterogeneous water oxidation catalyst with TOFis of 300 s&ndash;1 and TONs &gt; 45 000. The observed performance is comparable to the best electrocatalysts reported so far, at neutral pH.</p>
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Redox Non-innocent Ligand Controls Water Oxidation Overpotential in a New Family of Mononuclear Cu-Based Efficient Catalysts

  • Garrido-Barros, Pablo
  • Funes-Ardoiz, Ignacio
  • Drouet, Samuel
  • Benet-Buchholz, Jordi
  • Maseras, Feliu
  • Llobet, Antoni
<p> A new family of tetra-anionic tetradentate amidate ligands, N1,N1&prime;-(1,2-phenylene)bis(N2-methyloxalamide) (H4L1), and its derivatives containing electron-donating groups at the aromatic ring have been prepared and characterized, together with their corresponding anionic Cu(II) complexes, [(LY)Cu]2&ndash;. At pH 11.5, the latter undergoes a reversible metal-based III/II oxidation process at 0.56 V and a ligand-based pH-dependent electron-transfer process at 1.25 V, associated with a large electrocatalytic water oxidation wave (overpotential of 700 mV). Foot-of-the-wave analysis gives a catalytic rate constant of 3.6 s&ndash;1 at pH 11.5 and 12 s&ndash;1 at pH 12.5. As the electron-donating capacity at the aromatic ring increases, the overpotential is drastically reduced down to a record low of 170 mV. In addition, DFT calculations allow us to propose a complete catalytic cycle that uncovers an unprecedented pathway in which crucial O&ndash;O bond formation occurs in a two-step, one-electron process where the peroxo intermediate generated has no formal M&ndash;O bond but is strongly hydrogen bonded to the auxiliary ligand.</p> <p> &nbsp;</p>
Proyecto:


Backbone Immobilization of the Bis(bipyridyl)pyrazolate Diruthenium

  • Odrobina, Jann
  • Scholz, Julius
  • Pannwitz, Andrea
  • Francàs, Laia
  • Dechert, Sesbastian Llobet, Antoni
  • Jooß, Christian
  • Meyer, Freanc
<p> Efficient catalysts for water oxidation are key to all scenarios for artificial solar water splitting, and, in the case of molecular catalysts, their immobilization on conductive solid supports is considered essential for the construction of a photoelectrochemical cell. In this work, derivatives of the rugged 3,5-bis(bipyridyl)pyrazolate (bbp)-based diruthenium water oxidation precatalyst [(&mu;-bbp){Ru(py)2}2(&mu;-X)]2+ (X = OAc, CO3H) have been synthesized that are equipped with a carboxylate anchor at the ligand backbone. The para-C6H4COOR (R = Et, H) substituent at the pyrazolate-C4 is shown to not have any significant effect on the electronic properties of the bbp-based diruthenium core, or on the catalytic performance when using CeIV as a chemical oxidant. The bbp-based complex with labile exogenous bicarbonate bridge (4) has been successfully anchored on mesoporous ITO (mesoITO), and the hybrid ITO
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N-Iodosuccinimide promoted Hofmann-Löffler Reactions of Sulfonimides under Visible Light

  • O’Broin, Calvin Q.
  • Fernández, Patricia
  • Martínez, Claudio
  • Muñiz, Kilian
<p> Conditions for an attractive and productive protocol for the position-selective intramolecular C-H amination of aliphatic groups (Hofmann-L&ouml;ffler reaction) are reported employing sulfonimides as nitrogen sources. <em>N</em>-Iodosuccinimide is the only required promoter for this transformation, which is conveniently initiated by visible light. The overall transformation provides pyrrolidines under mild and selective conditions as demonstrated for 17 different substrates.</p>
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Indoline as electron donor unit in ‘‘Push–Pull’’ organic small molecules for solution processed organic solar cells: Effect of the molecular p-bridge

  • Montcada, Núria F.
  • Cabau, Lydia
  • Kumar, Challuri Vijay
  • Cambarau, Werther
  • Palomares, Emilio
<div> In this work we have synthesized and characterized four indoline-based small organic molecules</div> <div> for their use as electron donor moiety in bulk-heterojunction solution processed</div> <div> organic solar cells combined with PC70BM as electron acceptor. Our results show a wide</div> <div> range of light to energy efficiencies from 0.8% to 3.5% under standard measurement conditions.</div> <div> An initial analysis suggests that the main limitation is the device photocurrent due to</div> <div> the device film thickness. Yet, charge transfer dynamics were studied to correlate charge</div> <div> loss mechanisms to p-bridge structural variations and, moreover, mobility measurements</div> <div> were also carried out to fully explain these device limitations.</div>
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