Publications 2011

2011

“In silico” mechanistic studies as predictive tools in microwave-assisted organic synthesis.

A M Rodriguez, P Prieto, A de la Hoz, A Díaz-Ortiz. 

Computational calculations can be used as a predictive tool in Microwave-Assisted Organic Synthesis (MAOS). A DFT study on Intramolecular Diels-Alder reactions (IMDA) indicated that the activation energy of the reaction and the polarity of the stationary points are two fundamental parameters to determine “a priori” if a reaction can be improved by using microwave irradiation. –

Org. Biomol. Chem., 2011, 9, 2371-2377

Highly Conductive Redox Protein–Carbon Nanotube Complex for Biosensing Applications

Chiara Baldacchini, Maria Antonia Herrero Chamorro, Maurizio Prato, Salvatore Cannistraro. The integration of redox proteins with nanomaterials has attracted much interest in the past years, and metallic single-walled carbon nanotubes (SWNTs) have been introduced as efficient electrical wires to connect biomolecules to metal electrodes in advanced nano-biodevices. Besides preserving biofunctionality, the protein–nanotube connection should ensure appropriate molecular orientation, flexibility, and efficient, reproducible electrical conduction. In this respect, yeast cytochrome c redox proteins are connected to gold electrodes through lying-down functionalized metallic SWNTs. Immobilization of cytochromes to nanotubes is obtained via covalent bonding between the exposed protein thiols and maleimide-terminated functional chains attached to the carbon nanotubes. A single-molecule study performed by combining scanning probe nanoscopies ascertains that the protein topological properties are preserved upon binding and provides unprecedented current images of single proteins bound to carbon nanotubes that allow a detailed IVcharacterization. Collectively, the results point out that the use as linkers of suitably functionalized metallic SWNTs results in an electrical communication between redox proteins and gold electrodes more efficient and reproducible than for proteins directly connected with metal surfaces. – Advanced Functional Materials, 2011, 1, 153–157.

Ball Milling modification of Single-Wall Carbon Nanotubes: purification, cutting and functionalization

N. Rubio, C. Fabbro, M. A. Herrero, A. de la Hoz, M. Meneghetti, J. L. G. Fierro, M. Prato, E. Vázquez. Single-walled carbon nanotubes (SWNTs) can be successfully cut with relatively homogeneous sizes using a planetary mill. The optimized conditions produce highly dispersible SWNTs that can be efficiently functionalized in a variety of synthetic ways. As clearly shown by Raman spectroscopy, the milling/cutting procedure compares very favorably with the most common way of purifying SWNTs, namely, treatment with strong oxidizing acids. Moreover a similar milling process can be used to functionalize and cut pristine SWNTs by one-step nitrene chemistry.- Small, 2011, 7, 665-674.

Influence of Polarity on the Scalability and Reproducibility of Solvent-Free Microwave-Assisted Reactions

Ángel Diaz-Ortiz, Antonio de la Hoz, Jesus R. Alcazar,  Jose; A. Carrillo, Maria Herrero, Alberto Fontana,  Juan de M. Munoz, Pilar Prieto, Abel de Cozar. Organic reactions performed in the absence of solvent in domestic ovens without appropriate temperature control are generally considered as not reproducible, particularly when different instruments are used. For this reason, reproducibility has historically been one of the major issues associated with Microwave-Assisted Organic Synthesis (MAOS) especially when domestic ovens are involved. The lack of reproducibility limits the general applicability and the scale up of these reactions. In this work several solvent-free reactions previously carried out in domestic ovens have been translated into a single-mode microwave reactor and then scaled up in a multimode oven. The results show that most of these reactions, although not considered as reproducible, can be easily updated and applied in microwave reactors using temperature-controlled conditions. Furthermore, computational calculations can assist to explain and/or predict whether a reaction will be reproducible or not. –

Combinatorial Chemistry & High Throughput Screening, 2011, 14, 2, 109-116.

Study of the Proteolytic and Lipolytic Processes in Manchego Cheese by NMR.

M. Moreno, A. Moreno, M. V. Gómez, J. M. Poveda, L. Cabezas.

Magnetic Resonance in Food Science: An Exciting Future. 2011, 52, 54-59. RSC.

Quality Markers of Red Wines from Spanish Region of Castilla-La Mancha Using Nuclear Magnetic Resonance.

A. Moreno, L. F. Labrador, M. Moreno, M. S. Pérez, M. A. González, E. M. Sánchez-Palomo, J. M. Lemus.

Magnetic Resonance in Food Science: An Exciting Future. 2011, 52, 60-67. RSC.

Comparative Study of the Thermal and Microwave Oxidation in Olive Oil. 31p-Nmr Quantitative Determination Of 1,2 And 1,3-Diglycerides And Other Minor Compounds.

C. Lucas-Torres, M. Moreno, A. Juan, A. de la Hoz, A. Moreno.

Magnetic Resonance in Food Science: An Exciting Future. 2011, 52, 100-104. RSC.

Rapid Quantitative Determination by 13C-NMR of the Composition of Acetylglycerol Mixtures as Byproduct in Biodiesel Synthesis.

A. Casas, C. Lucas-Torres. A. Moreno, A. Pérez, M. J. Ramos, A. Simón.

Fuel, 2012, 92, 180-186

Synthesis and Characterization of Metallodendritic Palladium-Biscarbene Complexes Derived from 1,1′-Methylenebis(1,2,4-triazole).

Valentín Hornillos, Javier Guerra, Abel de Cózar, Pilar Prieto, Sonia Merino, Miguel A. Maestro, Enrique Díez-Barra and Juan Tejeda. The syntheses of first generation dendritic compounds bearing 1,1′-alkane-1,1-diylbis(4-butyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene)palladium(II) dibromide on the periphery are described. The metallabiscarbene moieties have also been studied separately from the dendrimer. These compounds display a non-symmetric boat-to-boat conformational equilibrium that has axial and equatorial arrangements. The predominance of the axial conformer in the equilibrium is supported by DFT calculations. The X-ray solid state structures of axial conformers of 3-hydroxy- and 3-mesyloxy-1,1′-propane-1,1-diylbis(4-butyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene)palladium(II) dibromide are reported. These complexes display modest catalytic activity in the Heck reaction with activated aryl bromides and the dendritic catalysts were more active than the corresponding non-dendritic mononuclear species, a finding indicative of a cooperative effect.

Dalton Trans., 2011, 40, 4095-4103

Reproducibility and Scalability of Microwave Assisted Reactions: From Domestic ovens to Continuous Flow Systems.

J. Alcázar, A. de Cózar, A. de la Hoz, A. Díaz-Ortiz, J. R. Carrillo, M. A. Herrero, J. M. Muñoz, P. Prieto.

Microwave Heating ISBN 978-953-307-325-5. InTech. 2011, 137-162.

Substitution Reactions in Green Chemistry.

A. de la Hoz, A. Díaz-Ortiz. Handbook of Green Chemistry. Oxford University Press. in press.

Application of Flow Chemistry to the Reduction of Nitriles to Aldehydes.

J. de Mata Muñoz, J. Alcázar, A. Diaz-Ortiz; A. de la Hoz.

Reduction of nitriles to aldehydes with diisobutylaluminium hydride (DIBAL-H) is an important transformation in organic chemistry. But the use of this reaction is limited for the lack of reproducibility due to the instability of the intermediates formed. In the current article we disclose the improvement of the reaction applying continuous flow technology.

Tetrahedron Lett., 2011, 52, 6058-6060

Few-layer graphenes using melamine and ball milling processing.

V.  León, M. Quintana, M. A. Herrero, J. L. G. Fierro, A. de la Hoz, M. Prato, E. Vázquez.

We report a simple, practical scalable procedure to produce few-layer graphene sheets using ball-milling. Commercially available melamine can be efficiently used to exfoliate graphite and generate concentrated water or DMF dispersions. Chem. Commun., 2011, 47, 10936-10938

Electrochemical synthesis and spectroelectrochemical characterization of triazole/thiophene conjugated polymers

F. Montilla,  F. Huerta, D. Salinas-Torres, E. Morallón, C. Cebrián, P. Prieto, Á. Díaz-Ortiz, A. de la Hoz, J.R. Carrillo, C. Romero. 

Novel electropolymerizable monomers based on triazole–thiophene units were characterized by both spectroscopic and electrochemical methods. It was found that those monomers which were enriched with additional thiophene units in their chemical structure showed red-shifted electronic transitions and lower oxidation potentials when compared with the short-chain disubstituted triazole monomer. The monomers studied were electropolymerized in organic medium giving rise to their corresponding electroactive polymers. These materials can be p-doped at potentials values which can be properly correlated with the thiophene conjugation length of the parent precursor. As a general rule, it was observed that the longer the conjugation length, the lower the HOMO level. Only the alternating bisthiophene–triazole polymer, poly-TTT, can be both p- and n-doped within the electrochemical window of the solvent employed. The doping processes are characterized by the formation of charge traps that avoid the reversible recovery of the injected charge. In addition, polaronic species formed upon electrochemical doping seem to be at the origin of the electronic transition bands observed for all the materials in the visible low-frequency to near-infrared optical range.

Electrochim. Acta. 2011, 58, 215-222.

Charge Transfer Events in Semiconducting Single-Wall Carbon Nanotubes

C. Oelsner, M. A. Herrero, C. Ehli, M. Prato, D.M. Guldi

Electron-donating ferrocene units have been attached to SWNTs, with different degrees of functionalization. By means of a complementary series of novel spectroscopic techniques (i.e., steady-state and time-resolved), we have documented that mutual interactions between semiconducting SWNT and the covalently attached electron donor (i.e., ferrocene) lead, in the event of photoexcitation, to the formation of radical ion pairs. In the accordingly formed radical ion pairs, oxidation of ferrocene and reduction of SWNT were confirmed by spectroelectrochemistry. It is, however, shown that only a few semiconducting SWNTs [i.e., (9,4), (8,6), (8,7), and (9,7)] are susceptible to photoinduced electron transfer processes. These results are of relevant importance for the development of SWNT-based photovoltaics.

J. Am. Chem. Soc. 2011, 133, 18696–18706

Functional motor recovery from brain ischemic insult by carbon nanotube-mediated siRNA silencing

K.T. Al-Jamal, L. Gherardini, G. Bardi, A. Nunes, C. Guo, C. Bussy, M.A. Herrero, A. Bianco, M. Prato, K. Kostarelos, T. Pizzorusso

Stroke is the second cause of death worldwide with ischemic stroke accounting for 80% of all stroke insults. Caspase-3 activation contributes to brain tissue loss and downstream biochemical events that lead to programmed cell death after traumatic brain injury. Alleviation of symptoms following ischemic neuronal injury can be potentially achieved by either genetic disruption or pharmacological inhibition of caspases. Here, we studied whether silencing of Caspase-3 using carbon nanotube-mediated in vivo RNA interference (RNAi) could offer a therapeutic opportunity against stroke. Effective delivery of siRNA directly to the CNS has been shown to normalize phenotypes in animal models of several neurological diseases. It is shown here that peri-lesional stereotactic administration of a Caspase-3 siRNA (siCas 3) delivered by functionalized carbon nanotubes (f-CNT) reduced neurodegeneration and promoted functional preservation before and after focal ischemic damage of the rodent motor cortex using an endothelin-1 induced stroke model. These observations illustrate the opportunity offered by carbon nanotube-mediated siRNA delivery and gene silencing of neuronal tissue applicable to a variety of different neuropathological conditions where intervention at well localized brain foci may offer therapeutic and functional benefits.

Proc. Natl. Acad. Sci. U. S. A. 2011, 108, 10952-10957

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