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May 21

by ZFreixa in publications, Quimica, Sin categoría 0 comments

Photoswitchable catalysis using organometallic complexes

A mini-review on Photoswitchable catalysis with organometallic compounds. This review describes the state of the art in photoswitchable organometallic catalysis, underlining the importance of ligand design. The implementation of spatio-temporal control on known catalytic processes has been appealing to several researchers for a long time. Even though the area is still in its infancy, the diversity of the existing examples shows that there are plenty possibilities in terms of the photochromic actuator of choice, and on the expected effect of the photochemical transformation on the catalytic process. The pioneering examples discussed here are, in many cases, just basic models far from efficient. However, they suffice to envisage the magnitude of the space that remains unexplored, letting us foresee that exciting innovations are awaiting. To access publication click here.

May 21

by ZFreixa in publications, Quimica, Sin categoría 0 comments

Proton-responsive Ruthenium(II) Catalysts for the Solvolysis of Ammonia-Borane

Our work on a proton-responsive hydrogen generation catalyst reached the cover in Organometallics! Two water-soluble ruthenium(II) complexes (1 and 2) containing the proton-responsive 6,6′-dihydroxy-2,2′-bipyridine (dhbp) ligand were studied as precatalysts for the solvolysis of ammonia-borane (AB) in water and/or alcohols. Both precursors generate in situ the same catalytic system. In spite of the excellent initial activities observed, it suffered a sudden deactivation at extended conversions. Detailed experimental studies combined with theoretical (density functional theory) calculations permitted us to describe the reaction mechanism as two interrelated pH-dependent catalytic cycles operating within a single run. According to this hypothesis, the deactivation observed occurred as a consequence of the increase in NH3 concentration and pH along the reaction progress. It was attributed to deprotonation of the dhbp ligand and amination or hydroxylation of the resulting compound. Accordingly, reactions performed in buffered solutions at neutral pH retarded this process, and up to 2.5 equiv of H2 per mole of AB were liberated in less than 1 min (TOF50% up to 33 113 h–1 (TOF = turnover frequency)). When the reaction was run in alcohols (MeOH, EtOH, or iPrOH) it proceeded at faster rates than in water, the one discussed here being the first homogeneous catalytic system active […]

Mar 17

by ZFreixa in Sin categoría 0 comments

Photo-tunable hydrogen generation

Our first example of a photo-controled catalyst for hydrogen generation from ammonia-borane just published in Dalton Transactions. Eight new ruthenium(II) half-sandwich complexes containing azobenzene-appended pyridine (1), bipyridine (2–5) and phosphine (6 and 7) ligands have been synthesized and fully characterized. UV-vis spectroscopic studies showed that the trans-to-cis photoisomerization was strongly inhibited upon coordination to the metal centre in azopyridine-derived ligands 1 and 2, but it remained efficient in azobenzene-appended bipyridine (3–5) and phosphine (6 and 7) ligands. The complexes were tested as precatalysts for photo-controlled hydrogen generation by hydrolytic decomposition of ammonia-borane (AB). In situ irradiation of the reaction mixtures of compounds [Ru(p-Cym)(6)Cl]Cl and [Ru(p-Cym)(7)Cl]Cl induced a clear change in the catalytic reaction rate, serving as a proof of concept for light-controlled hydrogen generation.

Feb 04

by ZFreixa in Meetings, People, Quimica, seminar, Sin categoría, Zoraida 0 comments tags: lectures, Meetings, seminars, UAB, Zoraida

Seminar at UAB

It was a nice day, meeting friends and colleagues. Thanks for the invitation!

Sep 16

by FreixaGroup in Metales, Nature, Quimica, Sin categoría 0 comments

Ainara’s PhD Defence

Ainara Telleria defended her PhD on 22nd July 2016. She was awarded Doctor Cum Laude with International Mention.

Sep 25

by ZFreixa in Entrevista, Quimica, Sin categoría, Zoraida 0 comments tags: Entrevista, Investigación, Química, Universidad, Zoraida

En el mapa de la ciencia

Muchos no se conocen, pero cuando el fotógrafo les pide que hablen entre ellos para parecer más naturales no lo dudan ni un momento y comienzan a conversar como viejos amigos. Es como si tuvieran algo en común y ciertamente lo tienen, porque las ocho personas que se han citado en el centro Joxe Mari Korta para participar en una sesión fotográfica son investigadores. Faltan dos que no han podido acudir al encuentro por motivos de trabajo pero no por ello dejarán de salir en estas páginas. Son diez investigadores del más alto nivel que han venido a trabajar a Gipuzkoa atraídos por la fundación Ikerbasque y forman parte del grupo de 125 personas procedentes de veinte países que se han incorporado de forma permanente a las universidades y centros de investigación del País Vasco. Su aportación se puede medir de forma económica ya que, según la fundación, los científicos contratados por Ikerbasque han logrado un retorno para Euskadi de 17,5 millones de euros, lo que supone que por cada euro invertido por el Gobierno Vasco en esta entidad se obtienen dos euros. Es una aportación importante pero, sobre todo, estos diez investigadores que se dedican a ramas tan diversas […]