Browsing by Subject "Dynamics"

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    Mechanically interlocked molecules in metal–organic frameworks
    (Royal Society of Chemistry, 2022-05-25) Saura-Sanmartin, Adrian; Pastor Vivero, Aurelia; Martinez-Cuezva, Alberto; Cutillas-Font, Guillermo; Alajarín, Mateo; Berná Cánovas, José; Química Orgánica
    Mechanically interlocked molecules (MIMs) have great potential in the development of molecular machinery due to their intercomponent dynamics. The incorporation of these molecules in a condensed phase makes it possible to take advantage of the control of the motion of the components at the macroscopic level. Metal–organic frameworks (MOFs) are postulated as ideal supports for intertwined molecules. This review covers the chemistry of the mechanical bond incorporated into metal–organic frameworks from the seminal studies to the latest published advances. We first describe some fundamental concepts of MIMs and MOFs. Next, we summarize the advances in the incorporation of rotaxanes and catenanes inside MOF matrices. Finally, we conclude by showing the study of the rotaxane dynamics in MOFs and the operation of some stimuli-responsive MIMs within MOFs. In addition to emphasising some selected examples, we offer a critical opinion on the state of the art of this research field, remarking the key points on which the future of these systems should be focused.
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    Modulating the catalytic activity by the mechanical bond: organocatalysis with polyamide [2]rotaxanes bearing a secondary amino function at the thread
    (Royal Society of Chemistry, 2022-04-06) Pérez Martínez, Jesús de María; Alajarín, Mateo; Martinez-Cuezva, Alberto; Berná Cánovas, José; Química Orgánica
    The modulation of the catalytic activity of degenerate succinamide-based [2]rotaxanes by changes at their macrocyclic component is disclosed herein. These systems, bearing an acyclic secondary amine function at the thread as the active site and incorporating different polyamide macrocycles, were evaluated as organocatalysts in iminium- and enamine-type processes. The results of kinetic studies clearly show a drastic variation of their catalytic efficiency, which apparently correlated with the electronics and dynamics of the entwined macrocycle.
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    Modulating the shuttling motion of [2]rotaxanes built of p-xylylenediamine units through permethylation at the benzylic positions of the ring
    (Royal Society of Chemistry, 2023-11-03) Puigcerver, Julio; Alajarín, Mateo; Berna, José; Martínez Cuezva, Alberto; Química Orgánica
    In this study, we show the effect of the gem-dimethyl substitution at the four benzylic carbons of the ring on the internal dynamics of two-station [2]rotaxanes. Such structural modification of the polyamide macrocycles promotes a drastic change of the internal dynamics as shown by variable-temperature (VT) 1H NMR experiments. We determined that the shuttling rates of the octamethylated macrocycle along a series of symmetrical threads were significantly faster compared to the non-substituted ring. This effect was particulary pronounced in the -based system, in which the rate was 27 times faster than that of the model system.
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    Trabajo y enfermedad : relaciones en litigio (España, siglo XX)
    (Universidad de Murcia, Servicio de Publicaciones, 2022) Cohen, Arón; Fleta, Agustín
    El concepto de accidente de trabajo, y aún más el de enfermedad profesional, no designan realidades que se impongan invariablemente por su sola denominación. El reconocimiento de un “nexo” entre trabajo y enfermedades ha sido en todas partes mucho más tímido y dificultoso que el de los accidentes propiamente dichos. Con el objetivo puesto en los riesgos de enfermar “con ocasión o por consecuencia del trabajo”, una muestra de un millar de sentencias judiciales, repartidas entre 1936 y 1983, comprueba el peso de inercias estructurales y se detiene en los signos de inflexión, en función de la evolución de la legislación de referencia, pero también de sus interpretaciones por los tribunales y de su contexto. Como expresión normalizada de hechos sociales (los riesgos del trabajo para la salud de quienes lo realizan), el “riesgo profesional” es un objeto en construcción, en un proceso más contradictorio que lineal.