Nanotecnología: máquinas moleculares o cómo hacer que algo se mueva cuando tú quieres

La nanotecnología ha irrumpido en los centros de investigación de una manera impresionante en los últimos años. Parece útil y necesario el tener una noción sobre qué es y qué puede esperarse en un futuro de esta nueva rama de la tecnología. Para ello se ha utilizado, a modo de guía, uno de los campos dentro de la nanotecnología: la síntesis de máquinas moleculare

Multivalent Molecular Shuttles – Effect of Increasing the Number of Centers in Switchable Catalysts

Producción CientíficaA family of three molecular shuttles based upon ammonium/triazolinium salt motifs with one, two, and three catalytic centers were prepared along with their corresponding non‐interlocked threads. The switching process for all rotaxanes was tested through an in situ procedure in solution. Furthermore, their organocatalysis of two Michale‐type reactions by iminium activation was tested to check whether the increase of the number of catalytic centers in the same shuttle is a decisive factor to improve their efficiencies compared with those of single‐active‐site organocatalytic shuttles under the same conditions.Ministerio de Economía, Industria y Competitividad (Project CTQ 2013-41067-P

Synergistic Effect of Tetraaryl Porphyrins Containing Corannulene and Other Polycyclic Aromatic Fragments as Hosts for Fullerenes. Impact of C60 in a Statistically Distributed Mixture of Atropisomers

Producción CientíficaSymmetric meso-tetraarylporphyrins bearing phenanthrene, pyrene, and corannulene moieties in meta positions have been synthesized in a straightforward procedure under microwave irradiation by quadruple Suzuki–Miyaura reactions. Their 1H NMR spectra showed the typical pattern of four atropisomers distributed according to their statistical ratio not properly separable due to their fast isomerization. Their ability to bind buckminsterfullerene has been tested with the whole mixture, and different behaviors have been found, α4 isomer corannulene-substituted porphyrins being the best hosts in the family.Ministerio de Economía, Industria y Competitividad (Project CTQ 2013-41067-P

Dual-Tweezer Behavior of an Octapodal Pyrene Porphyrin-Based System as a Host for Fullerenes

Producción CientíficaThe incorporation of eight pyrene units in a single porphyrin core exhibits a great synergistic effect, resulting in high affinity toward C60 and C70. This octapyrene porphyrin is easily accessible by a straightforward two-step synthetic approach that involves an octuple Suzuki reaction. The new supramolecular platform can present single- or double-tweezer fullerene hosting behavior. The switch from double- to single-tweezer behavior is triggered by the simple coordination of Zn2+ to the porphyrin. Both the octapyrene porphyrin 2HPOP and its zinc metalloporphyrin analogue ZnPOP show very high affinity for C60 and C70, while simultaneously allowing the discrimination of C70 over C60 in a C60/C70 mixture. The use of 2HPOP and ZnPOP for the enrichment of real fullerene mixtures is also demonstrated.Ministerio de Economía, Industria y Competitividad (grants CTQ 2013-41067-P / PGC 2018-099470-B-100

From Induced-Fit Assemblies to Ternary Inclusion Complexes with Fullerenes in Corannulene-Based Molecular Tweezers

Producción CientíficaThe participation of the tether moiety in fullerene recognition of corannulene-based molecular tweezers is known to be an important factor. In the present work, we describe the synthesis of a set of fullerene receptors bearing two corannulene units located at a suitable distance to effectively interact with C60 and C70. The tether comprises a fluorene-like scaffold where an assortment of different groups with variable electronic properties has been grafted. The photophysical and electrochemical properties of all final compounds have been unveiled and correlated to the donor/acceptor (DA) nature of the tether. Despite these strong variations, their affinity toward fullerenes cannot be correlated in any way to simple DA behavior as the main contribution to the interaction correspond to London dispersion forces. We found, however, that the sulfur-derived subfamily is able to adapt better to the fullerene outer surface slightly increasing the charge transfer and electrostatic attractive interactions being the most outstanding example the case of thiophene 4-S with C70 as it is capable of forming a ternary 2:1 inclusion complex in solution with an electronic binding energy that offsets entropy and desolvation penalties typically associated with higher-order inclusion complexes.Ministerio de Ciencia, Innovación y Universidades (project (projects numbers PGC2018-096880-A-I00, MCIU/AEI/FEDER, UE, PGC2018-099470-B-I00, and MCIU/AEI/FEDER, UE

Affinity modulation of photoresponsive hosts for fullerenes: light-gated corannulene tweezers

Producción CientíficaSix azobenzene derivatives bearing polyaromatic fragments have been prepared and their reversible photoisomerization has been assessed. Corannulene-functionalized molecules have demonstrated excellent switchable hosting abilities towards fullerenes in which an interesting range of affinities has been found. The success of this design relies upon the reversible formation and destruction of tweezer-like structures.Ministerio de Economía, Industria y Competitividad (Project CTQ 2013-41067-P

Copper Complexes in the Promotion of Aldol Addition to Pyridine-2-carboxaldehyde: Synthesis of Homo- and Heteroleptic Complexes and Stereoselective Double Aldol Addition

Producción CientíficaCuCl2·2H2O and Cu(ClO4)2·6H2O are able to promote aldol addition of pyridine-2-carboxaldehyde (pyca) with acetone, acetophenone, or cyclohexenone under neutral and mild conditions. The general and simple one-pot procedure for the aldol addition to Cu(II) complexes accesses novel Cu complexes with a large variety of different structural motifs, from which the aldol-addition ligand can be liberated by treatment with NH3. Neutral heteroleptic complexes in which the ligand acts as bidentate, or homoleptic cationic complexes in which the ligand acts as tridentate can be obtained depending on the copper salt used. The key step in these reactions is the coordination of pyca to copper, which increases the electrophilic character of the aldehyde, with Cu(ClO4)2 leading to a higher degree of activation than CuCl2, as predicted by DFT calculations. A regio- and stereoselective double aldol addition of pyca in the reaction of Cu(ClO4)2·6H2O with acetone leads to the formation of a dimer copper complex in which the novel double aldol addition product acts as a pentadentate ligand. A possible mechanism is discussed. The work is supported by extensive crystallographic studies.2019-12-312019-12-31Ministerio de Economía, Industria y Competitividad (Project CTQ 2013-41067-P

Estudio de máquinas moleculares y derivados poliaromáticos con capacidad de establecer interacciones supramoleculares

La presente tesis trata sobre dos aspectos fundamentales dentro del campo de la química supramolecular. Por un lado, se han preparado dos familias de interruptores moleculares basados en rotaxanos que han sido completamente caracterizados y sus propiedades han sido evaluadas por diversas técnicas experimentales. Se ha hecho especial hincapié en su uso como organocatalizadores conmutables concluyendo que estos compuestos ejercen un control cinético excelente en diversas reacciones de adición tipo Michael. Por otro lado, se han sintetizado dos series de compuestos que poseen hidrocarburos policíclicos aromáticos planos y no planos con capacidad de formar aductos con fullerenos a través de fuerzas de dispersión. Los resultados demostraron que se obtuvieron unos derivados muy interesantes, uno fotosensible capaz de modificar su afinidad por fullerenos, y otro en cuya cooperación entre un fotosensibilizador y hasta cuatro unidades del fragmento poliaromático produjeron una muy eficiente formación del complejo de inclusión.Departamento de Química Física y Química InorgánicaDoctorado en Química: Química de Síntesis, Catálisis y Materiales Avanzado

Self-resetting bistable redox molecular machines for fullerene recognition

Producción CientíficaAddressing control over molecular machines resulting in variable output modulation by mimicking nature mechanisms is a current hot topic. The exploitation of reversibility in thiol/disulfide motifs in chemical systems flanked by nonplanar corannulene moieties capable to recognize fullerenes is presented herein. Two redox-based machines have been conceived for this purpose: an ON/OFF switch that activates its binding properties upon dimerization and a self-resetting (i.e., with an automated backward process) host that substantially modulates its affinity.Ministerio de Ciencia, Innovación y Universidades - Agencia Estatal de Investigación - Fondo Europeo de Desarrollo Regional (projects PGC2018-096880-A-I00 and PGC2018-099470–B-I00)Junta de Castilla y León (predoctoral contract Orden EDU/574/2018