Materials Moleculars Nanoporosos Magnètics (2004)

Aquesta Tesi Doctoral sha basat en el disseny de materials moleculars nanoporosos i magnetics. En aquest sentit, sha dissenyat una nova estrategia sintetica enfocada a lobtencio de materials hibrids metallorganics que combinin canals de grans dimensions i propietats magnetiques interessants. Fins aleshores, el disseny dun material daquestes caracteristiques presentava certes contradiccions sintetiques, fet que provocava que la seva sintesi resultes molt complicada. No obstant, la introduccio, per part del nostre grup, duna variacio consistent en lus de lligands amb caracter paramagnetic ha permes obtenir diversos materials amb ambdues caracteristiques.
Un primer material molecular nanoporos i amb ordenament magnetic (designat com a MOROF-1, metal-organic radical open-framework) sha sintetitzat utilitzant un io metallic com el coure(II) i un radical perclorotrifenilmetilic trifuncionalitzat amb tres grups carboxilics (D. MASPOCH, NATURE MATERIALS, 2002, 2, 190). Aquest compost presenta unes caracteristiques nanoporoses realment interessants. Les dimensions dels seus canals son daproximadament 3 nm. A mes, la desorpcio i absorcio de molecules de dissolvent (etanol o metanol) provoca uns canvis estructurals sorprenents: el materials te un comportament semblant al duna esponja molecular; conferint-li unes bones caracteristiques per poder actuar com a sensor de dissolvents com el metanol i etanol. A mes, aquesta estructura altament porosa sordena ferromagneticament a baixes temperatures.
Aquest material tambe ha vingut acompanyat de dos nous materials, tots ells amb interessants propietats poroses i magnetiques. El material MOROF-2 (D. MASPOCH ET AL., CHEM COMMUN., 2004, 1164) es defineix com un solid paramagnetic amb una topologia arquitectonica inedita fins ara i amb uns canals helicoidals. Altrament, el material MOROF-3 novament sordena magneticament i tambe presenta una porositat important.
Per altra banda, lus daquest radicals com a blocs moleculars paramagnetics enllacats per ponts dhidrogen tambe ha permes lobtencio dels primers materials moleculars purament organics porosos i magnetics, els quals son estables en absencia de dissolvent pressenten una estabilitat termica elevada (275o(c)). Aici, lempaquetament del radical PTMDC forma un material molecular paramagnetic (POROF-1) amb una estructura composta duns nanocontenidors moleculars hidrofobics de fins a 1 nm de diametre connectats a traves de finestres hidrofiliques de 5 A (D. MASPOCH ET AL., J. AM. CHEM. SOC., 2004, 126, 730) . Daltra banda, el radical PTMTC forma un segon material purament organic poros (POROF-2), el qual sordena magneticament (D. MASPOCH, ANGEW. CHEM. INT. ED., 2004, 43, 1828).
Sha demostrat doncs la viabilitat de lus daquests nous materials moleculars porosos i magnetics com a materials de partida per la formacio de materials moleculars multifuncionals. Aplicant aquesta aproximacio, sha aconseguit sintetitzar un materials molecular poros que combina canals formats per parets amb diversos grups quirals i propietats magnetiques dinteres.
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This thesis has mainly focused on the design of nanoporous and magnetic molecular materials. In this way, in our group, we have designed a new synthetic strategy for the obtaining of hybrid metal-organic materials that could combine large nanopores and interesting magnetic properties. Up to now, the design of this kind of materials shows some synthetic contradictions. However, the recently introduction of paramagnetic ligands in our group has allowed the obtaining several materials that show both characteristics.
A first nanoporous molecular ferromagnet (referred as MOROF-1, Metal-Organic Radical Open-Framework) has been synthesized by the use of a paramagnetic metal ion such as Cu(II) and a perclorotrifenilmethyl radical trifucntionalized with three carboxylic functions (D. MASPOCH, NATURE MATERIALS, 2002, 2, 190). This material shows a really interesting nanoporous characteristics. The dimensions of their channels are around 3 nm. Furthermore, the desorption and absorption of solvent molecules (ethanol or methanol) produces surprising structural changes: this material shows a similar behavior of that a molecular sponge; giving an excellent characteristics to behave as a sensor for solvents such as ethanol or methanol. Furthermore, this highly porous structure shows a magnetic ordering at low temperatures.
This material has been accompanied by two new materials, both with interesting porosity and magnetic properties. MOROF-2 (D. MASPOCH ET AL., CHEM COMMUN., 2004, 1164) is a paramagnetic solid with a new topology and helicoidal channels. Moreover, MOROF-3 also shows a magnetic ordering and a highly porosity characteristic.
On the other hand, the use of this radicals as paramagnetic organic building-blocks linked by hydrogen-bonds has allowed the design of the first purely organic nanoporous and magnetic materials, which are stable in absence of solvent molecules and are stable at high temperatures (275 oC). Thus, the proper packing of PTMDC radical forms a paramagnetic molecular material (POROF-1) with a structure composed by hydrophobic nanocontainers of 1 nm connected by narrow hydrophilic windows of 5 A (D. MASPOCH ET AL., J. AM. CHEM. SOC., 2004, 126, 730). Furthermore, PTMTC radical forms a second purely organic material (POROF-2), which are magnetically ordered (D. MASPOCH, ANGEW. CHEM. INT. ED., 2004, 43, 1828).
It has been also showed the possible use of this new nanoporous and magnetic molecular materials for the formation of new multifunctional molecular materials. With this aim, a new porous materials that combines channels covered by chiral groups and interesting magnetic properties has been obtained.