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Resumen del trabajo presentado a la XXVIII International Conference on Coordination and Bioinorganic Chemistry, celebrada en Smolenice (Slovakia) del 5 al 10 de junio de 2022., From methanolic solutions of Ni(NO3)2, 5,5ˈ-dimethyl-2,2ˈ-bipyridine and LiTCNQ (TCNQ = 7,7,8,8-tetracyanidoquinodimethane), complex [Ni(5,5ˈ-dmbpy)3](TCNQ)2 was isolated and its thermal properties were studied. The complex is stable in air atmosphere up to 208 ºC. The thermal decomposition consists in 3 consecutive steps in the temperature ranges 208-274 ºC (weight loss of 10.0 %), 274-401 ºC (17.5 %) and 401-495 ºC (64.2 %). The weight of the solid residue (8.3 %) corresponds to formation of NiO (calc. 7.3 %).KTCNQ was prepared reacting boiling acetonitrile solutions of TCNQ and KI. It is thermally stable up to 300 ºC. Its crystal structure at 200 ºC was determined. KTCNQ consists of one crystallographically independent TCNQ- anion and one potassium cation K+. Each K+ cation is octa-coordinated by eight nitrogen atoms from cyanide groups of TCNQ- anions. This crystal structure corresponds to the high-temperature phase of KTCNQ. As expected, the cell volume is by 1.5 % larger than the reported value measured at 140 ºC., This work was supported by grants APVV-18-0016, VEGA 1/0189/22, VVGS-2020-1657, VVGS-PF-2021-1772 and Grant PGC2018–093451-B-I00 (Spain).

Trabajo presentado al 256th ACS National Meeting: "Nanoscience, Nanotechnology & Beyond", celebrado en Boston (US) del 19 al 23 de agosto de 2018.

Trabajo presentado en el American Chemical Society (ACS) National Meeting and Exposition (Division of Inorganic Chemistry), celebrado en Philadelphia, Pennsylvania, del 21 al 25 de agosto de 2016

Póster presentado a la 20th International Conference on Solid Compounds of Transition Elements, celebrada del 11 al 15 de abril de 2016 en Zaragoza (España)., A set of polytypoids (analogous to polytypes but with differences in chemical composition) provide a useful vehicle for studying the role of non-covalent interactions in establishing the packing arrangements in molecular solids. A group of 1D copolymers based on the same heterometallic {[Cubipy][Co(Orot)2bipy]}n backbone, seen in the Figure, presents both polar and centric modifications (H2Orot = orotic acid, C5H4N2O4; bipy = 2,2\'-bipyridyl, C10H8N2). In each link of the chain, Co and Cu are coordinated to one 2,2\'-bipyridyl ligand each, with the orotate groups acting as bridges. Each unit of the polymer contains hydrogen-bond donor and acceptor groups as well as aromatic groups that can participate in π…π interactions. Further coordination of copper by chloride yields a centric crystal structure in space group P(-1), while coordination by an aqua ligand at the same site yields a polar crystal with the acentric space group P1. Structural evidence points to the formation of non-covalent interactions as the driving force for the appearance of one structure or the other. The polar structure, moreover, undergoes a single crystal to single crystal transformation to produce a second polar structure with the same copolymer backbone. The structural features and non-covalent forces are compared and discussed.

Resumen del trabajo presentado a la Conference of the Czech and Slovak Crystallographic Association, celebrada en Tábor (República Checa) del 12 al 15 de septiembre de 2016., Schiff bases are often used as ligands for the coordination of cobalt due to their multi-donor properties and consequent versatility. In our quest for Co(II) complexes as magnetically active materials we have isolated two polymorphs of [Co2(o-van-en)3]×4CH3CN (1 and 2) based on the Schiff base ligand o-van-en synthesized by the reaction of ethylenediamine with o-vanillin in 1:2 molar ratio. The triclinic (P-1) polymorph 1 was obtained after room temperature crystallization of the acetonitrile solution of the reaction product of the Schiff base with cobalt hydroxide in air. Differences in reaction and crystallization conditions produced the monoclinic form 2 (space group P21/c). Both polymorphs were chemically and spectroscopically characterized, and the results indicated spontaneous oxidation of Co(II) to Co(III). The crystal structures of both 1 and 2 are built up of molecules of the centrosymmetric dinuclear complex [Co2(o-van-en)3], in which each Co(III) atom is coordinated by one tetradentate o-van-en ligand in an uncommon bent fashion. The pseudooctahedral coordination of the Co(III) atom is completed by one phenolato O and one amidic N atom of the same arm of the bridging o-van-en ligand. In addition, the asymmetric units of both polymorphs contain two acetonitrile solvate molecules. In polymorph 2, consistent with the symmetry of the space group, the dinuclear {Co2} units are arranged in an alternating ABABAB fashion, in contrast to the AAA arrangement of the dinuclear units in polymorph 1. As a consequence, both polymorphs differ in the positions of the acetonitrile solvate molecules and in the pattern of intermolecular interactions. Differences of some geometrical parameters, e.g., torsion angles were observed, too., This work was supported by P. J. Šafárik University in Košice (VVGS-PF-2016-72623, VVGS-2016-265). The stay of AV in University of Zaragoza was supported by National Scholarship Programme of the Slovak Republic.

Resumen del póster presentado al American Crystallographic Association Annual Meeting, celebrado en Philadelphia (US) del 25 al 29 de julio de 2015., The citratobis(aqua)gadolinium compound with empírical formula [Gd(Hcitr)(H20)2] [Hcitr = citrate (3-, C6H5O7(3-)] has been reportad previously as a 1D polymer which in the solid is a stoichiometric monohydrate, [Gd(Hcitr)(H20)2]n·nH20, prepared hydrothermally at a temperatura of 100 ºC (10 days). (For present naming purposes the aqua ligand is treated as distinct from the unligated water, which we call water of hydration.) We describe here the preparation, by wet chemistry means, of the stoichiometric dihydrate, [Gd(Hcitr)(H20)2]n·2nH20, whose basic building block in the crystal is a two-dimensional polymer of the complex. The anhydrous form, also a two-dimensional polymer, is preparad from the dihydrate at 77 'C (several hours) in a single-crystal to single-crystal transformation. This transformation, in the course of which no evidence of a monohydrate is observad, is fully reversible, with the same single-crystal sample having been used for the characterization of the initial dihydrate, the form with no free water, and the restored dihydrate. The evolution of the SCSC transformation can be followed neatly by means of axial photographs. The initial citratobis(aqua)complex dihydrate and the dehydrated citratobis(aqua) complex possess the same two-dimensional layer structure, but with significant layer slippage occurring between the two forms.

Resumen del trabajo presentado a la "VII Reunión de la Sociedad Española de Técnicas Neutrónicas" celebrada en Pamplona del22 al 25 de junio de 2014., El movimiento de protones en el interior de espacios reducidos es un tema de gran interés en numerosas áreas de investigación. A pesar de que la mayoría de materiales empleados para el transporte y almacenaje de moléculas e iones suelen ser materiales porosos, se ha logrado obtener sustancias sintéticas no porosas capaces de ceder y capturar pequeñas moléculas, entre las cuales se encuentra el agua. Por otro lado, el transporte de protones implica la ruptura y formación de enlaces dentro del sólido, convirtiéndolo en algo más que un simple espectador. Este proceso, conocido como alambre de protones, se explica en base al mecanismo de Grotthuss. A pasar de su simplicidad conceptual, la mayoria de resultados se basan o necesitan el apoyo de cálculos teóricos. En este trabajo se presenta un polímero 1-D basado en manganeso y citrato. El ploímero esta formado por unidades [Mn4(citrato)4] propagadas a traves de unidades [Mn4(H2O)6]2+. La carga negativa de la cadena polimérica está compensada con unidades [Mn(H2O)5]2+ que cuelgan de ella y [Mn4(H2oO)6]2+ que se localizan entre las cadenas poliméricas. Asi pues el complejo consta, por monómero, de 21 moléculas de agua coordinadas y 9 libres alojadas entre las cadenas poliméricas. Este compuesto experimenta una pérdida de 3 moleculas de agua cuando se deja al aire a pesar de no presentar canales o poros en su estnructura. Cuando el cristal se expone a una atmósfera húmeda, estas tres moléculas de agua son reabsorbidas regenerando completamente la estructura inicial. Sin embargo, al llevar a cabo la rehidratación bajo atmósfera de D2O se ha observado un intercambio total de todos los H de las moléculas de agua (coordinadas y libres) por deuterio. Las estructuras antes y después del intercambio fueron caracterizadas por difracción de neutrones. Esto se explica gracias a la observación de cadenas de moléculas de agua unidas por puentes de hidrógeno que atraviesan la estructura completa. El desorden observado en los átomos de hidrógeno permite su desdoblamiento en dos componentes que encajan con los dos pasos fundamentales del mecanismo de Grotthuss., Financiación económica conseguida a través de: Ministerio de Ciencia e Innovación (Proyectas MAT2011-27233-COZ-01 y MAT2011-27233-C02-02); Fondo Europeo de Desarrollo Regional (FEDER); CONSOLIDER-INGENIO en Nanociencia Molecular (CSD 2007-00010). EFV agradece al Ministerio de Educación la beca pre-doctoral bajo el programa "Becas y Contratos FP" (referencia AP2009-4211); Diputación General de Aragón: Servicio General de Apoyo a la Investigación - SAI de la Universidad de Zaragoza.

The reaction of NiCl2, K2C2O4 H2O and 2,2'-bipyridine (bpy) in water-ethanol solution at 281K yields light-purple needles of the new pentahydrate of bis(2,2'-bipyridine) oxalatonickel(II), [Ni(C2O4)(C10H 8N2)2] 5H2O or [Ni(ox)(bpy)2] 5H2O, while at room temperature, deep-pink prisms of the previously reported tetrahydrate [Ni(ox)(bpy)2] 4H2O [Román, Luque, Guzmán-Miralles & Beitia (1995), Polyhedron, 14, 2863-2869] were gathered. The asymmetric unit in the crystal structure of the new pentahydrate incorporates the discrete molecular complex [Ni(ox)(bpy)2] and five solvent water molecules. Within the complex molecule, all three ligands are bonded as chelates. The complex molecules are involved in an extended system of hydrogen bonds with the solvent water molecules. Additionally, π-π interactions also contribute to the stabilization of the extended structure. The dehydration of the pentahydrate starts at 323K and proceeds in at least two steps as determined by thermal analysis. © 2014 International Union of Crystallography., This work was supported by the Slovak grant agencies VEGA (grant No. 1/0075/13) and APVV (grant No. APVV-0132–11). Funding from the Ministry of Science and Innovation (Spain) under grant No. MAT2011-27233-C02-1, from the Diputación General de Aragón and from the European Union Regional Development Fund is gratefully acknowledged. NF thanks the National Scholarship Programme of the Slovak Republic for financial support of her research stay at the University of Zaragoza (Spain).

Resumen del trabajo presentado a la: "14th International Conference on Molecule-Based Magnets" celebrada en San Petersburgo (Rusia) del 5 al 9 de julio de 2014., The discovery of Single Molecule Magnets (SMMs) has represented a revolution in the field of molecular magnetism. Many research groups have focused their efforts on the development of new SMMs. For applications, including putative technological applications, however, the further step of arranging those compounds into well-ordered structures still is a pending issue. Coordination chemistry is proving to be a powerful tool for the preparation of polymeric nets of SMMs. As described in a recent review by Clerac, there are very few examples of SMMs arranged in networks. As we propose in this presentation, the number and functional possibilities of SMM networks can readily be increased in the case of citrate cubanes. The transition-metal citrate cubane [M4citrate4]8- is a symmetrical, anionic molecular fragment that possesses twelve partially negatively charged oxygen atoms (and twelve coordinated but reactive oxygen centers) around its periphery. The cobalt variants have proved to be SMMs, as demonstrated by Murrie et al. and by others. Interestingly, all of the negatively charged points on the fragment surface are potential linkage positions for metal atoms whose adhesion can give extended networks with dimensionalities ranging from zero- to three. In this presentation we apply this viewpoint to the previously reported [M4citrate4]8- cubanes with transition metal centres and to new ones, giving compounds with more than 10 different combinations of linkage points. Some of these products present an unexpected variety of magnetic and dynamic phase behaviour, including chemical reactions, phase transitions and proton transport. All of these products have different patterns of peripheral metal-atom linkage to the 12 surface-resident and 12 encrusted oxygen atoms of the cubane fragment. These results show that transition metal citrate cubanes are excellent synthons for the preparation of a potentially boundless family of networks of ordered SMMs with a high probability of finding new magnetic and dynamic properties. A systematic naming scheme for the citrate cubane topology is used to provide simple descriptions of the diverse linkage geometries found to date., Funding was provided by the Ministerio de Ciencia e Innovación (Spain) (Grants MAT2007- 61621, MAT2008-04350, MAT2009-13977-C03, MAT2011-27233-C02-01 and MAT2011-27233-C02-02). European Union Regional Development Fund (FEDER) (program CONSOLIDER-INGENIO in Molecular Nanoscience (reference CSD 2007-00010)). EFV thanks the Ministry of Education (Spain) for a pre-doctoral scholarship under the program ‘Becas y Contratos FPU’ (reference AP2009-4211). Funding was also provided by the Diputación General de Aragón (Spain).

Resumen del póster presentado a la 19th International Conference on Magnetism celebrada en Korea del 8 al 13 de julio de 2012., The modulation of the magnetic properties of SMMs and their organization in extended magnetic arrays are, at the present, some of the top areas in the field of molecular magnetism for the implication in the improvement of the physical properties of the SMM and the potential use in devices such as for data storage. Few polymers of SMM have been structurally characterized in spite of the number of known SMM. [Co4citrate4]8- cubanes can behave as SMM. We have reported recently the union of these cubanes through “Co(H2O)2ETG” (ETG=ethylene glycol) bridges and the formation of anionic 2D layers. These layers crystallize in the tetragonal system, P-421c space group, with counterions (Cs+ or Rb+), water and ETG molecules connecting the layers though electrostatic interactions and hydrogen bridges. The magnetic studies show the co-existence of two magnetic nets: the SMM net and the one formed by the bridged cobalt atoms and also shows the influence of the counterions in the layer magnetic properties. Two intriguing relaxation processes with different characteristics timescales are observed. Moreover, [Co4citrate4]8- cubanes can also organize in 3D, diamond-like structural arrays showing SMM magnetic behaviour below 6K with an enegry barrier of 54K and magnetic ordering below 2.7K.