Supramolecular coordination chemistry of aromatic polyoxalamide ligands: A metallosupramolecular approach toward functional magnetic materials

The impressive potential of the metallosupramolecular approach in designing new functional magnetic materials constitutes a great scientific challenge for the chemical research community that requires an interdisciplinary collaboration. New fundamental concepts and future applications in nanoscience and nanotechnology will emerge from the study of magnetism as a supramolecular function in metallosupramolecular chemistry. Our recent work on the rich supramolecular coordination chemistry of a novel family of aromatic polyoxalamide (APOXA) ligands with first-row transition metal ions has allowed us to move one step further in the rational design of metallosupramolecular assemblies of increasing structural and magnetic complexity. Thus, we have taken advantage of the new developments of metallosupramolecular chemistry and, in particular, the molecular-programmed self-assembly methods that exploit the coordination preferences of paramagnetic metal ions and suitable designed polytopic ligands. The resulting self-assembled di- and trinuclear metallacyclic complexes with APOXA ligands, either metallacyclophanes or metallacryptands, are indeed ideal model systems for the study of the electron exchange mechanism between paramagnetic metal centers through extended π-conjugated aromatic bridges. So, the influence of different factors such as the topology and conformation of the bridging ligand or the electronic configuration and magnetic anisotropy of the metal ion have been investigated in a systematic way. These oligonuclear metallacyclic complexes can be important in the development of a new class of molecular magnetic devices, such as molecular magnetic wires (MMWs) and switches (MMSs), which are major goals in the field of molecular electronics and spintronics. On the other hand, because of their metal binding capacity through the outer carbonyl-oxygen atoms of the oxamato groups, they can further be used as ligands, referred to as metal–organic ligands (MOLs), toward either coordinatively unsaturated metal complexes or fully solvated metal ions. This well-known “complex-as-ligand” approach affords a wide variety of high-nuclearity metal–organic clusters (MOCs) and high-dimensionality metal–organic polymers (MOPs). The judicious choice of the oligonuclear MOL, ranging from mono- to di- and trinuclear species, has allowed us to control the overall structure and magnetic properties of the final oxamato-bridged multidimensional (nD, n = 0–3) MOCs and MOPs. The intercrossing between short- (nanoscopic) and long-range (macroscopic) magnetic behavior has been investigated in this unique family of oxamato-bridged metallosupramolecular magnetic materials expanding the examples of low-dimensional, single-molecule (SMMs) and single-chain (SCMs) magnets and high-dimensional, open-framework magnets (OFMs), which are brand-new targets in the field of molecular magnetism and materials science

La neumonía adquirida en la comunidad de los ancianos: diferencias entre los que viven en residencias y en domicilios particulares

Objetivo: La neumonía adquirida en la comunidad (NAC) de los ancianos que viven en una residencia se considera distinta del resto en cuanto a etiología, forma de presentación y pronóstico. Sin embargo, existen pocos estudios en nuestro país que confirmen estos aspectos, sin olvidar las diferencias etiológicas regionales de las NAC. Pacientes y métodos: Se ha realizado un estudio prospectivo de 18 meses de duración (2002-2003), en el que se ha incluido a todos los pacientes mayores de 65 años que ingresaron por NAC en nuestro hospital. Se recogieron las características clínicas, analíticas y radiológicas haciendo especial hincapié en la situación funcional --­escala del Eastern Cooperative Oncology Group (ECOG), índices de Barthel y Karnofsky--­ y en la comorbilidad. Para el diagnóstico etiológico se realizaron 2 hemocultivos, antígeno de Legionella en orina y serología de gérmenes atípicos; en los casos indicados también se practicó cultivo bacteriológico de muestras respiratorias. Resultados: Se incluyó a 91 pacientes, de ellos 25 procedían de residencias. Estos últimos tenían mayor edad (82 ± 4 frente a 73 ± 5 años; p = 0,0001), mayor comorbilidad global (p = 0,0001) --como enfermedades aisladas eran significativamente más comunes la diabetes mellitus, la enfermedad cerebrovascular, la insuficiencia cardíaca congestiva crónica y la demencia-- y peor estado funcional (ECOG: 2,09 ± 0,9 frente a 0,93 ± 1,1, p = 0,001; índice de Barthel: 19 ± 33 frente a 77 ± 35, p = 0,001; índice de Karnofsky: 51 ± 17 frente a 78 ± 23, p = 0,001). En cuanto a las características clínicas, encontramos diferencias significativas en la frecuencia respiratoria (39 ± 11 frente a 27 ± 7 respiraciones/min; p = 0,001), la presión arterial diastólica (69,5 ± 20 frente a 79,2 ± 18 mmHg; p = 0,029) y en la temperatura (36,6 ± 1,2 frente a 37,7 ± 1,1 °C; p = 0,001). En la radiografía de tórax, la NAC de residencia presentó mayor número de lóbulos afectados (p = 0,004). Además, estos pacientes tenían mayor hipoxemia, acidosis, anemia, hipoalbuminemia y elevación de las cifras de urea y creatinina. Asimismo, la puntuación en la escala de Fine fue superior (134 ± 26 frente a 95 ± 28; p = 0,001) y presentaron mayor mortalidad (7/25 frente a 3/66; p = 0,005). En la mayoría de los pacientes no se pudo encontrar un diagnóstico etiológico, pero no se observaron diferencias significativas entre ambos grupos. La variable predictora de mortalidad de los ancianos de la serie --modelo de regresión (pasos sucesivos)-- fue la urea (R2 corregida = 0,452). Conclusiones: En nuestra población, los ancianos que viven en residencias tienen mayor edad, pluripatología e importante deterioro funcional. En estas circunstancias la NAC adquiere especial gravedad y es una causa importante de mortalidad, pese a que los agentes etiológicos no parecen diferir de los habituales

Long-Range Magnetic Coupling through Extended p-Conjugated Aromatic Bridges in Dinuclear Copper(II) Metallacyclophanes

[EN] Self-assembly of 1,4-phenylenebis(oxamate) and 4,4`-biphenylenebis(oxamate) ligands and Cu2+ ions gives two new dinuclear copper(II) metallacyclophanes where the two metal centers are connected by double para-substituted aromatic diamide bridges. Despite the relatively large intramolecular Cu¿Cu distance of ca. 8 and 12 Å for each complex, magnetic susceptibility measurements evidence strong to moderately strong intramolecular antiferromagnetic couplings (¿J values of the order of 100 and 10 cm-1, respectively). Density functional theory calculations on these compounds and their homologues with linear oligo-p-phenylenediamide bridges predict a rather slow exponential decay of magnetic coupling with increasing intermetal distance (r values up to 25 Å) along this novel series of dicopper metalla-amidocyclophanes.This work was supported by the Ministerio de Ciencia y Tecnología (Spain) through the Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica (Projects BQU2001-2928 and BQU2001-3017) and the Ramón y Cajal program. Further support from the TMR program of the European Union (Contract ERBFM-RXCT980181) is acknowledged. E.P. thanks the Ministerio de Educación, Cultura y Deporte (Spain) for a grant.Pardo, E.; Faus, J.; Julve, M.; Lloret, F.; Muñoz Roca, MDC.; Cano, J.; Ottenwaelder, X.... (2003). Long-Range Magnetic Coupling through Extended p-Conjugated Aromatic Bridges in Dinuclear Copper(II) Metallacyclophanes. Journal of the American Chemical Society. 125(36):10770-10771. https://doi.org/10.1021/ja030060fS10770107711253

Slow Magnetic Relaxation in a Hydrogen-Bonded 2D Array of Mononuclear Dysprosium(III) Oxamates

The reaction of <i>N</i>-(2,6-dimethylphenyl)­oxamic acid with dysprosium­(III) ions in a controlled basic media afforded the first example of a mononuclear lanthanide oxamate complex exhibiting a field-induced slow magnetic relaxation behavior typical of single-ion magnets (SIMs). The hydrogen-bond-mediated self-assembly of this new bifunctional dysprosium­(III) SIM in the solid state provides a unique example of 2D hydrogen-bonded polymer with a herringbone net topology

Slow Magnetic Relaxation in a Hydrogen-Bonded 2D Array of Mononuclear Dysprosium(III) Oxamates

The reaction of <i>N</i>-(2,6-dimethylphenyl)­oxamic acid with dysprosium­(III) ions in a controlled basic media afforded the first example of a mononuclear lanthanide oxamate complex exhibiting a field-induced slow magnetic relaxation behavior typical of single-ion magnets (SIMs). The hydrogen-bond-mediated self-assembly of this new bifunctional dysprosium­(III) SIM in the solid state provides a unique example of 2D hydrogen-bonded polymer with a herringbone net topology

Rational design of a new class of heterobimetallic molecule-based magnets: Synthesis, crystal structures, and magnetic properties of oxamato-bridged M 3M2 (M = LiI and MnII; M = NiII and CoII) open-frameworks with a three-dimensional honeycomb architecture

[EN] Two new series of oxamato-bridged heterobimetallic coordination networks of general formula Li-5[Li3M2(mpba)(3)(H2O)(6)] center dot 31H(2)O [M= Ni-II (1a) and Co-II (1b)] and Li-2[Mn3M2(mpba)(3)(H2O)(6)] center dot 22H(2)O [M = Ni-II (2a) and Co-II (2b)] have been prepared from the metal- mediated self-assembly of the hexakis(bidentate), triple-stranded dinickel(I) and dicobalt(II) complexes [M-2(mpba)(3)](8) [mpba = meta-phenylenebis(oxamato)] with either monovalent lithium(I) or divalent manganese(II) ions respectively, in water. X-ray structural analyses of 1a and 1b show an anionic three-dimensional network formed by an infinite parallel array of oxamato-bridged (Li3M2II)-M-I (M = Ni and Co) hexagonal layers, which are interconnected through three m-phenylenediamidate bridges between the M-II ions of opposite propeller chirality (Lambda and Lambda) to give dinuclear metallacrypt and cores of the meso-helicate-type. The intralayer Li-M distance through the oxamate bridge is 5.380(3) (1a) and 5.396(5) (1b) angstrom, while the interlayer M-M distance through the triple m-phenylenediamidate bridge is 6.856(3) (1a) and 6.851(3) (1b) angstrom. Overall, this leads to an open-framework honeycomb structure with large hexagonal pores of ca. 21.8 (1a) and 21.5 angstrom (1b) in diameter which are occupied by linear arrays of water-bridged Li-I countercations. Variable-temperature (2.0-300 K) dc magnetic susceptibility and variable-field (0-5.0 T) magnetization measurements on these two series of compounds reveal a distinct magnetic behavior mainly depending on the diamagnetic or paramagnetic nature of the Li-I and Mn-II ions, respectively. Compounds 1a and 1b behave as rather well-isolated MI2II (M = Ni and Co) dimers with a moderate to weak ferromagnetic coupling(J(Ni-Ni) = + 3.17 cm (1) and J(Co-Co) = + 1.03 cm (1)) between the two M-II ions across the triple m-phenylenediamidate bridge, together with either an appreciable to remarkable local ion axial magnetic anisotropy (D-Ni = -3.35 cm (1)) or spin-orbit coupling (lambda(Co) = - 167.3 cm (1)); the next nearest-neighbor magnetic interactions between the M-II ions through the diamagnetic Li-I ions are negligible. Compounds 2a and 2b behave instead as strongly coupled oxamato-bridged (Mn3M2II)-M-II (M = Ni and Co) ferrimagnetic planes which are weakly interacting through the m-phenylenediamidate bridges, leading thus to a long-range 3D ferromagnetic order at T-C = 6.5 K. In addition, the variable-temperature (2.0-12 K) ac magnetic susceptibility measurements on 2a and 2b show an intriguing frequency-dependent magnetic behavior characteristic of a spin-glass dynamics. This glassy behavior is likely attributed to their amorphous character and/or the moderate to strong magnetic anisotropy of the dinickel(II) and dicobalt(II) precursors.This work was supported by the Ministerio de Educación y Ciencia (MEC, Spain) (Projects CTQ2007-61690 and CSD2007-00010), the Ministère de l Enseignement Supérieur et de la Recherche (MESR, France), the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Brazil) (Project COFECUB 460/04), and the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG, Brazil) (Projects CEX1837/06 and PRONEX 526/07). D.C., E.P., and M.-C.D. thank the CAPES, the MEC, and the MESR/UPMC for grants. J.C. acknowledges the Universitat de València for an invited researcher grant.Cangussu, D.; Pardo, E.; Dul, MC.; Lescouëzec, R.; Herson, P.; Journaux, Y.; Pedroso, EF.... (2008). Rational design of a new class of heterobimetallic molecule-based magnets: Synthesis, crystal structures, and magnetic properties of oxamato-bridged M 3M2 (M = LiI and MnII; M = NiII and CoII) open-frameworks with a three-dimensional honeycomb architecture. Inorganica Chimica Acta. 361(12-13):3394-3402. https://doi.org/10.1016/j.ica.2008.02.042S3394340236112-1