Molecular-Based Magnetism in High-Spin Molecular Clusters and Three-Dimensional Networks Based on Cyanometalate Building Blocks

The field of molecule-based magnets is a relatively new branch of chemistry, which involves the design and study of molecular compounds that exhibit a spontaneous magnetic ordering below a critical temperature, Tc. One major goal involves the design of materials with tuneable Tc's for specific applications in memory storage devices. Molecule-based magnets with high magnetic ordering temperatures have recently been obtained from bimetallic and mixed-valence transition metal μ-cyanide complexes of the Prussian blue family. Since the μ-cyanide linkages permit an interaction between paramagnetic metal ions, cyanometalate building blocks have found useful applications in the field of molecule-based magnets. Our work involves the use of octacyanometalate building blocks for the self-assembly of two new classes of magnetic materials namely, high-spin molecular clusters which exhibit both ferromagnetic intra- and intercluster coupling, and specific extended network topologies which show long-range ferromagnetic ordering.

Interaction of the Trinuclear Triangular Secondary Building Unit [Cu 3 (μ 3 -OH)(μ-pz) 3 ] 2+ with 4,4′-Bipyridine. Structural Characterizations of New Coordination Polymers and Hexanuclear Cu II Clusters. 2°

By reacting 4,4′-bipyridine (bpy) with selected trinuclear triangular CuII complexes, [Cu3(μ3-OH)(μ-pz)3(RCOO)2(LL′)] [pz = pyrazolate anion; R = CH3, CH3CH2, CH2═CH, CH2═C(CH3); L, L′ = Hpz, H2O, MeOH] in MeOH, the substitution of monotopic ligands by ditopic bpy was observed. Depending on the stoichiometric reaction ratios, different compounds were isolated and structurally characterized. One- and two-dimensional coordination polymers (CPs), as well as two hexanuclear CuII clusters were identified. One of the hexanuclear clusters self-assembles into a supramolecular three-dimensional structure, and its crystal packing shows the presence of two intersecting channels, one of which is almost completely occupied by guest bpy, while in the second one guest water molecules are present. This compound also shows a reversible, thermally induced, single-crystal-to-single-crystal transition.

Wage Premia in Employment Clusters: Agglomeration Economies or Worker Heterogeneity?

The correlation between wage premia and concentrations of firm activity may arise due to agglomeration economies or workers sorting by unobserved productivity. A worker's residential location is used as a proxy for their unobservable productivity attributes in order to test whether estimated work location wage premia are robust to the inclusion of these controls. Further, in a locational equilibrium, identical workers must receive equivalent compensation so that after controlling for residential location (housing prices) and commutes workers must be paid the same wages and only wage premia arising from unobserved productivity differences should remain unexplained. The models in this paper are estimated using a sample of male workers residing in 33 large metropolitan areas drawn from the 5% Public Use Microdata Sample (PUMS) from the 2000 U.S. Decennial Census. We find that wages are higher when an individual works in a location that has more workers or a greater density of workers. These agglomeration effects are robust to the inclusion of residential location controls and disappear with the inclusion of commute time suggesting that the effects are not caused by unobserved differences in worker productivity. Extended model specifications suggest that wages increase with the education level of nearby workers and the concentration of workers in an individual's own industry or occupation.

Construcción de competencias colectivas regionales. La experiencia de conformación de Clusters y Sistemas Productivos Locales en Argentina

Fil: Belloni, Paula. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Consolidación de cadenas globales de valor y desarrollo de clusters locales : El caso de la maquinaria agrícola en Argentina

Fil: Langard, Federico. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.