Asymmetry and magnetism in bis(oximato)-bridged heterobimetallic compounds: a computational approach

A density functional study of exchange coupling was carried out for a series of heterobinuclear oximato-bridged transition metal complexes. Model calculations were used to examine the influence of the electronic configuration of the metal atoms on the coupling constants. This analysis was complemented by a study of the variation of the coupling constant with the most usual structural distortions within this family of compounds. The influence of the nature of the terminal ligands as well as that of the symmetry on the bridge were also investigated.     

About the calculation of exchange coupling constants in polynuclear transition metal complexes

The application of theoretical methods based on the density functional theory with hybrid functionals provides good estimates of the exchange coupling constants for polynuclear transition metal complexes. The accuracy is similar to that previously obtained for dinuclear compounds. We present test calculations on simple model systems based on H. He and CH(2). He units to compare with Hartree-Fock and multiconfigurational results. Calculations for complete, nonmodeled polynuclear transition metal complexes yield coupling constants in very good agreement with available experimental data.     

Sulla rilassazione di alcuni funzionali integrali in dimensione infinita

Summary In this work we consider the problem ()of the minimum for integral functionals I _f of the Calculus of Variations, where we don't suppose any hypothesis of convexity on the integrand and in which the state takes values in a Suslin metric space, while the last variable of the integrand is in a separable reflexive Banach space. We study two different types of relaxed problems, associated to (),and we prove that the infima of the three functionals considered are the same, that (),one of the relaxed problems, has solution and that the accumulation points of the minimizing sequences for ()are the only solutions of ().

---

---

Lavoro eseguito nell'ambito dell'Istituto per la Matematica Applicata del C.N.R., Genova.     

Mössbauer studies on one-dimensional iron phthalocyanines

Summary Magnetic moments and⁵⁷Fe Mössbauer spectra at room temperature and at liquid nitrogen temperature of polynuclear ligand-bridged iron phthalocyanines, FePcL (L = pyrazine and 4,4-bipyridyl), are reported. The experimental data are in agreement with a pseudo-octahedral environment around the iron(II) cation. Partially oxidized derivatives, FePc(pz)I_0.26 and FePc(bipy)I_1.06 have been synthesized and their⁵⁷Fe Mössbauer spectra and magnetic moments within the same temperature range obtained. Oxidation is shown to be metal centred and the iodine is found to be in I^– form for FePc(pz)_0.26 and as both I^– and I ₃ ^– species for FePc(bipy)I_1.06. While the magnetic moment of FePc(pz) increases upon oxidation, the opposite occurs for FePc(bipy).     

Synthetic erythropoietic proteins: tuning biological performance by site-specific polymer attachment

Chemical synthesis in combination with precision polymer modification allows the systematic exploration of the effect of protein properties, such as charge and hydrodynamic radius, on potency using defined, homogeneous conjugates. A series of polymer-modified synthetic erythropoiesis proteins were constructed that had a polypeptide chain similar to the amino acid sequence of human erythropoietin but differed significantly in the number and type of attached polymers. The analogs differed in charge from +5 to -26 at neutral pH and varied in molecular weight from 30 to 54 kDa. All were active in an in vitro cell proliferation assay. However, in vivo potency was found to be strongly dependent on overall charge and size. The trends observed in this study may serve as starting points for the construction of more potent synthetic EPO analogs in the future.