Carlos Gallego

Substitution reactions on cyclometallated Pt(IV) complexes; a kinetic survey of the bond strength of PtS, N, and P-based ligands

Abstract The substitution reactions of a series of sulfur, nitrogen and phosphorus-based ligands (L) on Pt(IV) complexes having a chloride ligand, the cyclometallated imine ligand CC5Cl4CHNCH2C6H5, and two methyl groups and the leaving ligand in a mer-geometrical arrangement, [Pt(C∧N)(CH3)2Cl(L)], have been studied as a function of temperature, solvent, and electronic and steric characteristics of the leaving ligands. Although in all cases a limiting dissociative mechanism has been found to apply, where the dissociation of the leaving ligand corresponds to the rate-determining step, the relative values of the different rate constants involved in the process, i.e. dissociation/association of the leaving/entering ligands and the effect of the solvent, change dramatically in the systems studied. The results agree with the previously determined mechanism operating on these substitution reactions, and serve as a very good measure of the strength of the PtL bond, which is influenced by both electronic and steric characteristics. The possible solvent-assisted hydrogen bonding of the leaving ligand with the rest of the molecule is made also evident in the relevant situations. The equilibrium constants detected for some of the systems indicate that, although Pt(IV) complexes are expected to be hard acids and prefer nitrogen to sulfur or phosphorus donors, this is not so. This result is in line with the softening of the nature of the Pt(IV) centres of complexes containing several PtC bonds.

Análisis multi-criterio para evaluar la capacidad de absorción de energía de tubos fabricados con láminas de metal expandido y sólidas

espanolUn analisis multi-criterio ha sido desarrollado para evaluar la capacidad de absorcion de energia de tubos circulares fabricados con laminas de metal expandido y laminas solidas. Mediante un Proceso de Jerarquia Analitica (AHP - Analytic Hierarchy Process) se asignaron de peso a diferentes parametros de carga y resistencia de impacto. Posteriormente, estos pesos han sido luego atribuidos a una Evaluacion Proporcional Compleja (COPRAS - Complex Proportional Assessment) para seleccionar la mejor opcion entre seis alternativas disponibles. Los resultados muestran que los tubos circulares fabricados con laminas de metal expandido y celdas individuales con orientacion α=0o presentan caracteristicas favorables para absorber energia de forma controlada y estable asi como eficientes parametros de diseno estructural. La metodologia de analisis multi-criterio constituye una valiosa herramienta en los procesos de toma de decisiones para la seleccion de dispositivos empleados en aplicaciones de absorcion de energia. EnglishA multi-criteria analysis has been developed to evaluate the energy absorption of round tubes made with expanded metal sheets and solid sheets. Throughout an AHP (Analytic Hierarchy Process) the assignation of the weight to different load parameter and impact resistance were given. Thereafter, these weights were then attributed to the COPRAS method (Complex Proportional Assessment) to select the best alternative among the available options. The results show that the circular tubes made with deployed metal sheets and individual cells with orientation α=0o present favorable characteristics to absorb energy in a controlled and stable way as well as efficient structural design parameters. Multi-criteria analysis methodology is a valuable support for decision making processes to the selection of devices used in energy absorbing applications.