Estimation of electronic coupling in π -stacked donor-bridge-acceptor systems: correction of the two-state model

Comparison of donor-acceptor electronic couplings calculated within two-state and three-state models suggests that the two-state treatment can provide unreliable estimates of Vda because of neglecting the multistate effects. We show that in most cases accurate values of the electronic coupling in a π stack, where donor and acceptor are separated by a bridging unit, can be obtained as Ṽ da = (E2 - E1) μ12 Rda + (2 E3 - E1 - E2) 2 μ13 μ23 Rda2, where E1, E2, and E3 are adiabatic energies of the ground, charge-transfer, and bridge states, respectively, μij is the transition dipole moments between the states i and j, and Rda is the distance between the planes of donor and acceptor. In this expression based on the generalized Mulliken-Hush approach, the first term corresponds to the coupling derived within a two-state model, whereas the second term is the superexchange correction accounting for the bridge effect. The formula is extended to bridges consisting of several subunits. The influence of the donor-acceptor energy mismatch on the excess charge distribution, adiabatic dipole and transition moments, and electronic couplings is examined. A diagnostic is developed to determine whether the two-state approach can be applied. Based on numerical results, we showed that the superexchange correction considerably improves estimates of the donor-acceptor coupling derived within a two-state approach. In most cases when the two-state scheme fails, the formula gives reliable results which are in good agreement (within 5%) with the data of the three-state generalized Mulliken-Hush model

Diradicals acting through diamagnetic phenylene vinylene bridges: Raman spectroscopy as a probe to characterize spin delocalization

We present a complete Raman spectroscopic study in two structurally well-defined diradical species of different lengths incorporating oligo p-phenylene vinylene bridges between two polychlorinated triphenylmethyl radical units, a disposition that allows sizeable conjugation between the two radicals through and with the bridge. The spectroscopic data are interpreted and supported by quantum chemical calculations. We focus the attention on the Raman frequency changes, interpretable in terms of: (i) bridge length (conjugation length); (ii) bridge conformational structure; and (iii) electronic coupling between the terminal radical units with the bridge and through the bridge, which could delineate through-bond spin polarization, or spin delocalization. These items are addressed by using the"oligomer approach" in conjunction with pressure and temperature dependent Raman spectroscopic data. In summary, we have attempted to translate the well-known strategy to study the electron (charge) structure of π−conjugated molecules by Raman spectroscopy to the case of electron (spin) interactions via the spin delocalization mechanism.

When ESDP confronts ENP: security sector reform as a bridge in the EU’s foreign policy

The European Neighbourhood Policy’s birth has taken place in parallel with the renewed momentum of the European Security and Defence Policy, which has launched 14 operations since 2003. Both policies’ instruments have converged in the neighbouring area covered by ENP: Georgia, in the East and the Palestinian Territories in the South. In both cases, the Security Sector Reform strategies have been the main focus for ESDP and an important objective for ENP. In this paper, two objectives are pursued: first, to assess the EU’s involvement in both cases in SSR terms; and second, to analyse whether the convergence of ESDP operations with a broader EU neighbourhood policy implies that the former has become an instrument for the a EU external action.

Explaining Variation in Organizational Change: The Reform of Human Resource Management in the European Commission and the OECD

In this article we investigate the reforms of human resource management in the European Commission and the OECD by analyzing comparatively to what extent both organizations have adjusted their respective structures towards the ideal type of the so-called New Public Management (NPM). The empirical findings show that reforms towards NPM are more pronounced in the Commission than in the OECD. These findings are surprising for two reasons: First, it seems rather paradoxical that the OECD as central promoter of NPM at the international level lags behind the global trend when it comes to reforming its own structures. Second, this result is in contradiction with theoretical expectations, as they can be derived from theories of institutional isomorphism. To nevertheless account for the surprising results, it is necessary to modify and complement existing theories especially with regard to the scope conditions of their causal mechanisms.

Is the Spanish Inheritance and Gift Tax incompatible with the free movement of workers and capital?: The reasoned opinion of the EU Commission IP/10/513

The aim of my speech is answering to the question if the Spanish Inheritance and Gift Tax is incompatible with the free movement of workers and capital. We are going to pay special attention to the European Commission’s request to Spain to change its Inheritance and Gift Tax provisions for Non-Residents or Assets held abroad. In order to answer to the question mentioned above five points will be explained. At first place I am going to describe the infrengement procedure established in the Article 258 that the EU Commission can follow when a Member State doesn’t comply with Community Law. At second place, we are going to explain what is the content of the EU Commission delivered on 5th of may 2010 regarding the spanish Inheritance and Gift Tax. Then, we will analise what establishes the Community Law regarding the freedom of workers and capital and how they are understood by the EU Court of Justice in similar cases. Finally, we are going to provide possible amendments that Spain could undertake.

Respuesta no lineal y criterios de diseño de puentes arco espaciales

El desarrollo más reciente de los puentes arco ha llevado a una nueva tipología: los “puentes arco espaciales”. Se entiende por puente arco espacial todo puente arco en el que, por su configuración geométrica y estructural, las cargas gravitatorias generan esfuerzos no contenidos en el plano del arco. Por un lado, aparecen para satisfacer las necesidades funcionales cuando estructuras en arco resultan las más adecuadas para sostener tableros curvos y evitar así apoyos intermedios. Desde un punto de vista estético, surgen como demanda de los nuevos puentes en entornos urbanos, buscando, no sólo una forma cuidada, sino persiguiendo convertirse en emblemas de la ciudad a partir de la originalidad y la innovación. Su proyecto y construcción es posible gracias a las grandes posibilidades que ofrecen los nuevos métodos de cálculo y dibujo por ordenador, en los que, a través del incremento de memoria y rapidez, cada vez se emplean programas más completos y nuevas modelizaciones, más cercanas a la realidad. No menos importante es el desarrollo de los medios auxiliares de construcción y de las herramientas de CAD/CAM, que convierte en construibles por control numérico formas de manufactura impensables. Ello trasciende en infinitas posibilidades de diseño y estructura. Sin embargo, el diseño y construcción de estas nuevas tipologías no ha estado acompañado por el avance en el estado del conocimiento fundamentado en la investigación, ya que se han desarrollado pocos estudios que explican parcialmente la respuesta estructural de estos puentes. Existe, por lo tanto, la necesidad de profundizar en el estado del conocimiento y clarificar su respuesta estructural, así como de plantear, finalmente, criterios de diseño que sirvan de apoyo en las fases de concepción y de proyecto a estas nuevas tipologías.

Institutional Balance in the EU. The Prodi Administration as a Reforming Commission

The essay looks at the Prodi Commission (1999-2004) in the context of the institutional balance in the European Union. Not only did Prodi come into office at a time of unprecedented weakness of the Executive, but the Commission operates within a changing institutional equilibrium, one made more precarious by the shifting political disposition of the Member States