The above energy diagram can only offer a limited view of the energetics of the system, since it describes the energetics at the 3 minima only. For dynamics considerations we need more insights into the potential energy landscape. A more detailed picture of the energetics can be charted by computing the potential energy curves of the complexes along a transition coordinate that connects the optimized quintet and singlet structures. Several representative members of the series with different EW/ED properties were selected for these calculations. The nuclear coordinates for the computation of the energy curves were determined by the interpolation (and extrapolation) of distances between atom pairs, as described in the IDPP method. The obtained PESs are shown in Figure . The results are reassuring in the sense that they correspond to the above reported energy diagram, invoking that a simple shifting of the potential curves seem a good first approximation to approximate the substitution effects. Löwdin atomic charges (a.u.)