Ru-Ow3 approach Sample Clauses

Ru-Ow3 approach. In the first AIMD simulation for this approach the [(Benzene)Ru(O)(bpy)]2+ complex plus three water molecules are included: w1, w2 close to the oxyl radical and w3 at 3.5 Å from the Ruthenium atom on the opposite side (see Figure 4.2). The collective variable (CV) used in this simulation is the Ru-Ow3 distance with a maximum allowed value of 3.7 Å. In Figure 4.3 the Ru-Ow3 and the Ru-benzene distances along the AIMD trajectory are shown. The benzene breaks its coordination bond when the incoming water enters the coordination shell of the metal (Ru-Ow3≈2.7 Å), suggesting that this pathway is unfeasible. It should be pointed out that the biasing potential builds up also when the water is coordinated to the Ru (see Figure 4.3, after about 1 ps). This is why the water eventually leaves the Ru coordination shell in the second part of the trajectory. In order to check if the observed structural instability of the catalyst is related to the specific choice of the aromatic ligand, or to the missing water environment, additional simulations using the same setup were performed: First the benzene ligand was substituted with hexamethylbenzene and cymene and then the same reaction path was analysed in vacuum. In addition the benzene was reconsidered in a water solvated environment. In all these simulations a similar behaviour with the aromatic ligand leaving the coordination shell of the metal is present. In Figure 4.3 the results obtained in vacuum and in solvated environment for the benzene case are shown. The simulations reveal how the degradation of the catalyst is very similar in both cases, with the water environment only slightly slowing down the process. It can be concluded that the heptacoordinated form of the Ruthenium is not stable for this class of catalysts.