Proton hole

Figure 7-4. Excess coordination number plots for (a) MEP (three-water-bridge) [27] and (b) PMF (H64 in ) [14] simulations for the proton transfer in CAII. Note that the MEP calculation follows a very concerted mechanism while PMF simulation follows a step-wise proton hole mechanism...

Figure 2.5 Relative energetics of the Grotthuss and proton-hole-transfer mechanisms as a function of the )Ka values. (Reproduced with permission from ref. 30.)...

Y has a full g9/2 shell for neutrons and one neutron in the d5/2 shell, and one proton-hole in the f-p shell. We describe in the model space... 

A single crystal X-ray structure of a free-base corrole was obtained in 1971, and is shown below in Figure 2.1.3. Based upon this structure and upon molecular calculations, free-base corrole was determined to bear a proton hole at N(22) (as drawn for 2.4), with the other three nitrogen atoms protonated. Where appropriate throughout this discussion, the corrole framework will be shown in this manner. This does not mean, however, that a specific location is being designated for what are, presumably, highly delocalized double bonds. 

In Section A, we have already considered the approach that includes the movement of two types of faults ionic state (positive or/and negative) and Bjerrum faults. It has been suggested (see also, e.g., Refs. 158-160) that the drift of the ionic state (i.e., strictly speaking, an excess proton or proton hole) along the ordering chain changes the polarization of each site and therefore changes the polarization of the whole chain. 

A SrTio.4 Mgo.603 x catalyst was used, which had been previously shown to be an effective catalyst for this reaction. The use of the membrane significantly increased the yield of C2 hydrocarbons. This remains an area with significant unexplored potential. Progress can be made here by developing CMR systems with enhanced catalytic activities towards the CH4 coupling reaction, and asymmetric-type proton-hole or proton-electron conducting membranes with significantly increased conductivities. 

Hamakawa S, Hibino T, Iwahara H. Electrochemical hydrogen permeation in a proton-hole mixed conductor and its application to a membrane reactor. J Electrochem Soc. 1994 141(7) 1720. 

In seeking activated states relevant to proton conduction, a proton-hole defect was introduced intermittently and, thereafter, restored. This protocol led to the formation of a metastable intermediate state with two delocahzed protons, as depicted in Fig. 4. One proton is delocalized between the two oxygen atoms in a Zundel-ion (H502" ). Two neighboring sulfonate groups re-arrange in order to accommodate a second proton between them. Overall, the reorganization occurs within 2 ps of the creation of the defect. It was observed... 

Fig. 4.2 Update criterion for a proton transfer of a an excess proton and b a proton-hole. As soon as the ratio p between the projected donor-hydrogen distance Hr gll and the donor-acceptor distance rDA exceeds the preset threshold p, the proton transfer event is registered as a successful exchange. Registered proton transfer events observed in MD simulations of c IM HCl and d IM NaOH obtained for the recommended threshold ratio 0.585. Horizontal lines eorrespond to periods where water molecules carry an excess proton forming a ion (HCl) or a...

---