An Electron Dynamics Mechanism of Charge Separation in the Initial‐Stage Dynamics of Photoinduced Water Splitting in XMnWater (X=OH, OCaH) and Electron–Proton Acceptors

Abstract

An electron dynamics mechanism of charge separation in the initial stage of excited-state reactions of the class of XMnOH2 ⋅⋅⋅A${ \to }$XMnOH⋅⋅⋅HA (X=OH or OCaH; A=N-methylformamidine, guanidine, imidazole, or ammonia cluster) is reported. The dynamic effect of calcium doping is also revealed. This study provides a novel factor to be considered in designing efficient systems for photoinduced water splitting.

Photoinduced Charge Separation Catalyzed by Manganese Oxides onto a Y‐Shaped Branching Acceptor Efficiently Preventing Charge Recombination

“…The EPDs of these types were also studied extensively in our previous study, [2] through which we revealed the roles of doped Ca atoms, which 1) suppress the annihilation process of the created charges eparation in the EPA, and 2) modulate the channels of the pathway of electron flow. [1,2] Here, we therefore examined whether these are actually true of the Y-shaped acceptor.S ystemsA1a nd A2 have been designed to be small enought oa llow us to perform fulldimensional nonadiabatic electron dynamics. The EA (H T1 OÀ C 6 H 4 ÀNH 3 + )a nd PA ([C 3 N 2 H 3 ] À )c omponents are used both in systemsA1a nd A2.…”

“…In our previous studies, we have conceived aq uantum mechanical mechanism of charge separation by Mn oxides, [1,2] which can be summarized as follows [Eq. (2)]:…”

“…Note that W here was represented as XÀMn in previousstudies. [1,2] The symbols "···", "C", and "*" indicate hydrogen bond, unpaired electron (radical), and the excited electronic state, respectively.H D + represents ap roton with ap artial positive charget ot he extent of 0.5 e, whereas A DÀ C represents an anion radical with ap artial chargeo ft he magnitude of À0.5 e. W denotes an arbitrary Mn oxide (complex), but is chosen to keep the system simple and stable. Ai sap roton-electron acceptor that has low-lying Rydberg-like excited states.…”

“…We have discussed the role of Ca atoms in this respect. [1,2] 3) Electrons andp rotons are to be physically carried to their individual destinations to accomplish their primary roles. Therefore, the accepting subsystem should have at rack-branching function to carry these particles separately.…”

Maximal orbital analysis of molecular wavefunctions

“…For example, Nagashima and Takatsuka reported recently a description of proton transfer in an excited state of phenol in ammonia and showed an orbital with strong Rydberg character playing a critical role in the reaction, suggesting that this findings calls for a novel fundamental description of excited state proton transfer. We believe that the MOA analysis will capture the change in orbital character along the reaction pathway, and provide a quantitative description of orbital interactions that come into play …”