Three-Electron Two-Centered Bond and Single-Electron Transfer Mechanism of Water Splitting via a Copper–Bipyridine Complex

Gorantla, Koteswara Rao and Mallik, Bhabani Shankar (2023) Three-Electron Two-Centered Bond and Single-Electron Transfer Mechanism of Water Splitting via a Copper–Bipyridine Complex. The Journal of Physical Chemistry A, 127 (1). pp. 160-168. ISSN 1089-5639

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Abstract

We report the atomistic and electronic details of the mechanistic pathway of the oxygen-oxygen bond formation catalyzed by a copper-2,2′-bipyridine complex. Density functional theory-based molecular dynamics simulations and enhanced sampling methods were employed for this study. The thermodynamics and electronic structure of the oxygen-oxygen bond formation are presented in this study by considering the cis-bishydroxo, [CuIII(bpy)(OH)2]+, and cis-(hydroxo)oxo, [CuIV(bpy)(OH)(═O)]+, complexes as active catalysts. In the cis-bishydroxo complex, the hydroxide transfer requires a higher kinetic barrier than the proton transfer process. In the case of [CuIV(bpy)(OH)(═O)]+, the proton transfer requires a higher free energy than the hydroxide one. The peroxide bond formation is thermodynamically favorable for the [CuIV(bpy)(OH)(═O)]+ complex compared with the other. The hydroxide ion is transferred to one of the Cu-OH moieties, and the proton is transferred to the solvent. The free energy barrier for this migration is higher than that for the former transfer. From the analysis of molecular orbitals, it is found that the electron density is primarily present on the water molecules near the active sites in the highest occupied molecular orbital (HOMO) state and lowest unoccupied molecular orbital (LUMO) of the ligands. Natural bond orbital (NBO) analysis reveals the electron transfer process during the oxygen-oxygen bond formation. The σ*Cu(dxz)-O(p) orbitals are involved in the oxygen-oxygen bond formation. During the bond formation, three-electron two-centered (3e--2C) bonds are observed in [CuIII(bpy)(OH)2]+ during the transfer of the hydroxide before the formation of the oxygen-oxygen bond.

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IITH Creators:

IITH Creators	ORCiD
Mallik, Bhabani Shankar	http://orcid.org/0000-0001-9657-1497

Item Type:

Article

Uncontrolled Keywords:

Chemical bonds; Density functional theory; Electron transitions; Electron transport properties; Electronic structure; Free energy; Molecular dynamics; Molecular orbitals; Molecular oxygen; Molecules; Proton transfer;Atomistics; Bipyridines; Bond formation; Density-functional-theory; Dynamics simulation; Electron transfer mechanisms; Mechanistic pathways; Oxygen bonds; Single electron transfer; Water splitting;Copper compounds

Subjects:

Chemistry
Chemistry > Inorganic chemistry
Chemistry > Organic chemistry

Divisions:

Department of Chemistry

Depositing User:

Mr Nigam Prasad Bisoyi

Date Deposited:

16 Aug 2023 11:08

Last Modified:

16 Aug 2023 11:08

URI:

http://raiithold.iith.ac.in/id/eprint/11541