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Outer Coordination Spheres Engineering of Ru-based Molecular Water Oxidation Catalysts

Time: Fri 2022-04-08 14.00

Location: F3, Lindstedtsvägen 26 & 28, Stockholm

Video link:

Language: English

Subject area: Chemistry

Doctoral student: Tianqi Liu , Organisk kemi, Molekylär elektronik, CMD, Licheng Sun

Opponent: Professor Julio Lloret-Fillol, Institute of Chemical Research of Catalonia (ICIQ)

Supervisor: Professor Licheng Sun, Molekylär elektronik, CMD, Organisk kemi

QC 2022-03-08


The outer coordination sphere plays a vital role in metalloenzyme catalysis, while this principle is relatively less considered in the design of man-made molecular catalysts. This thesis investigates the role of outer coordination spheres in water oxidation by a series of ruthenium-based complexes.

The first chapter presents an overview of the development of molecular water oxidation catalysts, mainly focusing on ruthenium-based complexes. Moreover, the strategies used to modulate the inner and outer coordination spheres are also summarized.

The second chapter clarifies the role of electronic effects and hydrophobic interactions in Ru-bda-type catalysts. Electronic effects are found to be the less-dominating parameter for the catalytic activity and mechanism, while hydrophobic interactions play an important role in catalysis. The third chapter focuses on the switch in mechanism with Ru-pda-type catalysts through strengthening of the π-π interactions between the axial ligands.

The fourth chapter discusses a crystal structure of the long-proposed pseudo-seven-coordinate RuIII-aqua complex where the aqua ligand is stabilized by the distal ligand. The obtained complex enables us to visualize how the catalyst grasps the incoming aqua ligands at the initial catalytic step. Based on this catalytic model, four catalysts with well-defined outer coordination spheres are synthesized, and the influence of hydrophilic/hydrophobic outer spheres on water oxidation is discussed in chapter five.

In general, this thesis follows the transition of the outer coordination sphere engineering from coordinated ligand modifications to remote substituent modulations.