Chemical and Visible‐Light‐Driven Water Oxidation by Iron Complexes at pH 7–9: Evidence for Dual‐Active Intermediates in Iron‐Catalyzed Water Oxidation

Abstract

Ironing out a solution: Chemical and visible‐light‐driven water oxidation by iron complexes and iron salts at pH 7–9 has been investigated. The iron complexes and salts act as precatalysts (see scheme) to produce α‐Fe2O3 nanoparticles that are the real catalyst for the water oxidation with a turnover number over 1000.

Iron Complexes of Square Planar Tetradentate Polypyridyl-Type Ligands as Catalysts for Water Oxidation

“…10 Lau and coworkers have suggested that at low pH multidentate N-donor iron complexes accomplish water oxidation through a molecular iron-oxo intermediate. 11 At high pH, however, they claim that ligand dissociation occurs to generate Fe 2 O 3 nanoparticles that catalyze water oxidation.…”

Molecular complexes in water oxidation: Pre-catalysts or real catalysts

“…It is usually applied to monitor the formation of metal oxide/hydroxide or other insoluble particles in reaction solutions [23][24][25].…”

“…22a-d) with oxidant [Ru(bpy) 3 ](ClO 4 )3 in borate buffer at pH 8.5[25]. It was found that, all of the complexes except Fe(mcp)Cl 2 (20b-2Cl) showed the activity in chemical water oxidation[30].…”

“…Upon irradiation, particles began to appear and their size increased with irradiation time. After particles formed during photocatalytic water oxidation were collected, EDX and XPS found that the particles are Fe 2 O 3 by elemental analysis qualitative and quantitative[25]. As compared to DLS used for solution sample, TEM and SEM are commonly used for the sample deposited on solid supports to observe the surface morphology in nanoscale.…”

Synthesis and catalytic properties of an iron(III) complex supported by amine-bis(phenolate) ligand

“…Although, there has been significant progress in designing molecular catalysts for H 2 evolution, the search for highly active catalysts that can operate in aqueous solution still remains a challenge. In general, iron(III) complexes are employed as electrocatalysts for water oxidation [26][27][28][29][30], but there are few reports on water reduction by iron(III) complexes [31]. Herein, we present the synthesis and characterization of an iron complex, [LFeCl] 1, as well as its catalytic properties.…”