A ruthenium water oxidation catalyst containing a bipyridine glycoluril ligand

In this work, we report the synthesis and physicochemical characterization of new chloro and aqua mononuclear Ru (II) complexes of formula [Ru(LLL)(dpp)Cl]PF6 and [Ru(LLL)(dpp)OH2](PF6)2 (LLL=tpy =2,2’ : 6’,2’’‐terpyridine; tptz=2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine and dpp=2,3‐bis(2‐pyridil)pyrazine). For the complex [Ru(tptz)(dpp)Cl]PF6, the complete structure was determined by X‐ray diffraction. Catalytic studies of aqua‐complexes revealed that they are active for the water oxidation reaction at pH 1 using cerium ammonium nitrate (CAN) as a sacrificial oxidant. Also, we were able to establish the reaction mechanism and rate constants of each stage of the catalytic cycle, turnover frequencies (TOFs), and turnover numberes (TONs). The experimental TON values for the aqua complexes were very close to the theoretical value of 7.5, indicating a high degree of recovery. DFT and TD‐DFT calculations of electronic states for all complexes were consistent with experimental results and allowed the complete assignment of their UV‐Visible bands and redox states.

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“…The Ru−Cl bond distance is 2.392(1) Å. These data agree with those reported for similar complexes [44–50] …”

Section: Resultssupporting

confidence: 90%

“…These data agree with those reported for similar complexes. [44][45][46][47][48][49][50] Scheme 2. Molecular structure of complexes (1) to (4).…”

Section: X-ray Diffractionmentioning

confidence: 99%

Synthesis and Characterization of New Mononuclear Ru (II) PolypyridylComplexes with Catalytic Activity

et al. 2023

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“…[12][13][14][15][16][17] Although a more expensive metal, ruthenium has been used as the metal of choice in many water oxidation catalysts due to the synthetic precedence and stability of these complexes. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] Mechanistic analyses have been carried out for many of these rutheniumbased catalysts. [34][35][36][37][38][39][40][41][42] A common observation is that a high oxidation state of Ru V at the catalytic metal center is required for water oxidation to occur.…”

Section: Introductionmentioning

confidence: 99%

Spectroelectrochemical studies of a ruthenium complex containing the pH sensitive 4,4′-dihydroxy-2,2′-bipyridine ligand

et al. 2018

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Attaining high oxidation states at the metal center of transition metal complexes is a key design principle for many catalytic processes. One way to support high oxidation state chemistry is to utilize ligands that are electron-donating in nature. Understanding the structural and electronic changes of metal complexes as higher oxidation states are reached is critical towards designing more robust catalysts that are able to turn over at high rates without decomposing. To this end, we report herein the changes in structural and electronic properties as [Ru(bpy)(44'bpy(OH))] is oxidized to [Ru(bpy)(44'bpy(OH))] (bpy = 2,2'-bipyridine; 44'bpy(OH) = 4,4'-dihydroxy-2,2'-bipyridine). The 44'bpy(OH) ligand is a pH-dependent ligand where deprotonation of the hydroxyl groups leads to significant electronic donation to the metal center. A Pourbaix Diagram of the complex reveals a pH independent reduction potential below pH = 2.0 for the Ru process at 0.91 V vs. Ag/AgCl. Above pH = 2.0, pH dependence is observed with a decrease in reduction potential until pH = 6.8 where the complex is completely deprotonated, resulting in a reduction potential of 0.62 V vs. Ag/AgCl. Spectroelectrochemical studies as a function of pH reveal the disappearance of the Metal to Ligand Charge Transfer (MLCT) or Mixed Metal-Ligand to Charge Transfer bands upon oxidation and the appearance of a new low energy band. DFT calculations for this low energy band were carried out using both B3LYP and M06-L functionals for all protonation states and suggest that numerous new transition types occur upon oxidation to Ru.

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“…Table 1 shows some of the determined bond lengths, which were close to those obtained for similar ruthenium complexes. 21–23 All the Ru–N and the Ru–Cl bond lengths in 1 are longer than the corresponding ones observed in the parent complex [RuCl(trpy)(bpy)](PF 6 ). 24 Additionally, the Ru1–N35 distance is higher than those reported in complexes [RuCl(trpy)(bpy-OMe)] + 25 and [Ru(trpy-OMe)(bpy)(OH 2 )] 2+ .…”

Section: Resultsmentioning

confidence: 89%

New ruthenium polypyridyl complexes as potential sensors of acetonitrile and catalysts for water oxidation

et al. 2022

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A ruthenium water oxidation catalyst containing a bipyridine glycoluril ligand

Cited by 12 publications

References 31 publications

Synthesis and Characterization of New Mononuclear Ru (II) PolypyridylComplexes with Catalytic Activity

Synthesis and Characterization of New Mononuclear Ru (II) PolypyridylComplexes with Catalytic Activity

Spectroelectrochemical studies of a ruthenium complex containing the pH sensitive 4,4′-dihydroxy-2,2′-bipyridine ligand

New ruthenium polypyridyl complexes as potential sensors of acetonitrile and catalysts for water oxidation

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