Structural, electronic and acid/base properties of [Ru(bpy)(bpy(OH)2)2]2+ (bpy=2,2′-bipyridine, bpy(OH)2=4,4′-dihydroxy-2,2′-bipyridine)

Charboneau, David J.; Piro, Nicholas A.; Kassel, W. Scott; Dudley, Timothy J.; Paul, Jared J.

doi:10.1016/j.poly.2015.02.001

Cited by 8 publications

(6 citation statements)

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“…The mixed metal-ligand to ligand charge transfer transitions have been noted for similar metal complexes that have increased electron-donation to the metal center upon deprotonation of attached ligands. [66][67][68]70,[85][86][87] As with the other protonation states of the complex, spectroelectrochemical data show that upon oxidation to Ru 3+ there is a decrease in intensity of the 400 to 500 nm region of the spectra and a growth of a broad band in the 600 to 1000 nm region, Fig. 7.…”

Section: Calculated Electronic Transitionsmentioning

confidence: 83%

“…70 That is, under a standard titration experiment each individual pK a value could not be determined, which has been observed for multiple complexes with hydroxyl-substituted polypyridyl ligands. 66,69,70,83,84 Unfortunately, the Pourbaix diagram is not able to de-convolute multiple deprotonation events, Fig. 4.…”

Section: Pourbaix Diagramsmentioning

confidence: 99%

“…Our previous work has focused on studying ruthenium complexes in the Ru II oxidation state. [66][67][68][69][70] Notably, as the quantity of electron-donating hydroxyl-substituted ligands increases in the series of complexes, [Ru(bpy) 3−n (44′bpy (OH) 2 ) n ] 2+ (n = 0 to 3; bpy = 2,2′-bipyridine), the Ru III/II reduction potential decreases, demonstrating that it is thermodynamically easier to reach higher oxidation states. 66 More impressively, upon deprotonation, the Ru III/II reduction potentials decrease dramatically as the ligands are able to further stabilize the higher Ru III oxidation state.…”

Section: Introductionmentioning

confidence: 99%

“…[66][67][68][69][70] Notably, as the quantity of electron-donating hydroxyl-substituted ligands increases in the series of complexes, [Ru(bpy) 3−n (44′bpy (OH) 2 ) n ] 2+ (n = 0 to 3; bpy = 2,2′-bipyridine), the Ru III/II reduction potential decreases, demonstrating that it is thermodynamically easier to reach higher oxidation states. 66 More impressively, upon deprotonation, the Ru III/II reduction potentials decrease dramatically as the ligands are able to further stabilize the higher Ru III oxidation state. This observation is seen in the extreme case where deprotonation of [Ru(44′bpy (OH) 2 ) 3 ] 2+ to [Ru(44′bpy(O − ) 2 ) 3 ] 4− results in a 1.43 V decrease in reduction potential of the Ru III/II wave in acetonitrile.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Calculated Electronic Transitionsmentioning

confidence: 83%

Section: Pourbaix Diagramsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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“…As detailed in the introduction, Fe8 is a versatile motif that can be extensively Our interest in phenol groups led us to synthesize hydroxylated ligands with the goal of preparing photo-active electron donors that can be coordinated to Fe8. Ruthenium is the obvious choice for this purpose, since it makes well-known photo-active electron donor complexes and there is already some literature on its hydroxylated polypyridine complexes [38][39][40][41]. After successfully synthesizing the tris-dihydroxybipyridine complex, we faced a synthetic logistic challenge of having six pendant phenolic groups that lead to the formation of an insoluble precipitate, the identity of which has not been determined (presumably by forming extensive intermolecular H-bonded networks).…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Fe8-based Materials as Electron Acceptors for Solar Energy Applications

Rodriguez-Santiago¹

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The urgent need to find alternative sources of energy has been recognized as a major challenge of the 21 st century. Many ideas have been proposed, but harvesting the energy of the Sun has been identified by many as the most promising alternative to satisfy the world's increasing energy demand. Among the current technologies to harness solar energy, photovoltaics and artificial photosynthesis (photocatalysis) stand out. Although very different in their strategies, both technologies entail the same core principle, the generation of a charge-separated state. To achieve the charge-separated state, both methods require an electron acceptor that will receive the photo-electron; in most cases this role is played by C60 or its derivatives. Our research group has synthesized and characterized an octanuclear iron-oxo cluster with remarkable electrochemical properties which compares favorably with the reduction potentials of C60 and derivatives. This dissertation explores the use of this octanuclear cluster as electron acceptor for solar energy applications. vii To assess the viability of Fe8 as an electron acceptor in photocatalysis, electron donors that could coordinate to its iron atoms via phenol groups were synthesized and characterized. These electron donors were used in efforts to make molecular dyads, but coordination was not achieved. The alternative strategy studied was the preparation of Fe8-based hybrid materials that can be cast with known polymer electron donors. Several hybrid materials were prepared and their general properties investigated. These materials exhibited the desired electrochemical traits as well as the general castable behavior of the polymer host. These hybrids are now ready to be tested in polymer solar cells. viii

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4,4′-Dihydroxy-2,2′-bipyridine complexes of Co(III), Cu(II) and Zn(II); structural and spectroscopic characterization

et al. 2018

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Structural, electronic and acid/base properties of [Ru(bpy)(bpy(OH)2)2]2+ (bpy=2,2′-bipyridine, bpy(OH)2=4,4′-dihydroxy-2,2′-bipyridine)

Cited by 8 publications

References 53 publications

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

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

Synthesis and Characterization of Fe8-based Materials as Electron Acceptors for Solar Energy Applications

4,4′-Dihydroxy-2,2′-bipyridine complexes of Co(III), Cu(II) and Zn(II); structural and spectroscopic characterization

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