Ruthenium complexes with asymmetric hydroxy- and methoxy-substituted bipyridine ligands

Kaitlyn R. Benson; Jaqueline Stash; Katherine L. Moffa; Russell H. Schmehl; Timothy J. Dudley; Jared J. Paul

doi:10.1016/j.poly.2021.115300

Ruthenium complexes with asymmetric hydroxy- and methoxy-substituted bipyridine ligands

Kaitlyn R. Benson, Jaqueline Stash, Katherine L. Moffa, Russell H. Schmehl, Timothy J. Dudley, Jared J. Paul

Math, Science, and Technology

Research output: Contribution to journal › Article › peer-review

4 Scopus citations

Abstract

The development of metal complexes with ligands capable of proton transfer can result in significant advances in Proton Coupled Electron Transfer (PCET) chemistry, specifically understanding how these reactions occur mechanistically in the excited state. The synthesis of three ruthenium complexes containing asymmetric bipyridine ligands: [Ru(bpy)₂(4bpyOH)]²⁺, [Ru(bpy)₂(4bpyOMe)]²⁺, and [Ru(bpy)₂(44′bpy(OH)(OMe))]²⁺ (bpy = 2,2′-bipyridine; 4bpyOH = 4-hydroxy-2,2′-bipyridine; 4bpyOMe = 4-methoxy-2,2′-bipyridine; 44′bpy(OH)(OMe) = 4-hydroxy-4′-methoxy-2,2′-bipyridine) are reported. These complexes were studied using both experimental and computational methods. These studies indicate that the methoxy-substitution gives similar electron-donating properties to the hydroxy-substitution, meaning that the methoxy-substitution is a good control when examining electron transfer in the absence of proton transfer. Potential versus pH diagrams show that [Ru(bpy)₂(4bpyOH)]²⁺ has a Ru^III/II reduction potential of 0.97 V vs. Ag/AgCl in aqueous acidic solution that decreases to 0.76 V vs. Ag/AgCl when deprotonated. The [Ru(bpy)₂(44′bpy(OH)(OMe))]²⁺, with an additional methoxy-substituent, has a Ru^III/II reduction potential that is slightly lower with a potential of 0.92 V vs. Ag/AgCl in acidic aqueous solution that decreases to 0.74 V vs. Ag/AgCl when deprotonated. These complexes are comparable to other hydroxy- and methoxy-substituted polypyridyl ruthenium complexes reported previously, showing the additive effects of hydroxy- and methoxy-substitutions on the reduction potential of the Ru^III/II wave and spectroscopic shifts that occur as the ligand scaffold is altered.

Original language	English (US)
Article number	115300
Journal	Polyhedron
Volume	205
DOIs	https://doi.org/10.1016/j.poly.2021.115300
State	Published - Sep 1 2021

Bibliographical note

Funding Information:
Funding for this project comes from a grant from the National Science Foundation – Chemical Structure, Dynamics & Mechanisms B (CHE-1900536). This work was also supported by two Major Research Instrumentation grants from the National Science Foundation ( CHE-1827930 and CHE-2018399 ). Support from the College of Liberal Arts and Sciences at Villanova University is gratefully acknowledged. Thank you to Mark Olson for running mass spectrometry samples. This work is dedicated to Robert L. Paul.

Funding Information:
Funding for this project comes from a grant from the National Science Foundation – Chemical Structure, Dynamics & Mechanisms B (CHE-1900536). This work was also supported by two Major Research Instrumentation grants from the National Science Foundation (CHE-1827930 and CHE-2018399). Support from the College of Liberal Arts and Sciences at Villanova University is gratefully acknowledged. Thank you to Mark Olson for running mass spectrometry samples. This work is dedicated to Robert L. Paul.

Publisher Copyright:
© 2021 Elsevier Ltd

Keywords

Bipyridine
Hydroxy
Methoxy
PCET
Ruthenium

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10.1016/j.poly.2021.115300

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title = "Ruthenium complexes with asymmetric hydroxy- and methoxy-substituted bipyridine ligands",

abstract = "The development of metal complexes with ligands capable of proton transfer can result in significant advances in Proton Coupled Electron Transfer (PCET) chemistry, specifically understanding how these reactions occur mechanistically in the excited state. The synthesis of three ruthenium complexes containing asymmetric bipyridine ligands: [Ru(bpy)2(4bpyOH)]2+, [Ru(bpy)2(4bpyOMe)]2+, and [Ru(bpy)2(44′bpy(OH)(OMe))]2+ (bpy = 2,2′-bipyridine; 4bpyOH = 4-hydroxy-2,2′-bipyridine; 4bpyOMe = 4-methoxy-2,2′-bipyridine; 44′bpy(OH)(OMe) = 4-hydroxy-4′-methoxy-2,2′-bipyridine) are reported. These complexes were studied using both experimental and computational methods. These studies indicate that the methoxy-substitution gives similar electron-donating properties to the hydroxy-substitution, meaning that the methoxy-substitution is a good control when examining electron transfer in the absence of proton transfer. Potential versus pH diagrams show that [Ru(bpy)2(4bpyOH)]2+ has a RuIII/II reduction potential of 0.97 V vs. Ag/AgCl in aqueous acidic solution that decreases to 0.76 V vs. Ag/AgCl when deprotonated. The [Ru(bpy)2(44′bpy(OH)(OMe))]2+, with an additional methoxy-substituent, has a RuIII/II reduction potential that is slightly lower with a potential of 0.92 V vs. Ag/AgCl in acidic aqueous solution that decreases to 0.74 V vs. Ag/AgCl when deprotonated. These complexes are comparable to other hydroxy- and methoxy-substituted polypyridyl ruthenium complexes reported previously, showing the additive effects of hydroxy- and methoxy-substitutions on the reduction potential of the RuIII/II wave and spectroscopic shifts that occur as the ligand scaffold is altered.",

keywords = "Bipyridine, Hydroxy, Methoxy, PCET, Ruthenium",

author = "Benson, {Kaitlyn R.} and Jaqueline Stash and Moffa, {Katherine L.} and Schmehl, {Russell H.} and Dudley, {Timothy J.} and Paul, {Jared J.}",

note = "Funding Information: Funding for this project comes from a grant from the National Science Foundation – Chemical Structure, Dynamics & Mechanisms B (CHE-1900536). This work was also supported by two Major Research Instrumentation grants from the National Science Foundation ( CHE-1827930 and CHE-2018399 ). Support from the College of Liberal Arts and Sciences at Villanova University is gratefully acknowledged. Thank you to Mark Olson for running mass spectrometry samples. This work is dedicated to Robert L. Paul. Funding Information: Funding for this project comes from a grant from the National Science Foundation – Chemical Structure, Dynamics & Mechanisms B (CHE-1900536). This work was also supported by two Major Research Instrumentation grants from the National Science Foundation (CHE-1827930 and CHE-2018399). Support from the College of Liberal Arts and Sciences at Villanova University is gratefully acknowledged. Thank you to Mark Olson for running mass spectrometry samples. This work is dedicated to Robert L. Paul. Publisher Copyright: {\textcopyright} 2021 Elsevier Ltd",

year = "2021",

month = sep,

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doi = "10.1016/j.poly.2021.115300",

language = "English (US)",

volume = "205",

journal = "Polyhedron",

issn = "0277-5387",

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TY - JOUR

T1 - Ruthenium complexes with asymmetric hydroxy- and methoxy-substituted bipyridine ligands

AU - Benson, Kaitlyn R.

AU - Stash, Jaqueline

AU - Moffa, Katherine L.

AU - Schmehl, Russell H.

AU - Dudley, Timothy J.

AU - Paul, Jared J.

N1 - Funding Information: Funding for this project comes from a grant from the National Science Foundation – Chemical Structure, Dynamics & Mechanisms B (CHE-1900536). This work was also supported by two Major Research Instrumentation grants from the National Science Foundation ( CHE-1827930 and CHE-2018399 ). Support from the College of Liberal Arts and Sciences at Villanova University is gratefully acknowledged. Thank you to Mark Olson for running mass spectrometry samples. This work is dedicated to Robert L. Paul. Funding Information: Funding for this project comes from a grant from the National Science Foundation – Chemical Structure, Dynamics & Mechanisms B (CHE-1900536). This work was also supported by two Major Research Instrumentation grants from the National Science Foundation (CHE-1827930 and CHE-2018399). Support from the College of Liberal Arts and Sciences at Villanova University is gratefully acknowledged. Thank you to Mark Olson for running mass spectrometry samples. This work is dedicated to Robert L. Paul. Publisher Copyright: © 2021 Elsevier Ltd

PY - 2021/9/1

Y1 - 2021/9/1

N2 - The development of metal complexes with ligands capable of proton transfer can result in significant advances in Proton Coupled Electron Transfer (PCET) chemistry, specifically understanding how these reactions occur mechanistically in the excited state. The synthesis of three ruthenium complexes containing asymmetric bipyridine ligands: [Ru(bpy)2(4bpyOH)]2+, [Ru(bpy)2(4bpyOMe)]2+, and [Ru(bpy)2(44′bpy(OH)(OMe))]2+ (bpy = 2,2′-bipyridine; 4bpyOH = 4-hydroxy-2,2′-bipyridine; 4bpyOMe = 4-methoxy-2,2′-bipyridine; 44′bpy(OH)(OMe) = 4-hydroxy-4′-methoxy-2,2′-bipyridine) are reported. These complexes were studied using both experimental and computational methods. These studies indicate that the methoxy-substitution gives similar electron-donating properties to the hydroxy-substitution, meaning that the methoxy-substitution is a good control when examining electron transfer in the absence of proton transfer. Potential versus pH diagrams show that [Ru(bpy)2(4bpyOH)]2+ has a RuIII/II reduction potential of 0.97 V vs. Ag/AgCl in aqueous acidic solution that decreases to 0.76 V vs. Ag/AgCl when deprotonated. The [Ru(bpy)2(44′bpy(OH)(OMe))]2+, with an additional methoxy-substituent, has a RuIII/II reduction potential that is slightly lower with a potential of 0.92 V vs. Ag/AgCl in acidic aqueous solution that decreases to 0.74 V vs. Ag/AgCl when deprotonated. These complexes are comparable to other hydroxy- and methoxy-substituted polypyridyl ruthenium complexes reported previously, showing the additive effects of hydroxy- and methoxy-substitutions on the reduction potential of the RuIII/II wave and spectroscopic shifts that occur as the ligand scaffold is altered.

AB - The development of metal complexes with ligands capable of proton transfer can result in significant advances in Proton Coupled Electron Transfer (PCET) chemistry, specifically understanding how these reactions occur mechanistically in the excited state. The synthesis of three ruthenium complexes containing asymmetric bipyridine ligands: [Ru(bpy)2(4bpyOH)]2+, [Ru(bpy)2(4bpyOMe)]2+, and [Ru(bpy)2(44′bpy(OH)(OMe))]2+ (bpy = 2,2′-bipyridine; 4bpyOH = 4-hydroxy-2,2′-bipyridine; 4bpyOMe = 4-methoxy-2,2′-bipyridine; 44′bpy(OH)(OMe) = 4-hydroxy-4′-methoxy-2,2′-bipyridine) are reported. These complexes were studied using both experimental and computational methods. These studies indicate that the methoxy-substitution gives similar electron-donating properties to the hydroxy-substitution, meaning that the methoxy-substitution is a good control when examining electron transfer in the absence of proton transfer. Potential versus pH diagrams show that [Ru(bpy)2(4bpyOH)]2+ has a RuIII/II reduction potential of 0.97 V vs. Ag/AgCl in aqueous acidic solution that decreases to 0.76 V vs. Ag/AgCl when deprotonated. The [Ru(bpy)2(44′bpy(OH)(OMe))]2+, with an additional methoxy-substituent, has a RuIII/II reduction potential that is slightly lower with a potential of 0.92 V vs. Ag/AgCl in acidic aqueous solution that decreases to 0.74 V vs. Ag/AgCl when deprotonated. These complexes are comparable to other hydroxy- and methoxy-substituted polypyridyl ruthenium complexes reported previously, showing the additive effects of hydroxy- and methoxy-substitutions on the reduction potential of the RuIII/II wave and spectroscopic shifts that occur as the ligand scaffold is altered.

KW - Bipyridine

KW - Hydroxy

KW - Methoxy

KW - PCET

KW - Ruthenium

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U2 - 10.1016/j.poly.2021.115300

DO - 10.1016/j.poly.2021.115300

M3 - Article

AN - SCOPUS:85108004777

SN - 0277-5387

VL - 205

JO - Polyhedron

JF - Polyhedron

M1 - 115300

ER -

Ruthenium complexes with asymmetric hydroxy- and methoxy-substituted bipyridine ligands

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