Ligand exchange upon oxidation of a dinuclear Mn complex-detection of structural changes by FT-IR spectroscopy and ESI-MS

Gerriet Eilers, Camilla Zettersten, Leif Nyholm, Leif Hammarström, Reiner Lomoth

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

The structural rearrangements triggered by oxidation of the dinuclear Mn complex [Mn2(bpmp)(μ-OAc)2]+ (bpmp = 2,6-bis[bis(2-pyridylmethyl)amino]methyl-4-methylphenol anion) in the presence of water have been studied by combinations of electrochemistry with IR spectroscopy and with electrospray ionization mass spectrometry (ESI-MS). The exchange of acetate bridges for water (D2O) derived ligands in different oxidation states could be monitored by mid-IR spectroscopy in CD 3CN-D2O mixtures following the vas(c-o) bands of bound acetate at 1594.4 cm-1 (II,II), 1592.0 cm-1 (II,III) and 1586.5 cm-1 (III,III). Substantial loss of bound acetate occurs at much lower water content (<0.5% v/v) in the III,III state than in the II,II and II,III states (≥10%). The ligand-exchange reactions do not initially reduce the overall charge of the complex but facilitate further oxidation by proton-coupled electron transfer as the water-derived ligands are increasingly deprotonated in higher oxidation states. In the IR spectra deprotonation could be followed by the formation of acetic acid (DOAc, ∼1725 cm-1, v(c-o)) from the released acetate (1573.6 cm -1, vas(c-o)). By the on-line combination of an electrochemical flow cell with ESI-MS several product complexes could be identified. A di-μ-oxo bridged III,IV dimer [Mn2(bpmp)(μ-O) 2]2+ (m/z 335.8) can be generated at potentials below the III,III/II,III couple of the di-μ-acetato complex (0.61 V vs. ferrocene). The ligand-exchange reactions allow for three metal-centered oxidation steps to occur from II,II to III,IV in a potential range of only 0.5 V, explaining the formation of a spin-coupled III,IV dimer by photo-oxidation with [Ru[bpy) 3]3+ in previous EPR studies.

Original languageEnglish
Pages (from-to)1033-1041
Number of pages9
JournalDalton Transactions
Issue number6
DOIs
Publication statusPublished - Mar 21 2005

Fingerprint

Electrospray ionization
Mass spectrometry
Infrared spectroscopy
Ion exchange
Ligands
Acetates
Oxidation
Dimers
Water
Deprotonation
Photooxidation
Electrochemistry
Acetic Acid
Water content
Anions
Paramagnetic resonance
Protons
Metals
Electrons

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Ligand exchange upon oxidation of a dinuclear Mn complex-detection of structural changes by FT-IR spectroscopy and ESI-MS. / Eilers, Gerriet; Zettersten, Camilla; Nyholm, Leif; Hammarström, Leif; Lomoth, Reiner.

In: Dalton Transactions, No. 6, 21.03.2005, p. 1033-1041.

Research output: Contribution to journalArticle

Eilers, Gerriet ; Zettersten, Camilla ; Nyholm, Leif ; Hammarström, Leif ; Lomoth, Reiner. / Ligand exchange upon oxidation of a dinuclear Mn complex-detection of structural changes by FT-IR spectroscopy and ESI-MS. In: Dalton Transactions. 2005 ; No. 6. pp. 1033-1041.
@article{61ad14ce0acc47d489b334e34dfc7252,
title = "Ligand exchange upon oxidation of a dinuclear Mn complex-detection of structural changes by FT-IR spectroscopy and ESI-MS",
abstract = "The structural rearrangements triggered by oxidation of the dinuclear Mn complex [Mn2(bpmp)(μ-OAc)2]+ (bpmp = 2,6-bis[bis(2-pyridylmethyl)amino]methyl-4-methylphenol anion) in the presence of water have been studied by combinations of electrochemistry with IR spectroscopy and with electrospray ionization mass spectrometry (ESI-MS). The exchange of acetate bridges for water (D2O) derived ligands in different oxidation states could be monitored by mid-IR spectroscopy in CD 3CN-D2O mixtures following the vas(c-o) bands of bound acetate at 1594.4 cm-1 (II,II), 1592.0 cm-1 (II,III) and 1586.5 cm-1 (III,III). Substantial loss of bound acetate occurs at much lower water content (<0.5{\%} v/v) in the III,III state than in the II,II and II,III states (≥10{\%}). The ligand-exchange reactions do not initially reduce the overall charge of the complex but facilitate further oxidation by proton-coupled electron transfer as the water-derived ligands are increasingly deprotonated in higher oxidation states. In the IR spectra deprotonation could be followed by the formation of acetic acid (DOAc, ∼1725 cm-1, v(c-o)) from the released acetate (1573.6 cm -1, vas(c-o)). By the on-line combination of an electrochemical flow cell with ESI-MS several product complexes could be identified. A di-μ-oxo bridged III,IV dimer [Mn2(bpmp)(μ-O) 2]2+ (m/z 335.8) can be generated at potentials below the III,III/II,III couple of the di-μ-acetato complex (0.61 V vs. ferrocene). The ligand-exchange reactions allow for three metal-centered oxidation steps to occur from II,II to III,IV in a potential range of only 0.5 V, explaining the formation of a spin-coupled III,IV dimer by photo-oxidation with [Ru[bpy) 3]3+ in previous EPR studies.",
author = "Gerriet Eilers and Camilla Zettersten and Leif Nyholm and Leif Hammarstr{\"o}m and Reiner Lomoth",
year = "2005",
month = "3",
day = "21",
doi = "10.1039/b415148h",
language = "English",
pages = "1033--1041",
journal = "Dalton Transactions",
issn = "1477-9226",
publisher = "Royal Society of Chemistry",
number = "6",

}

TY - JOUR

T1 - Ligand exchange upon oxidation of a dinuclear Mn complex-detection of structural changes by FT-IR spectroscopy and ESI-MS

AU - Eilers, Gerriet

AU - Zettersten, Camilla

AU - Nyholm, Leif

AU - Hammarström, Leif

AU - Lomoth, Reiner

PY - 2005/3/21

Y1 - 2005/3/21

N2 - The structural rearrangements triggered by oxidation of the dinuclear Mn complex [Mn2(bpmp)(μ-OAc)2]+ (bpmp = 2,6-bis[bis(2-pyridylmethyl)amino]methyl-4-methylphenol anion) in the presence of water have been studied by combinations of electrochemistry with IR spectroscopy and with electrospray ionization mass spectrometry (ESI-MS). The exchange of acetate bridges for water (D2O) derived ligands in different oxidation states could be monitored by mid-IR spectroscopy in CD 3CN-D2O mixtures following the vas(c-o) bands of bound acetate at 1594.4 cm-1 (II,II), 1592.0 cm-1 (II,III) and 1586.5 cm-1 (III,III). Substantial loss of bound acetate occurs at much lower water content (<0.5% v/v) in the III,III state than in the II,II and II,III states (≥10%). The ligand-exchange reactions do not initially reduce the overall charge of the complex but facilitate further oxidation by proton-coupled electron transfer as the water-derived ligands are increasingly deprotonated in higher oxidation states. In the IR spectra deprotonation could be followed by the formation of acetic acid (DOAc, ∼1725 cm-1, v(c-o)) from the released acetate (1573.6 cm -1, vas(c-o)). By the on-line combination of an electrochemical flow cell with ESI-MS several product complexes could be identified. A di-μ-oxo bridged III,IV dimer [Mn2(bpmp)(μ-O) 2]2+ (m/z 335.8) can be generated at potentials below the III,III/II,III couple of the di-μ-acetato complex (0.61 V vs. ferrocene). The ligand-exchange reactions allow for three metal-centered oxidation steps to occur from II,II to III,IV in a potential range of only 0.5 V, explaining the formation of a spin-coupled III,IV dimer by photo-oxidation with [Ru[bpy) 3]3+ in previous EPR studies.

AB - The structural rearrangements triggered by oxidation of the dinuclear Mn complex [Mn2(bpmp)(μ-OAc)2]+ (bpmp = 2,6-bis[bis(2-pyridylmethyl)amino]methyl-4-methylphenol anion) in the presence of water have been studied by combinations of electrochemistry with IR spectroscopy and with electrospray ionization mass spectrometry (ESI-MS). The exchange of acetate bridges for water (D2O) derived ligands in different oxidation states could be monitored by mid-IR spectroscopy in CD 3CN-D2O mixtures following the vas(c-o) bands of bound acetate at 1594.4 cm-1 (II,II), 1592.0 cm-1 (II,III) and 1586.5 cm-1 (III,III). Substantial loss of bound acetate occurs at much lower water content (<0.5% v/v) in the III,III state than in the II,II and II,III states (≥10%). The ligand-exchange reactions do not initially reduce the overall charge of the complex but facilitate further oxidation by proton-coupled electron transfer as the water-derived ligands are increasingly deprotonated in higher oxidation states. In the IR spectra deprotonation could be followed by the formation of acetic acid (DOAc, ∼1725 cm-1, v(c-o)) from the released acetate (1573.6 cm -1, vas(c-o)). By the on-line combination of an electrochemical flow cell with ESI-MS several product complexes could be identified. A di-μ-oxo bridged III,IV dimer [Mn2(bpmp)(μ-O) 2]2+ (m/z 335.8) can be generated at potentials below the III,III/II,III couple of the di-μ-acetato complex (0.61 V vs. ferrocene). The ligand-exchange reactions allow for three metal-centered oxidation steps to occur from II,II to III,IV in a potential range of only 0.5 V, explaining the formation of a spin-coupled III,IV dimer by photo-oxidation with [Ru[bpy) 3]3+ in previous EPR studies.

UR - http://www.scopus.com/inward/record.url?scp=16244387969&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=16244387969&partnerID=8YFLogxK

U2 - 10.1039/b415148h

DO - 10.1039/b415148h

M3 - Article

SP - 1033

EP - 1041

JO - Dalton Transactions

JF - Dalton Transactions

SN - 1477-9226

IS - 6

ER -