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Ligand exchange upon oxidation of a dinuclear Mn complex--detection of structural changes by FT-IR spectroscopy and ESI-MS.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Eilers, Gerriet Zettersten, Camilla Nyholm, Leif Hammarström, Leif Lomoth, Reiner |
| Copyright Year | 2005 |
| Abstract | The structural rearrangements triggered by oxidation of the dinuclear Mn complex [Mn(2)(bpmp)(mu-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(3)CN-D(2)O mixtures following the v(as(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 (> or = 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, approximately 1725 cm(-1), v(C-O)) from the released acetate (1573.6 cm(-1), v(as(C-O))). By the on-line combination of an electrochemical flow cell with ESI-MS several product complexes could be identified. A di-mu-oxo bridged III,IV dimer [Mn(2)(bpmp)(mu-O)(2)](2+)(m/z 335.8) can be generated at potentials below the III,III/II,III couple of the di-mu-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. |
| File Format | PDF HTM / HTML |
| DOI | 10.1039/B415148H |
| PubMed reference number | 15739005 |
| Journal | Medline |
| Volume Number | 6 |
| Alternate Webpage(s) | http://www.rsc.org/suppdata/dt/b4/b415148h/b415148h.pdf |
| Alternate Webpage(s) | https://doi.org/10.1039/B415148H |
| Journal | Dalton transactions |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
