Rates of Water Exchange in 2,2′-Bipyridine and 1,10-Phenanthroline Complexes of CoII and MnII

Shravan S. Acharya, Bjorn Winther-Jensen, Leone Spiccia, C. André Ohlin

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The rates and activation parameters of water exchange at pH 3.0 have been determined using variable temperature 17O NMR spectroscopy for four CoII complexes and one MnII complex: [Co(bpy)(H2O)4]2+, [Co(bpy)2 (H2O)2]2+, [Co(phen)-(H2O)4]2+, [Co(phen)2 (H2O)2]2+, and [Mn(bpy)(H2O)4]2+ (bpy = 2,2′-bipyridyl and phen = 1,10-phenanthroline). Substitution of aquo ligands with 1,10-phenanthroline or 2,2′-bipyridyl leads to an increase in the rate of exchange in the manganese complexes, from k298 (1.8±0.1)×107s-1 for [Mn(H2O)6]2+ to (7.2±0.3)×107 s-1 for [Mn(phen)2 (H2O)2]2+, whereas the trends are more complex for the cobalt complexes. We have used the new data in conjunction with literature data for similar complexes to analyse the effect of M-OH2 distance and degree of substitution.

Original languageEnglish
Pages (from-to)751-754
Number of pages4
JournalAustralian Journal of Chemistry
Issue number6
Publication statusPublished - 2017

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