Interactions of Some Cationic Cobalt(III) Complexes with Anions Studied by the 59Co NMR Chemical Shifts

Abstract

The NMR peak of 59Co(III) cationic complexes shifts upfield upon interacting with anions when the interaction is mainly electrostatic; it shifts downfield when the hydrophobic interaction acts additively with the electrostatic interaction. These trends are enhanced in micellar solution systems.

NMR Spectroscopic Studies on Interactions of Tripositive Ions of Cobalt(III) and Chromium(III) Complexes in Micellar Solutions

“…The mode of the interactions of cobalt(III) complexes with amphiphilic systems is monitored by 59 Co NMR chemical shifts which are sensitive to the extent of solvation of the cobalt(III) complex ion: One of the present authors (M.I.) with co-workers has found that if cobalt(III) complex cation is present in the hydrophobic region of anionic amphiphiles the 59 Co signal tends to shift downfield relative to the “free” hydrated state . This trend is consistent with the relationship between the donor numbers of solvents and the 59 Co chemical shifts for [Co(en) 3 ] 3+ ; that is, less solvation of the cobalt(III) complex ion will make the 59 Co NMR resonance downfield shift…”

“…with co-workers has found that if cobalt(III) complex cation is present in the hydrophobic region of anionic amphiphiles the 59 Co signal tends to shift downfield relative to the "free" hydrated state. 5 This trend is consistent with the relationship between the donor numbers of solvents and the 59 Co chemical shifts for [Co-(en) 3 ] 3+ ; that is, less solvation of the cobalt(III) complex ion will make the 59 Co NMR resonance downfield shift. 4 In the present study, we deduce the location of solubilization and the extent of the interactions in micelles for [M(en) 3 ] 3+ , [M(chxn) 3 ] 3+ , and [M(phen) 3 ] 3+ , where M denotes Co or Cr.…”

“…The 59 Co NMR signal for the cobalt(III) complex cations tends to shift downfield if the hydrophobic interaction acts additively with the electrostatic interaction. 5 Thus it is possible that the chxn complex ion is present in the hydrophobic cores of the "sulfonate/sulfate micelles". Alternatively, hydrogen bonds of this complex with water molecules are weakened by ion pairing interactions, as has been reported from chemical shift changes for the probe ions, e.g., 23 Na ion by sulfonate/ sulfate micelles, 32,33 39 K ion by SO 4 2or CrO 4 2-, 34 and [ 59 Co-(en) 3 ] 3+ by I -.…”

“…Potassium dodecanoate (KDodec), sodium Ndodecanoylalaninate (NaDDA), and sodium N-octanoylalaninate (NaOA) were prepared as previously reported. 5 The 59 Co and 13 C NMR spectra were measured with a JEOL GX-270 FT NMR spectrometer operating at 64.6 and 67.9 MHz, respectively. The concentration of the cobalt(III) complex ion was always adjusted to 5 × 10 -3 mol dm -3 .…”

“…The sodium 1-alkanesulfonates (NaAlkaneSO 3 ) and 1-dodecyl sulfate (SDS) were guaranteed reagents of Tokyo Kasei Ltd and of Nacalai Chemicals for quantitative analysis, respectively. Potassium dodecanoate (KDodec), sodium N -dodecanoylalaninate (NaDDA), and sodium N -octanoylalaninate (NaOA) were prepared as previously reported . The 59 Co and 13 C NMR spectra were measured with a JEOL GX-270 FT NMR spectrometer operating at 64.6 and 67.9 MHz, respectively.…”