TY - JOUR
T1 - Observations on the structure of the ion pair formed between [Co(en)3]3+ and [Co(edta)]-
AU - Marusak, Rosemary A.
AU - Lappin, A. Graham
N1 - Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 1989
Y1 - 1989
N2 - Ion pairing phenomena in solutions involving the metal-ion complexes [Co(en)3]3+ (en = 1,2-diaminoethane) and [Co(edta)]- (edta4- = 1,2-diaminoethane-N,N,N′,N′-tetraacetate(4-)) are investigated by using nuclear magnetic resonance techniques. Specific orientation information for the [Co(edta)]- complex is obtained by high-resolution 1H NMR T1 experiments with [Cr(en)3]3+, an isostructural analogue for the cobalt(III) complex, as a paramagnetic probe. The correlation time, τc, for the [Co(edta)]-/[Co(en)3]3+ ion pair is determined to be 8.5 × 10-11 s, significantly longer than the values for the free ions. Various observed 1H([Co(edta)]-) to chromium(III) metal center distances are reported, and the metal-metal distance in the ion pair is calculated to be 3.5 A. Although the absolute distances are unrealistically short, the orientation for approach of [Cr(en)3]3+ to the [Co(edta)]- complex is obtained. In agreement with earlier results from stereoselectivity studies, the interaction of [Co(edta)]- in the ion pair is well-defined, presenting a pseudo-C3 carboxylate face to its cationic partner.
AB - Ion pairing phenomena in solutions involving the metal-ion complexes [Co(en)3]3+ (en = 1,2-diaminoethane) and [Co(edta)]- (edta4- = 1,2-diaminoethane-N,N,N′,N′-tetraacetate(4-)) are investigated by using nuclear magnetic resonance techniques. Specific orientation information for the [Co(edta)]- complex is obtained by high-resolution 1H NMR T1 experiments with [Cr(en)3]3+, an isostructural analogue for the cobalt(III) complex, as a paramagnetic probe. The correlation time, τc, for the [Co(edta)]-/[Co(en)3]3+ ion pair is determined to be 8.5 × 10-11 s, significantly longer than the values for the free ions. Various observed 1H([Co(edta)]-) to chromium(III) metal center distances are reported, and the metal-metal distance in the ion pair is calculated to be 3.5 A. Although the absolute distances are unrealistically short, the orientation for approach of [Cr(en)3]3+ to the [Co(edta)]- complex is obtained. In agreement with earlier results from stereoselectivity studies, the interaction of [Co(edta)]- in the ion pair is well-defined, presenting a pseudo-C3 carboxylate face to its cationic partner.
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U2 - 10.1021/j100355a055
DO - 10.1021/j100355a055
M3 - Article
AN - SCOPUS:0000353945
SN - 0022-3654
VL - 93
SP - 6856
EP - 6859
JO - Journal of physical chemistry
JF - Journal of physical chemistry
IS - 18
ER -