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Issue 17, 2013
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Equilibrium and kinetic studies on complex formation and decomposition and the movement of Cu2+metal ions within polytopic receptors

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Abstract

Potentiometric studies carried out on the interaction of two tritopic double-scorpiand receptors in which two equivalent 5-(2-aminoethyl)-2,5,8-triaza[9]-(2,6)-pyridinophane moieties are linked with 2,9-dimethylphenanthroline (L1) and 2,6-dimethylpyridine (L2) establish the formation of mono-, bi- and trinuclear Cu2+ complexes. The values of the stability constants and paramagnetic 1H NMR studies permit one to infer the most likely coordination modes of the various complexes formed. Kinetic studies on complex formation and decomposition have also been carried out. Complex formation occurs with polyphasic kinetics for both receptors, although a significant difference is found between both ligands with respect to the relative values of the rate constants for the metal coordination steps and the structural reorganizations following them. Complex decomposition occurs with two separate kinetic steps, the first one being so fast that it occurs within the stopped-flow mixing time, whereas the second one is slow enough to allow kinetic studies using a conventional spectrophotometer. As a whole, the kinetic experiments also provide information about the movement of the metal ion within the receptors. The differences observed between the different receptors can be interpreted in terms of changes in the network of hydrogen bonds formed in the different species.

Graphical abstract: Equilibrium and kinetic studies on complex formation and decomposition and the movement of Cu2+metal ions within polytopic receptors

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Publication details

The article was received on 22 Sep 2012, accepted on 28 Jan 2013 and first published on 29 Jan 2013


Article type: Paper
DOI: 10.1039/C3DT32220C
Citation: Dalton Trans., 2013,42, 6131-6141
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    Equilibrium and kinetic studies on complex formation and decomposition and the movement of Cu2+metal ions within polytopic receptors

    C. E. Castillo, J. González-García, J. M. Llinares, M. A. Máñez, H. R. Jimenez, E. García-España and M. G. Basallote, Dalton Trans., 2013, 42, 6131
    DOI: 10.1039/C3DT32220C

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