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Title: Formation kinetics of pendant arm polyamine macrocycles with copper(II)
Contributor(s): Lye, P (author)orcid ; Lawrance, GA (author); Maeder, M (author)
Publication Date: 2001
DOI: 10.1039/b102845f
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Abstract: The complexation reaction between Cu(II) and a series of cyclam analogue macrocycles with dangling primary amine groups was investigated in aqueous solution. The pH dependence of the reaction was measured between pH 0 and 5.5 covering a range of different protonation stages of the ligands. The kinetics was observed by stopped-flow measurements followed at many wavelengths. An initial second order reaction results in an intermediate which isomerises to a stable complex. The observed rate constants for the initial step varied between 1.5 × 10-2 M-1 s-1 at pH 0 and 6.3 × 105 M-1 s-1 at pH 5.3; for the secondary step the rates varied between 2 × 10-4 s-1 at pH 1 and 24 s-1 at pH 5.3. The pH dependence was successfully analysed in terms of the different reactivities for differently protonated ligands for the first step and differently protonated complexes for the second step. Ligands with unprotonated dangling primary amines react with rate constants of 106–107 M-1 s-1, the rates drop dramatically upon protonation of the arms to ca. 10–102 M-1 s-1 which are very similar to the rates of the parent cyclam ligand of equivalent protonation. The pH dependence of the secondary isomerisation reaction is explained in similar ways: protonated, dangling arms inhibit the isomerisation reaction completely.
Publication Type: Journal Article
Source of Publication: Dalton Transactions (16), p. 2376-2382
Publisher: Royal Society of Chemistry
Place of Publication: United Kingdom
ISSN: 1477-9226
Field of Research (FOR): 030207 Transition Metal Chemistry
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
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