Complexation of Cu2+ by Binucleating Macrocycles Containing the N6 Donor Set |
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Authors: | Richard W. Cruse,Susan Kaderli,Walter Spieler,Andreas D. Zuberbü hler |
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Abstract: | The hexadentate ligands 1,4,7,12,15,18-hexaazacyclododecosane ([2]aneN6) and 1,4,7,14,17,20-hexaazacyclohexacosane ([26]aneN6) both form eight complexes with Cu2+, three of them being binuclear. The corresponding stability constants have been determined potentiometrically, and the electronic absorption spectra have been obtained from spectrophotometric data. Possible interactions of the Cu2+ pairs in the three binuclear complexes have, in addition, been investigated by ESR and and linear -sweep voltammetry (LSV). The binuclear complex of [22]aneN6 with one addditional OH group is exceptionally stable, ESR-silent, and the results of the LSV-experiments are characteristically different from those of the other binuclear complexes with both ligands. This indicates that [22]aneN6 forms a very stable hydroxo-bridged binuclear Cu2+ complex Cu2L(OH)3+, whereas in the case of [26]andN6 no bridged Cu2+ pair exists. |
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