Characterization and properties of the copper(II/I) complexes of macrocyclic hexathiaether ligand [21]aneS6 |
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Authors: | Chandrika P. Kulatilleke |
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Affiliation: | Department of Natural Sciences, Box A0506, Baruch College, City University of New York, New York, NY 10010, USA |
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Abstract: | The copper(II/I) complexes of hexathiaether macrocyclic ligand, 1,4,8,11,15,18-hexathiacyclohenicosane ([21]aneS6), were synthesized, and characterized by electrochemical and spectroscopic techniques. Cyclic voltammetric studies indicate that Cu([21]aneS6)2+/+ forms a reversible one-electron redox couple. The electrochemical potential obtained for Cu([21]aneS6)2+/+ (Ef = 0.89 V, against SHE) was found to be the highest potential reported to date for a Cu2+/+ macrocyclic system in aqueous solution. By employing the Nernst equation, we can infer that the practical upper limit for formal potential of Cu(II/I)L systems maybe close to this high value. Stability constant data obtained for these complexes indicate that Cu([21]aneS6)+is 12 orders of magnitude greater in stability than that of Cu([21]aneS6)2+ indicating the favorable nature of this large macrocyclic ligand towards formation of Cu(I) complexes over Cu(II) complexes. Crystal structure of Cu([21]aneS6)+ ( Fig. 2) shows that four sulfurs adjacent to one another are coordinated to Cu+ ion in this complex. Bond angles and distances calculated for the crystal indicate that it is a distorted tetrahedron, a geometry commonly encountered by Cu(I) complexes. This is the first report of synthesis and characterization of a metal coordinated [21]aneS6 complex. |
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Keywords: | 1,4,8,11,15,18-Hexathiacyclohenicosane [21]aneS6 Hexathia-21-Crown-6 Copper Electrochemical potential Stability constants Crystal structure Blue copper proteins Thiaether coordination |
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