2,2 -Bipyridine ligands trinuclear complexes

The complete redox series relative to reduction of the bipyridine ligands, in the binuclear and trinuclear complexes, should be constituted by eigth and twelve one-electron redox processes, respectively, since each bpy carries one redox orbital [10]. At room temperature and in non strictly aprotic conditions, chemical reactions, involving one of the members of the redox series, can take place, causing the termination of the redox series. The reduction processes for these species were therefore studied in strictly anhydrous DMF solutions at -54 C [8]. 

Once again, it is possible to extend these ideas to the formation of complexes containing progressively more metal centres. As an example, consider the ligand 7.57. This contains a total of three didentate 2,2 -bipyridine-like domains. Upon reaction with nickel(n) salts, a trinuclear triple-helical complex, [Ni3(7.57)3]6+ 7.58, is formed, in which each of the six-co-ordinate nickel(n) centres is co-ordinated to a didentate metal-binding domain from each of three ligand threads. 

The Lehn group synthesised the trinuclear copper(I) complex of the substituted 2,2 -bipyridyl/ether derivative 29 and confirmed its helical structure by X-ray diffraction (Figure 6.15). A dinuclear copper(I) complex of 30 (Figure 6.15) was also synthesised and subsequently the corresponding dimeric ethane-bridged bipyridine and phenanthroline ligands were also demonstrated to yield similar di-helicate copper(I) species. These results thus indicate that helicate formation is tolerant towards minor modification of ligand structure. ... 

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