Multimetallic, double-stranded helical complexes derived from hexa(n-propylthio)novipyridine:: synthesis, structure and redox properties

4 ',4 ",4 '",4 ""',4 """,4 """'-Hexan(n-propylthio)-2,2 ';6 ',2 ":6 ",2 "':6 "',2 "":6 "",2 ""':6 ""',2 """:6 """,2 """':6 """',2 """"-novipyridine (L), a new nonadentate;ate ligand, reacts with cuprous tetrakis(acetonitrile) hexafluoro-phosphate in oxygen-free methanol at room temperature to yield the black, crystalline cuprous complex [L2Cu1/5][PF6](5). In the presence of air the corresponding mixed-valence complex [(L2CuCu1)-Cu-11/3][PF6](5) is obtained. Reaction with Cu-II and Co-II ions resulted in the formation of the corresponding trimetallic complexes [L2M3II][PF6](6). Molecular compositions were established from partial elemental analysis, FAB mass spectral data, and from electrochemical and electronic spectral data. [L2Cu1/5 ](5+) contains the most cuprous ions assembled in a oligopyridine complex to date and these complexes, analogous to others in this series, were assigned double-stranded helical structures. An intramolecular diastereotopic effect in the H-1 NMR spectrum of the diamagnetic pentacuprous complex showed its chiral nature and its stability in solution. Electrochemical studies of these complexes showed appreciable metal-metal interactions, and redox-induced transformations among the copper helicates were established spectroelectrochemically. (C) 1999 Elsevier Science S.A. All rights reserved.