SYNTHESES, STRUCTURES AND ELECTROCHEMICAL PROPERTIES OF SINGLE AND DOUBLE-HELICAL INORGANIC COMPLEXES CONTAINING NEW POLYPYRIDINE LIGANDS

New polypyridines [1,3-bis(2,2':6',2 ''-terpyridin-6-yl)benzene L(1) a nd 1,3-bis[4-(4-tert-butylphenyl)-2,2':6',2 ''-terpyridin-6-yl)benzene ] L(2) were prepared; Their reactions with copper(II) acetate and silv er(I) acetate gave [Cu(2)L(2)(1)](4+), [Cu(2)L(2)(2)](4+), [Ag(2)L(2)( 1)](2+) and [Ag(2)L(2)(2)](2+) while [Ru(2)L(2)(terpy)(2)](4+) was obt ained from [Ru(terpy)Cl-3] (terpy = 2,2':6',2 ''-terpyridine) with L(2 ). The complexes [Cu(2)L(2)(2)][PF6](4) . 6MeCN and [Ag(2)L(2)(2)][PF6 ]. Me(2)CO have been established by X-ray crystal analyses to have-dou ble helical structures. Electrospray mass spectrometry showed that the double helical [Cu(2)L(2)(2)](4+) and [Ag(2)L(2)(1)](2+) complexes an d the single helical [Ru(2)L(2)(terpy)(2)](4+) complex are the only sp ecies present in solutions. All five complexes undergo reversible oxid ations or reductions. Interestingly, the electrochemical data indicate substantial electronic coupling within the bimetallic double helical [M(2)L(2)](3+) (M = Cu or Ag, L = L(1) and L(2)) but not the single he lical [Ru(2)L(2)(terpy)(2)](4+) systems.