Syntheses, structures and electrochemical properties of single and double helical inorganic complexes containing new polypyridine ligands

Abstract

New polypyridines [1,3-bis(2,2′:6′,2″-terpyridin-6-yl)benzene L1 and 1,3-bis[4-(4-tert-butylphenyl)-2,2′:6′,2″-terpyridin-6-yl) benzene] L2 were prepared. Their reactions with copper(II) acetate and silver(I) acetate gave [Cu2L1 2]4+, [Cu2L2 2]4+, [Ag2L1 2]2+ and [Ag2L2 2]2+ while [Ru2L2(terpy)2]4+ was obtained from [Ru(terpy)Cl3] (terpy = 2,2′:6′,2″-terpyridine) with L2. The complexes [Cu2L2 2][PF6] 4·6MeCN and [Ag2L2 2][PF6]·Me 2CO have been established by X-ray crystal analyses to have double helical structures. Electrospray mass spectrometry showed that the double helical [Cu2L2 2]4+ and [Ag2L1 2]2+ complexes and the single helical [Ru2L2(terpy)2]4+ complex are the only species present in solutions. All five complexes undergo reversible oxidations or reductions. Interestingly, the electrochemical data indicate substantial electronic coupling within the bimetallic double helical [M2L2]3+ (M = Cu or Ag, L = L1 and L2) but not the single helical [Ru2L2(terpy)2]4+ systems.