A Design Strategy for Single-Stranded Helicates using Pyridine-Hydrazone Ligands and PbII

The reactions of py-hz ligands (L1-L5) with Pb(CF3SO3)(2)H2O resulted in some rare examples of discrete single-stranded helical Pb-II complexes. L1 and L2 formed non-helical mononuclear complexes [PbL1(CF3SO3)(2)]CHCl3 and PbL2(CF3SO3)(2)][PbL2CF(3)SO(3)]CF3SO3CH3CN, which reflected the high coordination number and effective saturation of Pb-II by the ligands. The reaction of L3 with Pb-II resulted in a dinuclear meso-helicate [Pb(2)L3(CF3SO3)(2)Br]CF3SO3CH3CN with a stereochemically-active lone pair on Pb-II. L4 directed single-stranded helicates with Pb-II, including [Pb(2)L4(CF3SO3)(3)]CF3SO3CH3CN and [Pb(2)L4CF(3)SO(3)(CH3OH)(2)](CF3SO3)(3)2CH(3)OH2H(2)O. The acryloyl-modified py-hz ligand L5 formed helical and non-helical complexes with Pb-II, including a trinuclear Pb-II complex [Pb(3)L5(CF3SO3)(5)]CF(3)SO(3)3CH(3)CNEt(2)O. The high denticity of the long-stranded py-hz ligands L4 and L5 was essential to the formation of single-stranded helicates with Pb-II.