Conformational control in a bipyridine linked pi-conjugated oligomer: cation mediated helix unfolding and refolding

A chiral pi-conjugated oligomer having alternate bipyridine and carbazole moieties connected through acetylinic bonds undergoes helical folding in chloroform-acetonitrile (40/60, v/v) as evident by fluorescence and circular dichroism changes. In the presence of transition metal cations such as Zn2+ defolding of the helical conformation occurs. Upon decomplexation of the cation with EDTA, the helical conformation is regained.