Unexpected chiroptical inversion observed for supramolecular complexes formed between an achiral polythiophene and ATP.

A series of supramolecular complexes between a water-soluble achiral polythiophene derivative (PT-1) and various nucleotides has been prepared. It was found that upon the introduction of adenosine diphosphate (ADP), adenosine triphosphate (ATP), and uridine triphosphate (UTP) into aqueous solutions of achiral PT-1, which has a random-coiled conformation, chiral supramolecular pi-stacked aggregates of PT-1 can be constructed. These complexes exhibit an unique split-type induced circular dichroism (ICD) in the pi-pi* transition region of the main chain. In particular, it was found that the Cotton effect of the chiral supramolecular PT-1/ATP aggregates reveals a dramatic inversion of chirality with a change in the concentration of ATP, which has not been previously observed in chiral macromolecular complexes. On the basis of extensive investigations performed with UV/Vis spectroscopy, CD spectroscopy, TEM, AFM, and dynamic light scattering (DLS), a possible mechanism for the formation of chiral superstructures of PT-1 and chiroptical inversion induced by changes in ATP concentration is proposed.