Dynamic Chemical Devices: Generation of Reversible Extension/Contraction Molecular Motion by Ion‐Triggered Single/Double Helix Interconversion

Publisher Website
Google Scholar
Abstract
The polyheterocyclic strands 1-H and 2-H adopt a helical shape enforced by the pyridine–pyrimidine helicity codon. The crystal structure of 2-H shows the formation of stacks of dimers of right- and left-handed individual helices. Treatment of 1-H and 2-H with silver triflate results in the generation of double-helical entities 1-DH and 2-DH, containing two strands and two silver ions. NMR studies and determination of the crystal structure of 2-DH indicate that the duplex is stabilized by coordination of each Ag+ ion to two terminal bipyridine units, one from each strand, and by pronounced π–π stacking interactions between the internal heterocycles of the strands, yielding a very robust double helical structure. Reversible interconversion of the single and double helix may be achieved by addition of a cryptand capable of sequestering Ag+ and releasing it by protonation. Thus, successive addition of acid and base leads to reversible interconversion between the shorter (∼3.6 Å) single helix and the longer (∼10.3 Å) double helix, resulting in the generation of pronounced extension/contraction motion. The system 1,2-H/1,2-DH represents a dynamic chemical device undergoing ionic modulation of reversible molecular mechanical motion fueled by acid/base neutralization.

This publication has 38 references indexed in Scilit: