Switching between Supramolecular Assemblies of Lipophilic Guanosine Derivatives Triggered by External Stimuli

Abstract

Depending on the experimental conditions, lipophilic guanosines (LipoGs) can undergo different self-assembly pathways based on different H-bonded motifs, e.g. the cyclic discrete G-quartet and the “infinite” tape-like G-ribbon. The switching between different supramolecular motifs have been obtained by a variety of external stimuli. After a general presentation of the LipoG self-assembly, in this mini-review we will discuss, the case of three different stimuli. A first example is represented by chemical stimuli: addition of an alkali metal ion stabilizes the G-quartet while its removal shifts the equilibrium toward the G-ribbon. In the second case, a lipoG armed with a terthiophene unit undergoes a pronounced variation of its supramolecular organisation by changing the polarity of the solvent: in chloroform the derivative assembles via H-bonding in a guanosine driven structure, while in the more polar (and H-bond competing) acetonitrile different aggregates are observed, where the terthiophene chains are - stacked in a helicoidal arrangement. Finally, a third type of stimulus is represented by light: the photocontrolled self-assembly of a modified guanosine nucleobase with a photoactive unit at C8 is obtained selecting the appropriate wavelength