Cu(I)‐Induced G‐Quartets: Robust Supramolecular Polymers Exhibiting Heating‐Induced Aqueous Phase Transitions Into Gel or Precipitate
Nihar Sahu, Chandrakanta Guchhait, Indrajit Mohanta, Vembanan Suriyaa, Bimalendu Adhikari
Abstract
Abstract Certain proteins and synthetic covalent polymers experience aqueous phase transitions, driving functional self‐assembly. Herein, we unveil the ability of supramolecular polymers (SPs) formed by G 4 .Cu + to undergo heating‐induced unexpected aqueous phase transitions. For the first time, guided by Cu + , guanosine (G) formed a highly stable G‐quartet (G 4 .Cu + )/G‐quadruplex as a non‐canonical DNA secondary structure with temperature tolerance, distinct from the well‐known G 4 .K + . The G 4 .Cu + self‐assembled in water through π‐π stacking, metallophilic and hydrophobic interactions, forming thermally robust SPs. This enhanced stability is attributed to the stronger coordination of Cu + to four carbonyl oxygens of G‐quartet and the presence of Cu + ‐ ‐ ‐Cu + attractive metallophilic interactions in Cu + ‐induced G‐quadruplex, exhibiting a significantly higher interaction energy than K + as determined computationally. Remarkably, the aqueous SP solution exhibited heating‐induced phase transitions—forming a hydrogel through dehydration‐driven crosslinking of SPs below cloud temperature ( T cp ) and a hydrophobic collapse‐induced solid precipitate above T cp , showcasing a lower critical solution temperature (LCST) behavior. Notably, this LCST behavior of G 4 .Cu + SP originates from biomolecular functionality rather than commonly exploited thermo‐responsive oligoethylene glycols with supramolecular assemblies. Furthermore, exploiting the redox reversibility of Cu + /Cu 2+ , we demonstrated control over the assembly and disassembly of G‐quartets/G‐quadruplex and gelation reversibly.