Free‐Standing Supramolecular Pyridine <i>N</i> ‐Oxide‐Silver(I) Metallogels

Abstract

Abstract Twenty‐seven pyridine N ‐oxides (PyNOs) are investigated to evaluate the gelation of their silver(I) trifluoroacetate (AgTFA) complexes across eight solvents. Gelation occurs selectively with PyNOs featuring electron‐donating groups, while those with electron‐withdrawing or mixed groups do not form gels. A combination of two different PyNOs, one with an electron‐donating group and the second with an electron‐withdrawing group, form a gel, suggesting that gel‐forming PyNO‐AgTFA can override the non‐gelling tendency of PyNOs comprising electron‐withdrawing groups. Pyridine‐AgTFA complexes lacking the N–O group fail to gel, underscoring the crucial role of the N–O functionality and its coordination with silver(I) in facilitating gelation. The resulting PyNO‐AgTFA gels demonstrate remarkable mechanical strengths, enabling the fabrication of free‐standing and load‐bearing gel shapes, such as rods and horseshoes, with sizes up to several centimeters. The analysis of 65 X‐ray crystal structures reveals that PyNO‐AgTFA complexes manifest four distinct structural motifs, even when crystallized under different solvents and ligand‐to‐metal ratios, demonstrating a strong preference for a specific set of silver(I) complexes. X‐ray crystallography and powder X‐ray diffraction studies predict gel structures without single crystals. Density functional theory calculations of recurring non‐covalent interactions in the crystal structures show interaction energies ranging from −1 to −92 kJ mol −1 .