Cooperative Au(I)···Au(I) Interactions and Hydrogen Bonding as Origin of a Luminescent Adeninate Hydrogel Formed by Ultrathin Molecular Nanowires

Two water-soluble [Au­(⁹N-adeninate)­(PR₃)] complexes (PR₃ = PMe₃ (1); PTA (3)) were synthesized by the coordination of the respective cationic [Au­(PR₃)]⁺ fragment to the ⁹N position of the adeninate anion. Both complexes crystallize as dimers by aurophilic contacts of 3.2081(6) Å in 1 and 3.0942(7) and 3.0969(7) Å in 3, but different packings are observed due to the crystallizing solvent choice and the nature of the ancillary phosphine ligand. At this regard, different supramolecular behavior is observed in water, ranges from the formation of ultrathin nanowires of 5.3 ± 1.9 nm of diameter and up to 1.5 μm in length and leads to a blue-luminescent hydrogel for 1, to the single-crystallization of 3. Parallel computational studies carried out show that aurophilicity and N–H···N or O–H···N hydrogen bonding are comparable in strength, suggesting a competition between all types of weak forces in the final observed macroscopic properties.