Supramolecular Assembly of Metal-Organic Tubes Constructed from the Ditopic Heteroscorpionate Ligand (4-NH2C6H4)CHpz2 (pz = Pyrazol-1-yl) and Silver(I)

The possibility of constructing tubular metal-organic structures with aid of weak hydrogen-bonding interactions between suitably designed metallacycles was explored. For this purpose, the new heteroditopic ligand (4-NH2C6H4)CHpz(2) (L1) was prepared in good (75%) yield by a one-pot procedure starting from commercial 4-acetamidobenzaldehyde. The equimolar reactions between L1 and various silver(I) salts gave the intended 1:1 complexes in which the metallacycles were assembled into tubes. However, the exact nature of the assemblies (including their solvate compositions) varied depending on anion, solvent, and concentration of the original crystallization solution. For the trifluoromethanesulfonate anion, a hexameric structure was observed, whereas cyclic dimers were obtained for other anions. In the case of PF6-, an unusual, opened-cycle structure with the composition [(L1)Ag(-L1)Ag(CH3CN)(2)](2+) was also identified crystallographically. The capacity for desolvated tubular structures to be used for gas adsorption was also investigated.