Silver(I)−Thiophene π Interaction in the Assembly of Coordination Networks with the Supramolecular Synthons R−C⋮C⊃Agn (R = 2- or 3-thienyl; n = 4)†

Silver−thiophene π interactions in two bonding modes, namely, η2-(CC) and κ-(C,S), have been observed for the first time in crystalline silver(I) complexes (C4H3S-2)C⋮CAg·4AgCF3CO2 (1), 2[(C4H3S-2)C⋮CAg]·8AgCF3CO2·CH3CN (2), and (C4H3S-3)C⋮CAg·4AgCF3CO2 (4), bearing thiophene ligands with an ethynide substituent at the 2- or 3-position. Introduction of an additional betaine component in 3[(C4H3S-2)C⋮CAg]·8AgCF3CO2·Me3N+CH2CO2-·4.5H2O (3) and replacement of trifluoroacetate by pentafluoropropionate in (C4H3S-3)C⋮CAg·5AgC2F5CO2·4H2O (5) were found to interrupt these silver−thiophene π interactions and instead form an infinite π−π-stacked silver chain and a π−π-stacking-stabilized Ag8 aggregate, respectively. The establishment of a new kind of silver−ethynide supramolecular synthon, R−C⋮C⊃Agn (R = 2-, 3-thienyl; n = 4), highlights the potential of building metal−organic frameworks utilizing the π-coordination capacity of a heterocyclic ring.