Subtle anion effects on molecular construction: “Metallocyclic dimer” vs “molecular strands”

Studies on the subtle anion effects on the self-assembly of a series of AgX with a new organic spacer, L (X− = CF3SO3−, ClO4−, BF4−; L = 1,2-bis(dimethyl-3-pyridylsilyl)ethane) were carried out. The slow diffusion of an organic solution of L into an aqueous solution of AgX affords the composition of [Ag(L)]X. The conformation of L is non-rigid, and thus the molecular construction is delicately dependent on the nature of the anions. For the CF3SO3− anion, L connects two Ag(I) ions (Ag(1)–N = 2.150(6), 2.153(6) Å; Ag(2)–N = 2.133(6), 2.144(6) Å) to form a 22-membered metallocyclic dimer [Ag2L2](CF3SO3)2. The CF3SO3− anion is placed between two distinct units, resulting in an infinite quasi-one-dimensional chain arrays via weak Ag⋯O interactions (Ag⋯O = 2.683, 2.721, 2.904, and 2.948 Å). By contrast, for the ClO4− and BF4− anions, L connects two silver(I) ions in a bridged fashion to give a single strand. Moreover, the single strands are extended in two directions with respect to each other by a 37.7° rotation and stacked alternately on the [100] direction. Such subtle effects may be ascribed to the metallophilic nature of counteranions. Thermal analyses indicate that both the metallocyclic dimer and the single strand are stable up to 250 °C in the solid state.