Abstract

The self-assembly of polymeric networks from different Ag(I) salts and the flexible ligand 1,3-bis(4-pyridyl)propane (bpp) has been systematically investigated in order to obtain some basic information useful for the crystal engineering of coordination frames upon variation of the counterions. The salts AgNO₃, AgBF₄, AgClO₄, AgPF₆, AgAsF₆ and AgSbF₆ have been reacted in the molar ratio Ag∶bpp of 1∶2. Though in some cases we have observed the formation of mixtures, containing also minor amounts of the 1∶1 adducts [Ag(bpp)]X, the [Ag(bpp)₂]X derivatives have been obtained for all the salts, and all of the isolated crystalline products have been characterized by single-crystal X-ray analysis. Polymeric 2D and 3D networks have been observed, exhibiting four different structural motifs: [Ag(bpp)₂](NO₃) (1) contains 2D layers of square meshes that show 2-fold parallel interpenetration; compounds [Ag(bpp)₂](BF₄) (2) and [Ag(bpp)₂](ClO₄) (3) are isomorphous and contain 2-fold interpenetrated diamondoid networks; more surprisingly, compounds [Ag(bpp)₂](PF₆) (4) and [Ag(bpp)₂](AsF₆) (5) show a wafer-like structure containing, for the first time, 2-fold entangled (4,4) layers alternated to simple (4,4) layers; and finally, [Ag(bpp)₂](SbF₆) (6) contains single 2D layers of tessellated 4-membered rings. A brief analysis of the known coordination polymers based on the bpp ligand is also reported, including the structure of the novel species [Cu(NO₃)₂(bpp)]₂·2CH₂Cl₂, a molecular ring that represents the unique example showing the GG conformation for the bpp ligands.