Self-assembly of silver(i) coordination polymers with novel layered open network structures based on a flexible double betaine ligand

Abstract

Three coordination polymers, [Ag4(L1)2(NO3)4]·H2O (1), [Ag(L1)](BF4)·2H2O (2) and [Ag2(L1)(H2O)](ClO4)2 (3), were obtained from self-assembly of AgX (X = NO3−, BF4−, or ClO4−) with a new flexible double betaine L1 (L1 = 1,3-bis(pyridinio-4-carboxylato)propane). Single crystal X-ray diffraction studies for complexes 1–3 reveal layered open network structures containing novel cavities and channels. Complex 1 consists of an unprecedented rhombic tetrameric Ag4O2 subunit, in which a μ3-η1 coordination mode of the carboxylate group is found for the first time among silver(I) carboxylates. Complex 2 is constructed from a bis(carboxylate-O,O′)-bridged centrosymmetric dimeric subunit, in which the coordination sphere of each silver(I) atom is completed by a monodentate carboxylate group at each axial site. In complex 3, the [Ag2(carboxylate-O,O′)2] dimeric subunits are extended into a polymeric chain through the linkage of each metal centre to carboxylate groups of an adjacent dimer, and such infinite chains are extended into a plane wave-like layer structure by the cross-linkage of the molecular skeletons of the flexible double betaine ligands.