Construction of highly water-stable fluorinated 2D coordination polymers with various N, N’-donors: Syntheses, crystal structures and photoluminescence properties

Abstract

Four new 2D coordination polymers (CPs) of Cd(II), [Cd(tfbdc)(bpy)(H2O)2]n (1) [Cd(tfbdc)(bpe)(H2O)2]n (2), [Cd(tfbdc)(4bpdb)(H2O)2]n (3), and [Cd(tfbdc)(3bpdb)(H2O)2]n (4) (where, tfbdc ​= ​2,3,5,6-tetrafluoro-1,4-benzenedicarboxylate, bpy ​= ​4,4’-bipyridine, bpe ​= ​1,2-bis(4-pyridyl)ethylene, 4bpdb ​= ​1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene), and 3bpdb ​= ​1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene) were successfully synthesized by room temperature self-assembly of Cd(II), tfbdc2− and the N, N’-bipyridine linkers. All four CPs were thoroughly characterized by single-crystal X-ray diffraction and other physicochemical studies. Structural analysis revealed that CPs 1–4 feature a 2D network structure which is further extended to 3D supramolecular framework via intermolecular (O–H⋯O) hydrogen bonding interactions between the hydrogens of the coordinated water molecule and the free carboxylate oxygen of tfbdc2− dianion. Further, the use of various ancillary bipyridine linkers has resulted in the 2D networks 1–4 with different pore sizes. Interestingly, 1–4 exhibit water stability owing to the presence of fluorinated aromatic dicarboxylate ligand and also, photoluminescence emission attributed to intra-ligand and/or ligand-to-ligand charge transfer transitions.