Cadmium–Furandicarboxylate Coordination Polymers Prepared with Different Types of Pyridyl Linkers: Synthesis, Divergent Dimensionalities, and Luminescence Study

Five new metal–organic frameworks (MOFs) have been synthesized by using cadmium ion and 2,5-furandicarboxylic acid in presence of a variety of bridging amine ligands, [Cd(fdc)(2,2′-bpy)(H2O)]n (1), {[Cd(fdc)(pyz)(H2O)2][Cd(fdc)](H2O)2]·H2O}n (2), {[Cd(fdc)(4,4′-bpy)(H2O)2]·EtOH}n (3), [Cd(fdc)(1,2-bpe)(H2O)]n (4), and [{Cd2(fdc)2(H2O)4}·(1,2-bpe)]n (5), where fdc = 2,5-furandicarboxylic acid, 2,2′-bpy = 2,2′-bipyridyl, pyz = pyrazine, 4,4′-bpy = 4,4′-bipyridyl, 1,2-bpe = 1,2-di(4-pyridyl)ethylene. All the compounds were characterized by single-crystal X-ray analysis and show diversities in their structures. Compound 1 shows linear topology propagating along the crystallographic b-axis. Compound 2 shows supramolecular structure, where two types of 1D double chains (ladder type) are present. These chains propagate along the crystallographic a-axis and are tightly held with each other by strong hydrogen bonds. Compound 3 reveals a 1D + 1D → 2D polycatenated MOF, where four cadmium centers form a perfect square and these squares are further linked by the carboxylate ligand, forming a 1D tube. These tubes are interpenetrated with each other forming a polycatenated 3D MOF. Compound 4 also possesses a polycatenated MOF, but 1D sheets are polycatenated with each other forming the 1D + 1D → 3D MOF. Compound 5 is a 2D-based supramolecular 3D MOF, where 1,2-bpe ligands are entrapped within the layer of the 2D by strong hydrogen bonds and π···π interaction. Luminescence of all the compounds has been investigated.