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.