Syntheses, Structures and Topology Variations of Metal Organic Frameworks Built From a Semi‐Rigid Tetracarboxylate Ligand

A flexible ether bridged tetracarboxylic ligand, 5‐((3,5‐dicarboxybenzyl)oxy)isophthalic acid ( H 4 L ) has been used to construct five metal organic frameworks under solvothermal condition. Complex 4 and 5 have been synthesized in presence of pyridine based coligands, 6′‐(pyridin‐4‐yl)‐4,2′:4′,4′′‐terpyridine ( L 1 ). The products formed under these conditions are formulated as {[(Ni) 1.5 (L)(C 5 H 5 N)(H 2 O)](3H 2 O)} n ( 1 ), {[(Co) 1.5 (L)](C 5 H 6 N)(1.5H 2 O)} n ( 2 ), {[(Ni)(L) 0.5 (H 2 O) 2.5 ](3H 2 O)} n ( 3 ), {[(Co) 2 (L)(L 1 )(DMF)(H 2 O)] (DMF)(4H 2 O)} n ( 4 ), {[(Cd) 2 (L)(L 1 )(DMF)(H 2 O)](DMF)(6H 2 O)} n ( 5 ). All of these complexes have been characterized by single‐crystal X‐ray diffraction, IR spectroscopy, thermogravimetry, elemental analysis, and powder X‐ray diffraction (PXRD) measurements. Compound 1 is one 2D layer structure, and compounds 2–5 are 3D coordination polymers (CPs)“. Interestingly, compound 4 and 5 are isostructural having 2D structure which lead to 3D by weak π⋅⋅⋅ π interaction between the two layers. Topological analysis of these complexes have been performed which reveals that 1 is (3,6)‐connected kgd net, 2 is (4,8)‐connected flu; sqc169 net, 3 is (4,4)‐connected dia diamond net while 4 and 5 have the same, (3,4)‐connected fsg net. Solid state photoluminescent studies were carried out of the complex 5 upon excitation at 290 nm and emission occurs at 453 nm which is attributed due to the ligand to metal charge transfer transition where as emission of the ligand L and L 1 observed at 380 nm and 395 nm respectively.