Construction and structural diversity of Cd-MOFs with pyrazole based flexible ligands and positional isomer of naphthalenedisulfonate

Abstract

In the present communication, we have reported the construction of a series of Cd(II)-MOFs using conformationally flexible ligand (CFL); 3,3′,5,5′-tetramethyl-4,4′-bipyrazolyl (H2BPz), flexible bent ligand (FBL); methylenebis-(3,5-dimethylpyrazole) (H2MBPz) and positional isomer of naphthalene disulfonic acid salt ligands (1,5-NDS, 2,6-NDS). By using these ligands, four new coordination polymers namely [Cd(H2MBPz)2∙1,5-NDSA]n (NDS-MOF-1), [Cd(H2BPz)∙1,5-NDSA]n (NDS-MOF-2), {[Cd(H2MBPz)2]2+∙2,6-NDSA2−}n (NDS-MOF-3) and {[Cd(H2BPz)2]2+∙2,6-NDSA2−}n (NDS-MOF-4) have been synthesized. The crystal structure analysis revealed that the employment of positional isomeric naphthalene disulfonic acid salts resulted in different architectures ranging from one dimensional chain to two dimensional grid network and further connected into a three dimensional supramolecular structure through intermolecular hydrogen bonds, π⋯π and C–H⋯π interactions. In addition, the photophysical properties and thermal stability studies for all the NDS-MOFs 1–4 were also investigated.