Six novel Zn(II)/Cd(II) coordination polymers based on a rigid tridentate imidazolyl terpyridine ligand fine-tuned by different carboxylates: Syntheses, structural diversities and luminescence properties

Six novel coordination polymers (CPs) based on a rigid tridentate ligand, 4 & PRIME;-(4-(imidazol-1-yl)phenyl)-4,2 & PRIME;:6 & PRIME;,4 & PRIME;'-terpyridine (imphtpy), namely {[Zn2(imphtpy)2(p-bdc)2].(H2O)}n (1), [Zn(imphtpy)(m-bdc)]n (2), {[Zn (imphtpy)(qda)1.5].(H2O)}n (3), [Cd2(imphtpy)2(m-bdc)2]n (4), [Cd(imphtpy)(abtc)0.5]n (5) and [Cd(imphtpy) (qda)]n (6), (p-H2bdc = 1,4-benzenedicarboxylic acid, m-H2bdc = 1,3-benzenedicarboxylic acid, H2qda = hy-droquinone-o,o'-diacetic acid and H4abtc = 3,3 & PRIME;,5,5 & PRIME;-azobenzenetetracarboxylic acid), have been solvothermally synthesized and characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction (PXRD), ther-mogravimetric (TG) analysis and single-crystal X-ray diffraction. Complex 1 displays a pseudo four-fold inter-penetration of dia network in a [2 + 2] mode. Complex 2 exhibits a 2D-* 2D polycatenane of two-fold interpenetrated network with the sql topology. Complex 3 shows a interdigitated 2D layer with the sql topol-ogy, which is further extended into a 3D supramolecular framework through 7L-7L interactions and hydrogen bonds. Complex 4 features a two-fold interpenetrated (4,4)-connected 3D + 3D-* 3D framework with the bbf topology. Complex 5 reveals a 2D network constructed by binuclear Cd2(CO2)4 secondary building unit (SBU) with the sql topology which is further packed into a 3D supramolecular framework through 7L-7L interactions. Complex 6 is a 3D network constructed by binuclear Cd2(CO2)2O2 SBU with the uninodal 6-c pcu topology. These results indicate that the versatile coordination networks of imphtpy and various polycarboxylate ligands play crucial roles in modulating the structural topologies of coordination networks. In addtion, photo-luminescence properties have been explored for complexes 1-6 in the solid state at room temperature, which are derived from metal perturbed intraligand charge transfer (ICT) or ligand-to-ligand charge transfer.