Three-Dimensional Cd(II) Coordination Polymers Based on Semirigid Bis(Methylbenzimidazole) and Aromatic Polycarboxylates: Syntheses, Topological Structures and Photo luminescent Properties

To systematically explore the influence of aromatic polycarboxylate coligands on building high dimensional Cd(II)-bmb (1,4-bis(2-methylbenzimidazol-1-ylmethyl) benzene) coordination polymers, we synthesized six coordination polymers, namely {[Cd(bmb)(o-phda)]center dot H2O}(n) (I), [Cd(bmb)(0.5)(m-phda)](n) (2), [Cd(bmb)(p-phda)](n) (3), [Cd(bmb)(0.5)(oba)](n) (4), [Cd(bmb)-(bpdc)](n) (5), [Cd-2(bmb)(bta)(mta)(0.5)](n) (6), (H(2)phda = phenylenediacetic acid, H(2)oba =4,4'-oxybis(benzoic acid), H(2)bpdc = biphenyl-4,4'-dica.rboxylic acid, H(3)bta =1,2,4-benzenetricarboxylic acid, and H(2)mta = 2-(methoxycabonyl)terephthalic acid) by varying aromatic polycarboxylate coligands. Structural analyses reveal that polymers 1-6 display diverse 3D frameworks and topologies, in which all of the N-donor ligands bmb exhibit transconformation but With different N-donor center dot center dot center dot N-C-sp3 center dot center dot center dot C-sp3 torsion angles Polymer 1 shows a 3-fold interpenetrating dia array with a 4-connected 6(6) topology Polymer 2 features a (3,4) connected piller-layered structure with (6(3))(1) (6(5).8)-ins topology. Polymer 3 is a 4-connected framework with 6(6)-dia topology and two types of meso-helical chains. Polymer 4 possesses a 2-fold interpenetrating 6-connected framework with (4(12).6(3))-pcu topology. The structure of polymer 5 is a 4-connected 5-fold interpenetrating architecture with 6(6)-dia topology. Interestingly in 6, part of bta(3-) anions are converted into a new ligand mta(2-) via in situ esterification reaction under solvothermal conditions. As a result, polymer 6 exhibits scare mixed-ligands framework with two O-donor and one N-donor ligands based on tetranuclear Cd(II) clusters. It is an 8-connected (3(6).4(18).5(3).6)-hex topology.. A systematically a structural comparison of these polymers indicates that the coordination modes of aromatic polycarboxylates along with the structural characteristics of the semirigid N-donor ligand bmb simultaneously play an important role in constructing the high-dimensional frameworks Moreover, polymers 1-6 indicate high thermal stabilities and different photoluminescence behaviors in the solid state