Cluster-based Cd(II) coordination polymers: Step-wise synthesis, structure, and luminescence

Two new Cd(II) coordination polymers based on a flexible ligand 5-(bis(4- carboxybenzyl)amino)isophthalic acid (H4L) namely {[Cd2(L)(NMP)2(H2O)2]·H2O}n (1) and{[Cd4(L)2(NMP)2(H2O)]∙2NMP}n (2) (NMP=N-methyl-2-pyrrolidone) have been prepared under hydrothermal conditions. Structural analyses revealed that 1 and 2 all exhibit three-dimensional network structures. Compound 1 shows 4-connect crb topology with [Cd2(CO2)4] as secondary building unit, while compound 2 can be regarded as a new 4,4,8-connect with a {411.615.82}{45.6}{46} topology with tetranuclear [Cd4(CO2)8]. By step-wise synthesis, tetranuclear cluster-based {[Cd4(L)2(NMP)2(H2O)]∙2NMP}n (2) can be synthesized successfully by using compound 1. The powder X-ray diffraction, the thermal stabilities, and solid-state luminescence properties of compounds 1–2 have also been investigated.