Construction of a unique 3D coordination polymer from assembly of Cd(NO3)2 with a new tetrakis(m-carboxyphenyl)azo calix[4]arene ligand

Reactions of 25,26,27,28-tetrahydroxy-calix[4]arene (1) with 4 equiv. of m-carboxybenzenediazonium chloride in the presence of NaOAc∙3H2O in DMF produced a new azo calix[4]arene [H4L] (2) (H4L = 5,11,17,23-tetrakis[(m-carboxyphenyl)azo]-25,26,27,28-tetrahydroxycalix[4]arene) in 96% yield. Hydrothermal reactions of Cd(NO3)2·4H2O with H4L at 90 °C under pH = 5.0–6.0 gave rise to a coordination polymer {[H3O]2[Cd7L4(DMF)4(EtOH)2(H2O)2]·5DMF·11.5EtOH·H2O}n (3). Compound 3 was characterized by elemental analysis, IR, powder X-ray diffraction, and single-crystal X-ray diffraction. Compound 3 consists of a 3D framework with an unprecedented (3346526371)(364135861) topology. The thermal properties of 2 and 3 were also investigated.