Hydrothermal synthesis, crystal structures and photoluminescence of a 2D cadmium(II) coordination polymer based on in situ synthesized tetrazole derivative ligand

Hydrothermal reaction of methyl 4-(cyanomethoxy)benzoate, Cd(NO3)2·4H2O and NaN3 yielded a new 2D Cd(II) coordination polymer, {[Cd3(N3)2(mtzb)4(H2O)2]·(H2O)2.5}n 1 (Hmtzb = methyl 4-(1H-tetrazol-5-ylmethoxy)benzoate), which was characterized by single-crystal X-ray diffraction. The in situ [2 + 3] cycloaddition reaction of nitrile and azide in presence of Cd(II) salt afforded a new tetrazolate-based mtzbˉ ligand. In polymer 1, The cross-linkage of the mtzbˉ ligands and Cd(II) atoms forms a 2D layer network, and the mtzbˉ ligand displays two distinct μ3-bridging coordination modes, μ3-κN1:κN2:κN3 and μ3-κN1:κN2:κN4. Photoluminescent analyses revealed that 1 exhibits a strong blue emission with a fluorescent lifetime of 3.22 ns. The relevant density of states (DOS) calculation results showed that the photoluminescence mainly originates from ligand-centered charge transition.