Three New Isostructural Coordination Polymers with Cd(II) Clusters as the SBU: Synthesis, Structural Characterization, and Luminescence Properties

Three new isostructural coordination polymers, {Cd1.33L(Cl)0.67(H2O)0.67}n (1), {Cd1.33L(Br)0.67(H2O)0.67}n (2), and {Cd1.33L(I)0.67(H2O)0.67}n (3), have been synthesized using a semiflexible in situ generated tetrazole ligand. All the complexes crystallize in cubic space group P4132. In complex 1, three Cd2+ ions along with two N atoms each from three tetrazole units form a trinuclear unit where each metal ion is additionally bridged by carboxylate O and μ3-Cl units. This Cd(II) cluster along with the ligand form a trigonal arrangement that extends to form a two-dimensional sheet that further undergoes extensive interpenetration to generate an overall three-dimensional coordination polymer. All complexes exhibit thermal stability up to ∼330 °C losing coordinated water molecules at ∼140 °C. Upon excitation at 340 nm, the complexes exhibit solid-state luminescence with an emission peak at ∼415 nm that shows slight red shift with broadening of the band with changing the halide anion from chloride to bromide to iodide.