Crystal Structures and Luminescence of Two Cadmium-Carboxylate Cluster-based Compounds with Mixed Ligands

Reactions of Cd(NO3)(2)center dot 4H(2)O with 2-quinolinecarboxylic acid (H-QLC) in the presence of 1,4-benzenedicarboxylic acid (H-2-BDC) or 1,3,5-benzenetricarboxylic acid (H-BTC) in DMF/H2O solvent afforded two compounds, namely, [Cd(QLC)(BDC)(1/2)(H2O)](n) (1) and [Cd(QLC)(BTC)(1/3)](n) (2). Both compounds are two-dimensional (2D) frameworks but feature different cadmium-carboxylate clusters as a result of the presence of the polycarboxylate ligands with different geometries and coordination preference. The dinuclear Cd-2(QLC)(2) units in 1 are bridged by the pairs of bridging water ligands to give a one-dimensional (1D) chain, which is further linked by the second ligand of BDC2- to form a 2D structure. Compound 2 is constructed from unique hexanuclear macrometallacyclic Cd-6(QLC)(6) clusters, which are linked by the surrounding BTC3- ligands to generate a 2D structure. Photoluminescence studies showed both compounds exhibit ligand-centered luminescent emissions with emission maxima at 405 and 401 nm, respectively.