Solvent- and temperature-driven synthesis of three Cd(II) coordination polymers based on 3,3′-azodibenzoic acid ligand: Crystal structures and luminescent properties

Solvothermal reactions of Cd(OAc)2·2H2O with 3,3′-azodibenzoic acid (H2L) in N,N′-dimethylformamide (DMF) or DMF/MeOH at 100 °C or 120 °C gave rise to three cadmium(II) coordination polymers {[CdL(DMF)2]·0.5DMF}n (1), [CdL(DMF)(MeOH)]n (2) and {[Cd3L3(DMF)4]·0.5DMF}n (3). Complexes 1–3 were characterized by elemental analysis, IR, powder X-ray diffraction and single-crystal X-ray diffraction. In 1–3, dinuclear [Cd2L4(DMF)4] (1) or [Cd2L4(DMF)2(MeOH)2] (2) unit and trinuclear [Cd3L6(DMF)4] (3) unit acts as a four-connecting node to link its equivalent ones via sharing L ligands to form 2D layers, which are further connected through the C−H⋯π (1) or hydrogen-bonding interactions (2–3) to afford 3D networks with the 41263 topology. The network of 1 allows other one to be penetrated for the formation of twofold interpenetrating pcu net. The formation of 1–3 provided an interesting insight into solvent and temperature effects on the construction of coordination polymers under solvothermal conditions. In addition, the photoluminescent properties of 1–3 in solid state at ambient temperature were also investigated.

Three new cadmium(II) coordination polymers, showing 2D networks constructed from 4-connected dinuclear or trinuclear units via sharing four or six L ligands, have been successfully synthesized by using 3,3′-azodibenzoic acid (H2L) ligands. The effects of solvent and temperature have been discussed and the spectroscopic properties of these complexes were also studied.Figure optionsDownload as PowerPoint slideHighlights
► Reactions of Cd(OAc)2, 3,3′-azodibenzoic acid produce coordination polymers 1–3.
► The formation of the coordination polymers depends on solvent and temperature.
► Compounds 1–3 have 2D networks consisting of dinuclear and/or trinuclear Cd(II) units.
► Compounds 1–3 all display 41263 topology structures.