Four coordination polymers based on flexible carboxylic acid and bis(pyridyl) mixed ligands: synthesis, structures, fluorescent and magnetic properties

Hydrothermal reactions of Zn(II), Cd(II), Co(II) or Cu(II) acetates with 2,4-DH and BPP as flexible ligands (2,4-DH = 2,4-dichlorophenoxyacetic acid, BPP = 1,3-bis(4-pyridyl)propane) afforded four new coordination polymers, [Zn(2,4-D)2(BPP)]n (1), [Cd4(2,4-D)8(BPP)4(H2O)2]n (2), [Co2(2,4-D)4(BPP)2(H2O)]n (3) and [Cu4(2,4-D)6(BPP)2(OH)2]n (4). In these complexes, the BPP ligands bridge different secondary building units, forming diverse networks based on different metal centers. Complex 1 displays a 1D chain structure with four-coordinated Zn(II) atoms connected by BPP ligands, and the resulting 1D chains are further assembled into 2D networks through aromatic π–π stacking interactions. In complexes 2 and 3, the binuclear Cd(II) or Co(II) units are bridged by the BPP ligands to generate 2D networks. Complex 4 shows a 1D double-chain structure with the tetranuclear Cu(II) units linked by BPP bridges. The fluorescence and magnetic properties of these complexes have been investigated.