Coordination Assemblies of Co^II/Ni^II/ Zn^II/Cd^II with Succinic Acid and Bent Connectors: Structural Diversity and Spin-Canted Antiferromagnetism

Abstract

Four bent ligands, (i) 4,4′-abpt, (ii) 4,4′-Hbpt, (iii) 3,4′-Hbpt, and (iv) 3,3′-Hbpt, as well as H2suc (succinic acid) have been utilized to construct seven coordination polymers: [Co(suc)(4,4′-abpt)(H2O)2]·H2O (1), [M(suc)(4,4′-Hbpt)(H2O)]·2H2O (M = Co for 2, Ni for 3), [Cd(suc)(4,4′-Hbpt)2(H2O)2] (4), [Co(suc)(3,4′-Hbpt)(H2O)3]·H2O (5), [Zn(suc)(3,4′-Hbpt)] (6), and [Zn(suc)0.5(3,3′-bpt)(H2O)] (7) (4,4′-abpt = 4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole, 4,4′-Hbpt = 1H-3,5-bis(4-pyridyl)-1,2,4-triazole, 3,4'-Hbpt = 1H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole, and 3,3′-Hbpt = 1H-3,5-bis(3-pyridyl)-1,2,4-triazole). The crystal structure analysis reveals that 1–3 form similar two-dimensional (2D) layer structures, where the adjacent metal centers are connected by a syn–anti carboxylate bridge from suc ligands to furnish a succinate-metal chain, which is further interlinked by bent ligands. 4–7 form different 1D chains via suc anions, and bpt isomers display versatile coordination modes. The magnetic behavior of compounds 1–3 and 5 was studied, and it indicated the existence of interesting spin-canting behavior, where the bent ligands tilting the neighbor metal center could give further contribution to the canting effect. In addition, the luminescent properties of 4, 6, and 7 have been investigated in the solid state at room temperature.