Coordination assemblies of Coii/Niii/Mnii/Znii with 1,1′-biphenyl-2,2′-dicarboxylic acid and three positional isomeric ligands: structural diversity and properties

Abstract

Hydrothermal reactions of 1,1′-biphenyl-2,2′-dicarboxylic acid (H₂dpa) with Co(II), Ni(II) Mn(II) and Zn(II) salts, and systematically varied N-donor co-ligands (positional isomeric dipyridyl bridging ligands: 4,4′-bpt, 3,4′-bpt and 3,3′-bpt), lead to the formation of a series of supramolecular complexes, namely, [Co(dpa)(4,4′-bpt)(EtOH)(H₂O)] (1), [Ni(dpa)(4,4′-bpt)(H₂O)₂]·2.5H₂O (2), [Cu(dpa)(4,4′-bpt)(H₂O)]·2H₂O (3), [M(dpa)(3,4′-bpt)]·H₂O (M = Co for 4, Ni for 5, Mn for 6, and Zn for 7, respectively), [Zn₃(OH)₂(dpa)₂ (3,3′-bpt)₂]·2H₂O (8) (where 4,4′-bpt = 1H-3,5-bis(4-pyridyl)-1,2,4-triazole, 3,4′-bpt = 1H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole and 3,3′-bpt = 1H-3,5-bis(3-pyridyl)-1,2,4-triazole). Structural analysis reveals that dpa manages the M(II) (M = Co, Ni, Mn and Zn) ions to form 1-D chains, which are further extended via the isomeric bpt connectors in different directions, to give rise to a variety of coordination polymers of 1–8. Magnetic susceptibilities of complexes 1–6 reveal the weak antiferromagnetic or ferromagnetic exchange interactions between the adjacent metal centers. Moreover, the luminescent properties of 7–8 have been briefly investigated.