pH-dependent self-assembly of divalent metals with a new ligand containing polycarboxylate: syntheses, crystal structures, luminescent and magnetic properties

Abstract

Six new coordination polymers, namely, [Cd(HL)(4,4′-bpy)(H₂O)]·H₂O (1), [Cd₃(L)₂(4,4′-bpy)₃(H₂O)]·2.5H₂O (2), [Co(HL)(4,4′-bpy)]·H₂O (3), [Co₂(L)(4,4′-bpy)_0.5(μ₃-OH)(H₂O)₂]·H₂O (4), [Zn(HL)(BIMB)]·2H₂O (5), [Zn₃(L)₂(BIMB)₂]·3H₂O (6), where H₃L = 5-(4-carboxybenzyloxy)isophthalic acid, 4,4′-bpy = 4,4′-bipyridine, BIMB = 1,4-di(1H-imidazol-1-yl)benzene, have been synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction. In complexes 1, 3 and 5, H₃L ligand is partially deprotonated in the form of HL²⁻; while in 2, 4 and 6, it is completely deprotonated due to the influence of different pH values. Complexes 1 and 5 are 2D layer structures, the hydrogen bonds between lattice-water molecules and carboxylate groups of HL²⁻ ligands extend the 2D layer into a 3D framework; while complex 3 is a 3D framework with α-Po topology. Complex 2 is a 3D fourfold interpenetrating (3,4,4)-connected net with (6³)(6²·8⁴)(6⁴·8²) topology. Complex 4 is a twofold interpenetrating (3,8)-connected net with (4³)₂(4⁶·6¹⁸·8⁴) topology. And complex 6 is a twofold interpenetrating (3,4,6)-connected net with (4·6²)(6⁴·7²)(4²·6⁶·7⁴·8·9²) topology. In addition, powder X-ray diffraction and thermogravimetric analyses for 1–6, photoluminescent properties for 1, 2, 5, 6 and magnetic properties for 3, 4 are investigated in detail.