Five new 2D and 3D coordination polymers based on two new multifunctional pyridyl–tricarboxylate ligands: hydrothermal syntheses, structural diversity, luminescent and magnetic properties

Abstract

Five coordination polymers based on pyridine–tricarboxylate ligands formulated as [Zn(HL1)] (1), [Cd₂(L1)(phen)₂(OH)]·2H₂O (2), [Co(HL1)(H₂O)₂] (3), [Co₃(L1)₂(H₂O)₈]·4(H₂O) (4) and [Mn₃(L2)₂(4,4′-bpy)₂(H₂O)₂] (5) (H₃L1 = 4-(2,4-dicarboxylphenyl) picolinic acid, H₃L2 = 5-(3′,5′-dicarboxylphenyl) nicotinic acid, phen = 1,10-phenanthroline, 4,4′-bpy = 4,4′-bipyridine) were synthesized under hydrothermal conditions. Compound 1 exhibits a 2D distorted square-grid network based on [Zn(μ-O_carboxylate)(COO)]_n chains. Compound 2 displays a 2D square-grid network based on tetranuclear [Cd₄(μ₃-OH)₂(O_carboxylate)₂(COO)₂] units in which Cd(II) ions are bridged by the mixed bridges of (μ₃-OH)₂(μ-O_carboxylate)₂. Compound 3 exhibits a 2D network based on [Co(COO)]_n chains in which Co(II) ions are bridged by a single syn–anti carboxylate bridge (μ-COO). Compound 4 features a 3D framework based on 2D layers which are further interlinked by Co(II) ions, containing [Co(COO)]_n chains which Co(II) ions are also bridged by a single syn–anti carboxylate bridge similar with that in 3. Compound 5 shows a 2D network based on trinuclear [Mn₃(COO)₆(H₂O)₂] units in which Mn(II) ions are bridged by the mixed bridges of (μ-O_carboxylate)(COO)₂. These compounds have been characterized by IR spectra, TGA and powder XRD pattern. Compounds 1 and 2 exhibit intense luminescence properties in the solid state at room temperature. Magnetic studies for compounds 3–5 demonstrated that the single carboxylate bridge in 3 and 4 transmits weak antiferromagnetic interactions between Co(II) ions while the mixed bridges of (μ-O_carboxylate)(COO)₂ transmit moderate antiferromagnetic interactions between Mn(II) ions in 5.