One-dimensional coordination polymers of Mn^II, Cu^II, and Zn^II supported by carboxylate-appended (2-pyridyl)alkylamine ligands-structure and magnetism

Abstract

Four new complexes [Mn^II(L¹OO)(H₂O)][ClO₄]·2H₂O (1), [Zn^II(L¹OO)][ClO₄]·2H₂O (2), [Cu^II(L³OO)][CF₃SO₃]·H₂O (3), and [Zn^II(L³OO)][ClO₄] (4) (L¹OO- = 3-[(2-(pyridine-2-yl)ethyl){2-(pyridine-2-yl)methyl}amino]propionate; L³OO^- = 3-[(2-(pyridine-2-yl)ethyl){(dimethylamino)ethyl}amino]propionate) have been synthesized and characterized by elemental analysis, IR, and UV/Vis spectroscopy. Structural analysis revealed that 1, 3, and 4 are one-dimensional chain-like coordination polymers. In 1 distorted octahedral MnN₃O₃ and in 3 square-pyramidal CuN₃O₂ coordination is satisfied by three nitrogen atoms and an appended carboxylate oxygen atom of the ligand, and an oxygen atom belonging to the carboxylate group of an adjacent molecule. In 4 trigonal bipyramidal ZnN₃O₂ coordination environment is provided by two nitrogen atoms and an appended carboxylate oxygen atom of the ligand in the equatorial plane, and the two axial positions are satisfied by a tertiary amine nitrogen and an oxygen atom belonging to the carboxylate group of an adjacent molecule. In 1 the Mn^II center is coordinated by an additional water molecule. In these complexes each monomeric unit is sequentially connected by syn-anti carboxylate bridges. Temperature-dependent magnetic susceptibilities for 1 and 3 are measured, revealing antiferromagnetic interactions through syn-anti carboxylate bridges between the M^II centers. Analysis of the crystal packing diagram reveals that in 1 extensive π-π stacking involving alternate pyridine rings of adjacent 1D chain exists, which eventually lead to the formation of a 2D network structure.