Two manganese(II) complexes based on anthracene-9-carboxylate: Syntheses,crystal structures,and magnetic properties

Abstract  To explore the influence of the anthracene ring skeleton, with a large conjugated π-system, on the structures and properties of its complexes, two Mn^II complexes with anthracene-9-carboxylate ligand were synthesized and structurally characterized: {Mn(L)₂(H₂O)₂](H₂O)}_∞ (1) and Mn₂(L)₄(phen)₂(μ-H₂O)](CH₃OH) (2) (L = anthracene-9-carboxylate and phen = 1,10-phenanthroline). Complex (1) has a one-dimensional (1D) chain structure that is further assembled to form a two-dimensional (2D) sheet, and then an overall three-dimensional (3D) network by π···π stacking and/or C–H···π interactions. Complex (2) makes a dinuclear structure by incorporating the chelating phen ligand, which is further interlinked via inter-molecular π···π stacking and C–H···π interactions to generate a higher-dimensional supramolecular network along the different crystallographic directions. The results reveal that the bulky anthracene ring skeleton in L, by virtue of intra- and/or inter-molecular π···π stacking and C–H···π interactions, plays an important role in the formation of complexes (1) and (2). The magnetic properties of (1) and (2) were further investigated. As expected, the very long inter-metallic separations result in weak magnetic coupling, with the corresponding coupling constant values of J = −10 cm⁻¹ for (1) and J = −2.46 cm⁻¹ for (2). Graphical abstract  The constructions of two new Mn^II complexes comprising 1D chain (1) and dinuclear subunit (2) structures have been successfully achieved by using a bulky anthracene-9-carboxylic acid (HL), together with incorporating the chelating 1,10-phenanthroline as a co-ligand for (2). The result reveals that the bulky anthracene ring skeleton of HL, by virtue of intra- and/or inter-molecular π···π stacking and C–H···π interactions, plays an important role in the formation of the supramolecular architectures of (1) and (2). Moreover, magnetic properties of the complexes have been investigated.