Tuning the topologies of MnII complexes with 3-(2-pyridyl)pyrazole and carboxylate ligands by intramolecular hydrogen bonds and the geometries of pendant ligands: crystal structures and magnetic properties

Abstract

In our efforts to investigate the influence of intramolecular hydrogen bonding interactions and the geometries of pendant ligands on the structures of low-dimensional coordination architectures, two kinds of ligands have been selected: a) a chelating ligand, 3-(2-pyridyl)pyrazole (L¹), with a non-coordinated nitrogen atom as a good hydrogen bonding acceptor and b) three pendant monocarboxylato ligands with different aromatic backbones (L², L³ and L⁴) , and their Mn^II complexes, [Mn(L¹)₂(L²)₂] (1), [Mn(L¹)₂(L³)₂] (2) and [Mn₂(L¹)₂(L⁴)₄] (3), have been prepared and structurally characterized by single crystal X-ray diffraction analysis. The results show clearly that the chelating 3-(2-pyridyl)pyrazole ligand plays the dominant role in the adjustment of the modes of the monocarboxylate ligands through strong intramolecular hydrogen bonding interactions and results in the formation of low-dimensional coordination complexes. The geometry of the anthracene ring also plays a vital role in determining the topology of 3, which further affects the magnetic interactions between the metal centers.