Syntheses, crystal structures and magnetic properties of five new manganese(ii) complexes: influence of the conformation of different alkyl/aryl substituted malonate ligands on the crystal packing

Abstract

Five new manganese(II)-based complexes of general formula [Mn(Rmal)(H₂O)]_n with Rmal = methylmalonate (Memal) (1), dimethylmalonate (Me₂mal) (2), diethylmalonate (Et₂mal) (3), butylmalonate (Butmal) (4) and benzylmalonate (Bzmal) (5) were synthesized and their structures characterized by single crystal X-ray diffraction. 1 and 2 are three-dimensional compounds whereas 3–5 exhibit two-dimensional networks. The structure of 1 consists of chains of μ-κO:κO bridged aquamanganese(II) ions which are interlinked through anti–anti carboxylate bridges. The structure of 2 is built by double μ-κO:κO bridged bis[aquamanganese(II)] entities which are linked to six other dimanganese(II) units through oxo- and anti–syn carboxylate bridges. These dinuclear entities also occur in 4 and 5. They are interconnected by anti–anti and anti–syn carboxylate bridges to four other units, leading to neutral layered structures. Finally, compound 3 consists of aqua-bridged chains of manganese(II) ions connected through tetrakis(monodentate) Et₂mal ligands leading to a sheet-like structure. The topological representation of the crystal structures shows the of four different nets: (10,3)-d utp (1), 6-connected crs (2), gek2 (3) and the square-grid sql topology (4–5). The magnetic properties of 1–5 were investigated in the temperature range 2.0–300 K. Overall antiferromagnetic behavior occurs in 1, 2, 4 and 5 with susceptibility maxima in the range 3.6–17.0 K. Compound 3 exhibits an overall antiferromagnetic behaviour in the high temperature range with a weak spin canting in the low temperature domain and magnetic ordering below ca. 32 K.