Synthesis, Structural Characterization, and Magnetic Properties of Two New Fe(III)Mn(III) 1D Bimetallic Compounds

Abstract

Two Fe(III)Mn(III) bimetallic compounds, [Tp*Fe (CN)₃][(Mn^IIIsalen)]·MeOH·MeCN (1) and [Tp*Fe (CN)₃][Mn^IIIsalphen]·MeOH·H₂O (2), were prepared by assembling the tricyanometalate building block (TEA)₄N [Tp*Fe(CN)₃] [Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate] and the respective Mn Schiff base precursors [salen = N,N′-ethylenebis(salicylideneiminate), salphen = N,N-bis(salicylidene)-1,2-phenylenediamine]. Both compounds exhibit a one-dimensional (1D) zigzag chain structure linked by cyanide bridges, forming a (−Fe–C≡N–Mn–N≡C−)_n motif. Magnetic studies show a gradual increase of χ_MT values in both complexes upon lowering temperature, indicating ferromagnetic coupling between the Fe^III and Mn^III metal centers with Curie–Weiss constants of +1.1 K in (1) and +1.0 K in (2). Ferromagnetic interactions are attributed to the significantly bent Mn–NC angles (148.52 and 152.99° for (1) and 154.9 and 151.3° for (2)). The formation of 1D chains in the presence of MeOH challenges earlier reports that linked chain formation to the absence of MeOH in the reaction medium. This finding highlights the highly sensitive nature of this reaction system to various factors, including the influence of solvents on intermolecular interactions, the coordinative properties and polarity of the solvent, the steric and electronic characteristics of the precursors, and specific reaction conditions, such as temperature, concentration, and molar ratios.