Structural and magnetic characterizations of the first manganese(iii) Schiff base complexes involving hexathiocyanidoplatinate(iv) bridges

Abstract

The reactions of [Mn^III(L4a)Cl] or [Mn^III(L4b)Cl] with [Pt(SCN)₆]²⁻ resulted in the formation of a 1D polymeric complex [{Mn(L4a)}₂{μ-Pt(SCN)₆}]_n (1) and a trinuclear compound [{Mn(L4b)(H₂O)}₂{μ-Pt(SCN)₆}] (2), where L4a and L4b are tetradentate dianionic Schiff base ligands, H₂L4a = N,N′-ethylenebis(salicylimine) and H₂L4b = N,N′-3-methylbenzenebis(3-ethoxysalicylimine). In compound 1, the adjacent [Mn(L4a)]⁺ subunits are bound together through the phenolic oxygen atoms, thus forming [{Mn(L4a)}₂]²⁺ dimers with the shortest Mn⋯Mn distance of 3.2101(5) Å, while in compound 2, the intermolecular bifurcated O–H⋯O hydrogen bonds between the neighbouring molecules form [{Mn(L4b)(H₂O)}₂]²⁺ dimers, resulting in a supramolecular 1D chain structure. The Mn⋯Mn distance within the supramolecular dimer is 4.7007(9) Å, while the shortest Mn⋯Mn distance between the dimers is 9.2347(10) Å. The magnetic analyses comprising the zero-field splitting resulted in a ferromagnetic exchange interaction within the phenolato-bridged dimer in 1 (J = +1.73 cm⁻¹, D_Mn = −2.65 cm⁻¹) and the antiferromagnetic exchange interaction within the supramolecular dimer in 2 (J = −0.88 cm⁻¹, D_Mn = −3.06 cm⁻¹). The experimental findings regarding the dominant as well as negligible exchange pathways are in good agreement with the results from DFT calculations at the B3LYP/TZVP level of theory.