Pentacoordinate and Hexacoordinate Mn(III) Complexes of Tetradentate Schiff-Base Ligands Containing Tetracyanidoplatinate(II) Bridges and Revealing Uniaxial Magnetic Anisotropy

Crystal structures and magnetic properties of polymeric and trinuclear heterobimetallic Mn(III)···Pt(II)···Mn(III) coordination compounds, prepared from the Ba[Pt(CN)(4)] and [Mn(L4A/B)(Cl)] (1a/b) precursor complexes, are reported. The polymeric complex [{Mn(L4A)}(2){μ(4)-Pt(CN)(4)}](n) (2a), where H(2)L4A = N,N’-ethylene-bis(salicylideneiminate), comprises the {Mn(L4A)} moieties covalently connected through the [Pt(CN)(4)](2−) bridges, thus forming a square-grid polymeric structure with the hexacoordinate Mn(III) atoms. The trinuclear complex [{Mn(L4B)}(2){μ-Pt(CN)(4)}] (2b), where H(2)L4B = N,N’-benzene-bis(4-aminodiethylene-salicylideneiminate), consists of two [{Mn(L4B)} moieties, involving pentacoordinate Mn(III) atoms, bridged through the tetracyanidoplatinate (II) bridges to which they are coordinated in a trans fashion. Both complexes possess uniaxial type of magnetic anisotropy, with D (the axial parameter of zero-field splitting) = −3.7(1) in 2a and −2.2(1) cm(−1) in 2b. Furthermore, the parameters of magnetic anisotropy 2a and 2b were also thoroughly studied by theoretical complete active space self-consistent field (CASSCF) methods, which revealed that the former is much more sensitive to the ligand field strength of the axial ligands.