Homometallic FeIII4 and Heterometallic {FeIII4LnIII2} (Ln = Dy, Tb) Complexes – Syntheses, Structures, and Magnetic Properties

Abstract

AbstractThe sequential reaction of the multisite coordination ligand 2‐methoxy‐6‐{[2‐(2‐hydroxyethylamino)ethylimino]methyl}phenol (LH2) with Fe(ClO4)2·4H2O or a combination of Fe(ClO4)2·4H2O and Ln(NO3)3·5H2O [DyIII and TbIII] in the presence of tetramethylammonium hydroxide and pivalic acid (pivH) under ambient conditions afforded a homometallic tetranuclear FeIII complex and heterometallic hexanuclear FeIII/LnIII complexes, namely, [Fe4(μ3‐O)2(L)4]·3CH3CN·2CH3OH (1), [Fe4Dy2(μ3‐O)2(L)2(O2CCMe3)10(MeOH)]·2CH3CN (2), and [Fe4Tb2(μ3‐O)2(L)2(O2CCMe3)10(HO2CCMe3)]·H2O (3). Compounds 1–3 crystallize in the monoclinic system in space group P21/n (Z = 4). The homometallic tetranuclear derivative 1 possesses three contiguous four‐membered Fe2O2 rings in a ladderlike configuration. Each of the iron centers is hexacoordinate (2N, 4O) in a distorted octahedral geometry. On the other hand, 2 and 3 contain two symmetrically related Fe2Ln units that are joined to each other through oxygen atoms from the ethoxide side arms of the ligand L2–; the two lanthanide ions are located at the opposite ends of the hexanuclear core. In 2 and 3, the lanthanide centers are eight‐ (distorted trigonal dodecahedron) and nine‐coordinate (distorted monocapped square antiprism), respectively, and the iron centers are hexacoordinate (distorted octahedral). Magnetic studies on 2 and 3 reveal the presence of weak antiferromagnetic coupling between the FeIII and LnIII ions.