Low-Dimensional 3d–4f Complexes Assembled by Low-Spin [FeIII(phen)(CN)4]− Anions

• Published in: Inorganic chemistry 2013-02, Vol.52 (3), p.1525-1537
• Main Authors: Visinescu, Diana, Toma, Luminita Marilena, Fabelo, Oscar, Ruiz-Pérez, Catalina, Lloret, Francesc, Julve, Miguel
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic302278q

The synthesis, crystal structure, and magnetic properties of four new mixed 3d–4f complexes with formulas [{FeIII(phen)(CN)4}4Gd2 III(bpym)(NO3)2(H2O)4]·2CH3CN·2H2O} n (1), [{FeIII(phen)(CN)4}4Tb2 III(bpym)(H2O)8]·(NO3)2·2CH3CN} n (2), [{FeIII(phen)(CN)4}4SmIII(bpym)(NO3)2(H2O)5]·2CH3CN} n (3), and [{FeIII(phen)(CN)4}2Pr2 III(bpym)(NO3)4(H2O)2] n (4) (phen = 1,10-phenanthroline and bpym = 2,2′-bipyrimidine) are discussed here. Compounds 1–3 are isomorphous and their structure consists of neutral ladder-like motifs where the rungs are made up by bpym-bridged dilanthanide(III) cations and the rods are defined by [Fe(phen)(CN)4]− units adopting a bis-monodentate coordination mode through two of its four cyanide ligands. The electroneutrality in this family is achieved by either a chelating [at the Gd(III) (1) and Sm(III) (3)] or free [at the Tb(III) (2)] nitrate group and a peripheral [Fe(phen)(CN)4]− entity, which act as a monodentate ligand across one of its four cyanide groups toward the rare-earth cation (1–3). Compound 4 exhibits a neutral two-dimensional structure where (μ-bpym)bis[diaquadi(nitrato-κ2-O,O′)praseodymium(III)] fragments are interlinked through [Fe(phen)(CN)4]− units adopting a tris-monodentate coordination mode across three of its four cyanide groups. Each iron(III) ion in 1–4 is six-coordinate with two nitrogen atoms from a chelating phen and four cyanide-carbon atoms building a somewhat distorted octahedral environment. The trivalent rare-earth cations are 9- (1–3) and 10-coordinate (4) having in common two nitrogen atoms from a bidentate bpym and three (1–3)/two (4) cyanide nitrogens, the coordination environment being completed by chelating nitrate (1, 3, 4) and water molecules (1–4). Magnetic susceptibility measurements in the 1.9–300 K temperature range show the occurrence of antiferromagnetic interactions in 1 through both the single cyanide- and the bis-bidentate bpym ligands. A weak ferromagnetic interaction is observed for 3 whereas very weak, if any, magnetic interactions would occur in 2 and 4, with the spin–orbit coupling of the low-spin iron(III) ion and the ligand field effects of the Tb(III) (2) and Pr(III) (4) masking their visualization.