Design of 3d–4f molecular squares through the [Fe{(HB(pz)3)}(CN)3]− metalloligand. Issue 17 (18th April 2018)

• Record Type: Journal Article
• Authors: Alexandru, Maria-Gabriela; Visinescu, Diana; Shova, Sergiu; Oliveira, Willian X. C.; Lloret, Francesc; Julve, Miguel
• Is Part Of: Dalton transactions. Volume 47:Issue 17(2018)
• Page Start: 6005
• Page End: 6017
• Publication Date: 2018-04-18
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c8dt00895g
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : A new series of cyanido-bridged {FeIII2LnIII2} heterobimetallic molecular squares [Ln = La (1 ), Gd (2 ), Tb (3 ) and Dy (4 )] has been prepared and magneto-structurally investigated. Abstract : A new series of {FeIII2LnIII2} heterobimetallic squares of general formula [Fe III {HB(pz)3 }(CN)(μ-CN)2 Ln(pyim) x (NO3 )2 (H2 O) y ]2 · z H2 O [Ln = La (1 ), Gd (2 ), Tb (3 ) and Dy (4 ); {HB(pz)3 } − = hydrotris(pyrazolyl)borate and pyim = 2-(1 H -imidazol-2-yl)pyridine; x = 2, y = 0 (1 ), x = y = 1 (2–4 ) and z = 10 (1 ), 6 (2 ), 2.76 (3 ), 4 (4 )] were synthesized by reacting the low-spin [Fe III {HB(pz)3 }(CN)3 ] − complex anion with the preformed [Ln III (pyim) x (NO3 )2 (H2 O) y ] + complex cation [formed in situ by mixing the lanthanide(iii ) salt and the pyim ligand]. Single-crystal X-ray diffraction shows that1–4 crystallize in the P 1̄ triclinic space group, 2–4 being isomorphous. In all cases, the structure comprises neutral cyanido-bridged {FeIII2LnIII2} molecular squares in which two [Fe III {HB(pz)3 }(CN)3 ] − units act as bis-monodentate ligands towards two [Ln III (pyim) x (NO3 )2 (H2 O) y ] + moieties through two of the three cyanide groups. The iron(iii ) and lanthanide(iii ) cations regularly alternate in the corners of the square and the edges are defined by the cyanide bridges. Each iron(iii ) ion in1–4 is six-coordinate in a distorted octahedral surrounding with a tridentate tris(pyrazolyl)borate ligand and three cyanide groups in an approximately C 3v symmetry. The lanthanum(iii ) ion in1 is ten-coordinate in a rare distorted sphenocorona environment, while the lanthanide(iii ) ions in2–4 are all nine-coordinate with a muffin-like geometry. The values of the Fe III ⋯Ln III distances across the cyanide bridges are 5.579(1) and 5.687(1) Å (1 ), 5.4695(20) and 5.4781(29) Å (2 ), 5.4550(12) and 5.4464(14) Å (3 ), 5.4463(10) and 5.4478(12) Å (4 ). The tetranuclear units in1–4 are further interconnected through hydrogen bonds, π–π stacking and very weak C–H⋯π type interactions leading to supramolecular three-dimensional networks with different topologies. Solid-state direct-current magnetic susceptibility analyses in the temperature range 1.9–300 K reveal the occurrence of weak intra- and intermolecular antiferromagnetic interactions in1 [ J FeFe′ = −2.32(3) cm −1, g Fe = 2.198(4), θ = −0.650(7) K and χ TIP = 266(5) × 10 −6 cm 3 mol −1, the Hamiltonian being defined as H = − J FeFe′ S Fe S Fe′ + gβH ( S Fe + S Fe′ )] and2 [ J FeFe′ = −2.06(3) cm −1, J FeGd = −0.210(4) cm −1, g Fe = 2.23(1), g Gd = 2.0 (fixed), θ = −0.450(5) K and χ TIP = 280(5) × 10 −6 cm 3 mol −1 ]. The coexistence of the spin–orbit coupling of the low-spin iron(iii ) and lanthanide(iii ) ions [Tb III (3 ) and Dy III (4 )], together with the ligand field effects, masked the visualization of the possible magnetic interactions in3 and4 . The small antiferromagnetic couplings in1 and2 are in line with previously reported weak antiferromagnetic interactions for these couples of ions through single cyanide bridges.