Cyanido-bridged {FeIIILnIII} heterobimetallic chains assembled through the [FeIII{HB(pz)3}(CN)3]− complex as metalloligand: synthesis, crystal structure and magnetic properties. Issue 26 (2nd June 2021) - Visinescu, Diana
Abstract : The first isostructural series of cyanido-bridged 3d–4f chains showing a unique zig-zag motif have been obtained by using the heteroleptic [Fe III {HB(pz)3 }(CN)3 ] − complex as a metalloligand towards the preformed [Ln III (bpdo)(NO3 )2 (H2 O)] + species. Abstract : A new series of cyanido-bridged {Fe III Ln III } heterobimetallic chains of general formula {[(NC)Fe III {HB(pz)3 }(μ-CN)2 Ln III (bpdo)(NO3 )2 (H2 O)]·CH3 CN} n [HB(pz)3 − = hydrotris(pyrazol-1-yl)borate, bpdo = 2, 2′-bipyridine- N, N ′-dioxide and Ln = Gd (1 ), Tb (2 ), Dy (3 ) and Ho (4 )], were obtained by using the low-spin [Fe{HB(pz)3 }(CN)3 ] − complex as a metalloligand towards the preformed [Ln(bdpo)(NO3 )2 (H2 O)] + species. Single-crystal X-ray diffraction shows that 1–4 are isostructural compounds that crystallize in the monoclinic P 21 / c space group. Their crystal structure consists of neutral 1D coordination polymers where the [Fe{HB(pz)3 }(CN)3 ] − fragment adopts a bis-monodentate coordination mode, through two cis -cyanido ligands, towards two [Ln(bdpo)(NO3 )2 (H2 O)] + units. The two cis -oriented cyanide bridges determine the formation of angular cyanido-bridged [Fe III Ln2 III ] trinuclear moieties that are alternatively perpendicular to each other, describing a unique zig-zag chain. Each crystallographic independent iron(iii ) ion in 1–4 is six-coordinate in a distorted octahedral surrounding, the coordination sphere being built by one tridentate HB(pz)3 − ligand and three cyanide groups, disposed in a fac -arrangement. The lanthanide(iii ) ions from 1–4 are nine-coordinate in an environment close to a distorted muffin-like geometry ( C s symmetry) and a spherical tricapped trigonal prism ( D 3h symmetry). The iron⋯lanthanide intermetallic distances through the cyanide ligands are 5.36/5.50 (1 ), 5.49/5.35 (2 ), 5.34/5.48 (3 ) and 5.33/5.47 Å (4 ). Two-dimensional supramolecular networks are built from the heterobimetallic d/f chains through weak slipped-off π–π and C–H⋯π stacking interactions. Solid-state direct-current (dc) magnetic susceptibility measurements in the temperature range 1.9–300 K for 1–4 revealed the occurrence of weak antiferromagnetic interactions in 1 [ J = −0.298 cm −1 ( α = 0), the spin Hamiltonian being defined as with S A = 1/2 and S B = 7/2] whereas the coexistence of the spin–orbit coupling of the lanthanide(iii ) [Tb III (2 ), Dy III (3 ), Ho III (4 )] and low-spin iron(iii ) ions together with the ligand field effects masked the visualization of the possible magnetic interactions in 2–4 .