Chiral Hexanuclear Ferric Wheels

A new heterometallic pivalate {Fe8Cd} complex as an example of unusual "ferric wheel" molecular self-assembly

The interaction of the pivalate complexes of iron(iii), [Fe3O(Piv)6(H2O)3]·HPiv, and cadmium(ii), [Cd(Piv)2], in Et2O resulted in one more type of "ferric wheel" family complex, namely [Fe8(Piv)16{Cd(Piv)2}(μ-OH)8]·Et2O (1). The complex is an octanuclear iron(iii) wheel with a {Cd(Piv)2} moiety asymmetrically incorporated into the ring.

Formation of Tetranuclear Nickel(II) Complexes with Schiff-Bases: Crystal Structures and Magnetic Properties

The cubane-type structure is a typical representative of tetranuclear coordination compounds. In this work, two anionic Schiff-base ligands, (L1)2− and (L2)2−, each offering an O^N^O coordination pocket, ligate four NiII ions into a [Ni4O4] cubane core. The ligands are H2L1 = 2−[[(3-ethoxy-2−hydroxyphenyl) methylene]amino]benzenemethanol and H2L2 = 2−[[(5-fluoro-2−hydroxyphenyl)methylene]amino]benzenemethanol. In both compounds, [Ni4(L1)4(EtOH)4] (1) and [Ni4(L2)4(MeOH)4] (2), alkoxy oxygens of the ligands act in a bridging μ3-O binding mode. Magnetic susceptibility and magnetization data for compounds 1 and 2 are presented. The Ni–O–Ni bond angles of the cubane core determined from single crystal X-ray diffraction data play a key role for a magneto-structural correlation. Dominant intracube ferromagnetic behavior is observed, and the coupling parameters were determined for both compounds, leading to nonzero spin ground states in accordance with the broadly accepted bond angle guideline.

Iron(iii) bis(pyrazol-1-yl)acetate based decanuclear metallacycles: synthesis, structure, magnetic properties and DFT calculations

The synthesis, structural aspects, magnetic interpretation and theoretical rationalizations for a new member of the ferric wheel family, a decanuclear iron(iii) complex with the formula [Fe₁₀(bdtbpza)₁₀(μ₂-OCH₃)₂₀] (1), featuring the N,N,O tridentate bis(3,5-di-tert-butylpyrazol-1-yl)acetate ligand, are reported. The influence of the steric effect on both the core geometry and coordination mode is observed. Temperature dependent (2.0-300 K range) magnetic susceptibility studies carried out on complexes 1 established unequivocally antiferromagnetic (AF) interactions between high-spin iron(iii) centers (S = 5/2), leading to a ground state S = 0. The mechanism of AF intramolecular coupling was proved using a broken-symmetry approach within the density functional method at the B3LYP/def2-TZVP(-f)/def2-SVP level of theory.

An iron(iii)-centred ferric wheel Fe⊂{Fe6} with a siloxane-based bis-salicylidene Schiff base

A new iron(iii)-centred ferric wheel Fe⊂{Fe₆} of the formula [Fe₇(H₂L)₆(NCS)₆](ClO₄)₃·10H₂O, where H₄L = N,N'-bis(3-carboxylsalicylidene)-1,3-bis(3-aminopropyl)tetramethyldisiloxane, was synthesised and fully characterised. ⁵⁷Fe Mössbauer spectra indicate the presence of high spin (S = 5/2) Fe³⁺ cations adopting a slightly different coordination environment in agreement with the X-ray diffraction structure. There are competing antiferromagnetic exchange interactions along the rim (J₁ = -1.00 cm^-1) and the radius (J₂ = -1.46 cm^-1) of the wheel.

Hexagonal Co6 and zigzag Co4 cluster based magnetic MOFs with a pcu net for selective catalysis

Two magnetic MOFs with a pcu net, constructed by using hexagonal Co₆ rings and zigzag Co₄ clusters, respectively are reported. Furthermore, activated 1 exhibits an excellent catalytic selectivity in the allylic oxidation reaction of cyclohexene to form an α,β-unsaturated ketone.

Carboxylate free μ-oxo bridged ferric wheel with a record exchange coupling

An oxo-bridged, carboxylate free ‘ferric wheel’ was isolated with the molecular formula [FeIII8(μ-O)₄(L²⁻)₈] (1). The strength of antiferromagnetic interaction between the Fe(iii) ions is revealed by magnetic simulation (J₁ = −26.4 and J₂ = −170 cm⁻¹). The exchange value of −170 cm⁻¹ is the largest exchange value known for any homometallic or heterometallic wheels reported to date.

Hexagonal molecular "palladawheel"

A hexagonal molecular "palladawheel" consisting of six N,N'-diphenyl-2,6-pyridinedicarboxamide-Pd(II) pincer complexes held together via six Pd∙∙∙O=CAmide bonds was efficiently synthesized and crystallographically characterized. The hexameric ring possesses C3 (pseudo-S6) symmetry with up-down alternating phenyl substituents acting as interior "spokes" and exterior "propellers."