Methanolysis and Phenolysis Routes to Fe₆, Fe₈, and Fe₁₀ Complexes and Their Magnetic Properties:  A New Type of Fe₈ Ferric Wheel

Abstract

Alcoholysis of preformed tetranuclear and hexanuclear iron(III) clusters has been employed for the synthesis of four higher-nuclearity clusters. Treatment of [Fe(4)O(2)(O(2)CMe)(7)(bpy)(2)](ClO(4)) with phenol affords the hexanuclear cluster [Fe(6)O(3)(O(2)CMe)(9)(OPh)(2)(bpy)(2)](ClO(4)) (1). Reaction of [Fe(6)O(2)(OH)(2)(O(2)CR)(10)(hep)(2)] (R = Bu(t) or Ph) with PhOH affords the new "ferric wheel" complexes [Fe(8)(OH)(4)(OPh)(8)(O(2)CR)(12)] [R = Bu(t) (2) or Ph (3)]. Complexes 2 and 3 exhibit the same structure, which is an unprecedented type for Fe(III). In contrast, treatment of [Fe(6)O(2)(OH)(2)(O(2)CBu(t))(10)(hep)(2)] with MeOH leads to the formation of [Fe(10)(OMe)(20)(O(2)CBu(t))(10)] (4), which exhibits the more common type of ferric wheel seen in analogous complexes with other carboxylate groups. Solid-state variable-temperature magnetic susceptibility measurements indicate spin-singlet ground states for complexes 2 and 4. The recently developed semiempirical method ZILSH was used to estimate the pairwise exchange parameters (J(AB)) and the average spin couplings S(A)[empty set].S(B)[empty set] between the Fe(III) centers, providing a clear depiction of the overall magnetic behavior of the molecules. All exchange interactions between adjacent Fe(III) atoms are antiferromagnetic.

{Fe6O2}-Based Assembly of a Tetradecanuclear Iron Nanocluster

“…A survey of compounds derived in this manner indicates that such compounds can eliminate weakly bound solvent molecules or ligands, giving higher nuclearity metal clusters by oligomerization of the initial metal cores [16,17,18,19]. A third, very useful synthetic path includes the use of hydrolysis or alcoholysis reactions in the presence of carboxylate groups [20,21]. In the forth synthetic strand, hydro- and solvothermal heating under higher pressure as well as a microwave irradiation has also proven useful to induce aggregation of smaller units into larger clusters, with several reported precedents [22,23].…”

Weak antiferromagnetic coupling in molecular ring is predicted correctly by density functional theory plus Hubbard U

“…3,[6][7][8] A specific type of molecular magnets, called antiferromagnetic ͑AFM͒ molecular wheels, attracted especial attention for this reason. [9][10][11][12] Unlike other types of molecular magnets, a magnetic wheel has only one single loop of the fused transition metals polyhedra. Mn 12 based wheel was first reported by Rumberger et al 13 The smallest molecule of this type is the tetranuclear manganese complex, ͓Mn 4 ͑anca͒ 4 ͑Htea͒ 2 ͑dbm͒ 2 ͔ • 2.5Et 2 O, reported by Beedle et al 14 The larger wheels include the ͓Mn 24 ͔ wheel, 15 the ͓Mn 22 ͔ wheels, 16 and the ͓Mn 84 ͔ wheel.…”

Comparison of Semiempirical ZILSH and DFT Calculations of Exchange Constants in Fe4 Butterfly Complexes

“…32,33,35,36 One goal of this work is to compare exchange constants obtained in two ways, using spin couplings properly calculated as expectation values of the local spin operator or using spin couplings appropriate for two-center spin eigenfunctions. Values for the latter case for each spin component are given by replacing positive values of 〈Ŝ A · Ŝ B 〉 UHF in Table 1a with +6.25 and negative values with -8.75.…”