True diffusion current of substrate ions as the rate-controlling factor of surface film growth

A pyrazolate-supported Fe(3)(mu(3)-O) core: structural, spectroscopic, electrochemical, and magnetic study

A comparison is made between the structural, spectroscopic, electrochemical, and magnetic properties of pyrazolate versus carboxylate complexes [Fe3(mu3(mu3O)(mu-LL)6Cl3]2- containing the Fe3(mu3-O)-motif. While the Fe3(mu3-O)-cores are structurally indistinguishable in the two types of complexes, their magnetic properties deviate from the expected values as a result of a through-pyrazole contribution to the overall antiferromagnetic exchange with J1/hc = -80.1 cm(-1) and J2/hc = -72.4 cm(-1), or J1/hc = 70.6 cm(-1) and J2/hc = -80.8 cm(-1), (Hex = -J1(S1S2 + S2S3) - J2S1S3). The magnetic properties of the pyrazolate complexes are further tuned by an antisymmetric exchange interaction term.

An Octanuclear Complex Containing the {Fe3O}7+ Metal Core: Structural, Magnetic, Mössbauer, and Electron Paramagnetic Resonance Studies

A new asymmetrically coordinated bis-trinuclear iron(III) cluster containing a [Fe(3)O](7+) core has been synthesized and structurally, magnetically, and spectroscopically characterized. [Fe(6)Na(2)O(2)(O(2)CPh)(10)(pic)(4)(EtOH)(4)(H(2)O)(2)](ClO(4))(2).2EpsilontOH (1.2EpsilontOH) crystallizes in the P space group and consists of two symmetry-related {Fe(3)O](7+) subunits linked by two Na(+) cations. Inside each [Fe(3)O](7+) subunit, the iron(III) ions are antiferromagnetically coupled, and their magnetic exchange is best described by an isosceles triangle model with two equal (J) and one different (J ') coupling constants. On the basis of the H = -2SigmaJ(ij)S(i)S(j) spin Hamiltonian formalism, the two best fits to the data yield solutions J = -27.4 cm(-1), J ' = -20.9 cm(-1) and J = -22.7 cm(-1), J ' = -31.6 cm(-1). The ground state of the cluster is S = (1)/(2). X-band electron paramagnetic resonance (EPR) spectroscopy at liquid-helium temperature reveals a signal comprising a sharp peak at g approximately 2 and a broad tail at higher magnetic fields consistent with the S = (1)/(2) character of the ground state. Variable-temperature zero-field and magnetically perturbed Mössbauer spectra at liquid-helium temperatures are consistent with three antiferromagnetically coupled high-spin ferric ions in agreement with the magnetic susceptibility and EPR results. The EPR and Mössbauer spectra are interpreted by assuming the presence of an antisymmetric exchange interaction with |d| approximately 2-4 cm(-1) and a distribution of exchange constants J(ij).