Substituent-Guided Cluster Nuclearity for Tetranuclear Iron(III) Compounds with Flat {Fe(μ-O)} Butterfly Core.

The tetranuclear iron(III) compounds [Fe(μ-O)(μ-L)] (-) were obtained by reaction of FeCl with the shortened salen-type NO tetradentate Schiff bases -(salicylidene)--Z-phenylmethanediamine HL (Z = NO, Cl and OMe, respectively), where the one-carbon bridge between the two iminic nitrogen donor atoms guide preferentially to the formation of oligonuclear species, and the position of the substituent Z on the central phenyl ring selectively drives towards Fe bis-oxido clusters. All compounds show a flat almost-symmetric butterfly-like conformation of the {Fe(μ-O)} core, surrounded by the four Schiff base ligands, as depicted by both the X-ray molecular structures of and and the optimized geometries of all derivatives as obtained by UM06/6-311G(d) DFT calculations. The strength of the antiferromagnetic exchange coupling constants between the iron(III) ions varies among the three derivatives, despite their magnetic cores remain structurally almost unvaried, as well as the coordination of the metal ions, with a distorted octahedral environment for the two-body iron ions, Fe, and a pentacoordination with trigonal bipyramidal geometry for the two-wing iron ions, Fe.

Selective Formation, Reactivity, Redox and Magnetic Properties of Mn and Fe Dinuclear Complexes with Shortened Salen-Type Schiff Base Ligands.

The reactivity of the shortened salen-type ligands Hsalmp, Hsalmen and Hsal(-X)ben with variable -substituent on the central aromatic ring (X = Bu, Me, H, F, Cl, CF, NO) towards the trivalent metal ions manganese(III) and iron(III) is presented. The selective formation of the dinuclear complexes [M(μ-salmp)], M = Mn (), Fe (), [M(μ-salmen)(μ-OR))], R = Et, Me, H and M = Mn (-) or Fe (-), and (M(μ-sal[-X]ben)(μ-OMe)), X = Bu, Me, H, F, Cl, CF, NO and M = Mn (-) or Fe (-), could be identified by reaction of the Schiff bases with metal salts and the base NEt, and their characterization through elemental analysis, infrared spectroscopy, mass spectrometry and single-crystal X-ray diffraction of ·2AcOEt, ·2CHCN and ·2DMF was performed. In the case of iron(III) and Hsalmp, when using NaOH as a base instead of NEt, the dinuclear complexes [Fe(μ-salmp)(μ-OR)(salim)], R = Me, H (,) could be isolated and spectroscopically characterized, including the crystal structure of ·1.

Progressive approach to eruption at Campi Flegrei caldera in southern Italy.

Unrest at large calderas rarely ends in eruption, encouraging vulnerable communities to perceive emergency warnings of volcanic activity as false alarms. A classic example is the Campi Flegrei caldera in southern Italy, where three episodes of major uplift since 1950 have raised its central district by about 3 m without an eruption. Individual episodes have conventionally been treated as independent events, so that only data from an ongoing episode are considered pertinent to evaluating eruptive potential.

The "continuum" of a unified theory of diseases.

This essay's theme was inspired by a question asked by a child: 'Why do I get ill?' The question is very interesting, but has no easy answer. This paper discusses a few possible answers to this difficult question. Through the life of a person, from birth to death, there is a "continuum" in the pathological conditions a person may experience.