Erratum to: Determination of metal ion content of beverages and estimation of target hazard quotients: a comparative study

This is a correction to the following paper: Hague T, Petroczi A, Andrews PR, Barker J, Naughton DP: Determination of metal ion content of beverages and estimation of target hazard quotients: a comparative study. Chem Central J 2008, 2:13.     

Rational Improvement of Single-Molecule Magnets by Enforcing Ferromagnetic Interactions

The anisotropy barrier of polynuclear single-molecule magnets is expected to be higher with less tunneling the better stabilized the spin ground state is so that less M_S mixing in the ground state and with excited spin states occur. We have realized this experimentally in two structurally related heptanuclear SMMs: the triplesalen-based [Mn^III ₆ Cr^III]³⁺ and the triplesalalen-based *[Mn^III ₆ Cr^III]³⁺ . The ligand system triplesalen was developed to enforce ferromagnetic interactions by the spin-polarization mechanism. However, we found weak antiferromagnetic couplings, that we assigned to an inefficient spin-polarization by a heteroradialene formation. To prevent this heteroradialene formation, the triplesalalen ligand H₆talalen was designed. Here, we present the building block [(talalen )Mn^III₃]³⁺ and its application for the assembly of [{(talalen )Mn^III₃}₂{Cr^III(CN)₆}]³⁺ (= *[Mn^III ₆ Cr^III]³⁺ ). Both the trinuclear and heptanuclear complexes are SMMs. The comparison to the related triplesalen complex [(feld )Mn^III₃]³⁺ proves the absence of heteroradialene character and the enforcement of ferromagnetic Mn^III-Mn^III interactions in the (talalen )⁶⁻ complexes. This results in an increase of the barrier for spin reversal U_eff from 25 K in the triplesalen-based [Mn^III ₆ Cr^III]³⁺ SMMs to 37 K in the triplesalalen-based *[Mn^III ₆ Cr^III]³⁺ SMM proving the success of our concept. Based on this study, the next step in the rational improvement of our SMMs is discussed.     

Determination of metal ion content of beverages and estimation of target hazard quotients: a comparative study

Background  

Considerable research has been directed towards the roles of metal ions in nutrition with metal ion toxicity attracting particular attention. The aim of this study is to measure the levels of metal ions found in selected beverages (red wine, stout and apple juice) and to determine their potential detrimental effects via calculation of the Target Hazard Quotients (THQ) for 250 mL daily consumption.     

Bioinspired Enhancement of Superexchange: From 1,3,5-Trihydroxybenzene-Bridged to 1,3,5-Trimercaptobenzene-Bridged Trinuclear Copper(II) Complexes

An unprecedented trinucleating ligand with a central 1,3,5-trimercaptobenzene unit and its trinuclear Cu(II)(3) complex are presented. The high covalency of the difficult-to-realize Cu(II)-SR bond provides an order of magnitude increase in the superexchange interaction in comparison to its oxygen analogue.     

Synthesis and characterization of a trinuclear Cu(II)3 complex bridged by an extended phloroglucinol-ligand: implications for a rational enhancement of ferromagnetic interactions

The synthesis and characterization of the extended phloroglucinol-ligand H(3)felden based on the trialdehyde 2,4,6-triformylphloroglucinol and its trinuclear Cu(II)(3) complex [(felden){Cu(bpy)}(3)](ClO(4))(3) is presented. This study is motivated to optimize analogous extended phloroglucinol-ligands based on the triketone 2,4,6-triacetylphloroglucinol, which transmit ferromagnetic interactions by the spin-polarization mechanism between three Cu(II) ions and have therefore been applied as the central ligand backbone for a class of heptanuclear single-molecule magnets in a supramolecular approach. A detailed NMR spectroscopic study reveals that the ligand H(3)felden is not in the usually anticipated enol-imine form but in the tautomeric keto-enamine form. The presence of a C(3h) and a C(s) symmetric isomer results in a set of four different signals for each proton. In conjunction with FTIR, electronic absorption spectroscopy, and bond length considerations, it also appears that the complex [(felden){Cu(bpy)}(3)](ClO(4))(3) must be considered as a resonance hybrid of an enolate-imine and a keto-enamine form. A strong contribution of the keto-enamine resonance structure with loss of the central π system explains the weak but ferromagnetic interactions between the Cu(II)S = 1/2 spins. This detailed analysis identifies the strong resonance with unsaturated groups in 2,4,6-position of phloroglucinol as the main source for the low ferromagnetic couplings by the spin-polarization mechanism in these ligands. This provides a synthetic handle to improve the spin-polarization mechanism in these ligands by replacing the imine with amine functions.