A new, dinuclear high spin manganese(III) complex with bridging phenoxy and methoxy groups. Structure and magnetic properties

Water oxidation catalyzed by molecular di- and nonanuclear Fe complexes: importance of a proper ligand framework

The synthesis of two molecular iron complexes, a dinuclear iron(iii,iii) complex and a nonanuclear iron complex, and their use as water oxidation catalysts is described.

Dinuclear manganese complexes for water oxidation: evaluation of electronic effects and catalytic activity

During recent years significant progress has been made towards the realization of a sustainable and carbon-neutral energy economy. One promising approach is photochemical splitting of H2O into O2 and solar fuels, such as H2. However, the bottleneck in such artificial photosynthetic schemes is the H2O oxidation half reaction where more efficient catalysts are required that lower the kinetic barrier for this process. In particular catalysts based on earth-abundant metals are highly attractive compared to catalysts comprised of noble metals. We have now synthesized a library of dinuclear Mn2(II,III) catalysts for H2O oxidation and studied how the incorporation of different substituents affected the electronics and catalytic efficiency. It was found that the incorporation of a distal carboxyl group into the ligand scaffold resulted in a catalyst with increased catalytic activity, most likely because of the fact that the distal group is able to promote proton-coupled electron transfer (PCET) from the high-valent Mn species, thus facilitating O-O bond formation.

New series of monoamidoxime derivatives displaying versatile antiparasitic activity

Following the promising antileishmanial results previously obtained in monoamidoxime series, a new series of derivatives was synthesized using manganese(III) acetate, Wittig reactions and Suzuki-Miyaura cross coupling reactions. Pharmacomodulation in R(1), R(2) or R(3) substituents on the amidoxime structure is shown to influence antiprotozoan activity in vitro: a monosubstituted phenyl group in R1 (32-35) led to an activity against Leishmania donovani promastigotes (32, IC50 = 9.16 μM), whereas a polysubstituted group (36-37) led to an activity against Plasmodium falciparum (36, IC50 = 2.76 μM). Modulating chemical substituents in R(2) and R(3) only influenced the antiplasmodial activity in vitro. This suggests that the amidoxime scaffold has properties that could make it a promising new antiparasitic pharmacophore.

Ferromagnetic dinuclear mixed-valence Mn(II)/Mn(III) complexes: building blocks for the higher nuclearity complexes. structure, magnetic properties, and density functional theory calculations

A series of six mixed-valence Mn(II)/Mn(III) dinuclear complexes were synthesized and characterized by X-ray diffraction. The reactivity of the complexes was surveyed, and structures of three additional trinuclear mixed-valence Mn(III)/Mn(II)/Mn(III) species were resolved. The magnetic properties of the complexes were studied in detail both experimentally and theoretically. All dinuclear complexes show ferromagnetic intramolecular interactions, which were justified on the basis of the electronic structures of the Mn(II) and Mn(III) ions. The large Mn(II)-O-Mn(III) bond angle and small distortion of the Mn(II) cation from the ideal square pyramidal geometry were shown to enhance the ferromagnetic interactions since these geometrical conditions seem to favor the orthogonal arrangement of the magnetic orbitals.

What controls the magnetic interaction in bis-μ-alkoxo Mn(III) dimers? A combined experimental and theoretical exploration

The synthesis and magnetic characterisation of a series of bis-μ-alkoxide bridged Mn(III) dinuclear complexes of general formula [Mn(III)(2)(μ-OR)(2)(biphen)(2)(ROH)(x)(L)(y)] (where R = Me, Et; H(2) biphen = 2,2'-biphenol and L = terminally bonded N-donor ligand) is described, doubling the literature basis set for this type of complex. Building on these findings we have categorised all known μ-OR bridged Mn(III) dinuclear complexes into one of three classifications with respect to their molecular structures. We have then employed DFT and MO calculations to assess all potential magneto-structural correlations for this class of compound in order to identify the structural requirements for constructing ferromagnetic family members. Our analysis indicates that the most influential parameter which governs the exchange interaction in this class of compounds is the relative orientation of the JT axes of the Mn(III)  atoms. A perpendicular orientation of the JT axes leads to a large ferromagnetic contribution to the exchange. These results also suggest that a large ferromagnetic interaction and a large anisotropy are unlikely to co-exist in such structural types.