Mixed-valence Manganese Cluster Research Articles

Mixed-valence manganese cluster containing a sandwich-type polyoxometalate

Reaction of Na12[α-P2W15O56] · 18H2O with Mn(CH3COO)2 · 4H2O in the presence of K2S2O8 in acidic aqueous solution leads to isolation of a {} cluster-containing sandwich-type compound: αββα-K3Na11{(H2O)2(P2W15O56)2} · 40H2O (1). Single-crystal X-ray diffraction analysis revealed that 1 shows the well-known Weakley-type sandwich-type structure consisting of two trivacant [α-P2W15O56]12− Dawson moieties linked by a central symmetric rhomb-like mixed-valence manganese cluster via W–O–Mn and P–O–Mn connections. Mixed-valence Mn-cluster-substituted sandwich-type complexes based on trivacant Dawson units are rarely observed in polyoxometalate chemistry. Further, the sandwich-type polyoxoanions were connected by [K3Na2] clusters into a 44-layer. Magnetic study indicates that antiferromagnetic interactions exist in this compound.

New high-nuclearity manganese clusters containing mixed chelating ligands: Syntheses, crystal structures and magnetochemical characterization

Two polynuclear mixed-valence manganese clusters, [Mn(13)] and [Mn(16)], containing mixed chelating ligands were synthesized and structurally characterized. The alternating current (AC) susceptibilities of both complexes reveal nonzero frequency-dependent out-of-phase (χ(M)'') signals.

Ring Like Octadecanuclear Mixed‐valence Manganese Cluster with a Spin Ground State of 20

Big spin! In the presence of 2-aminopropane-1,2-diol, the reaction of 1,1,1-tris-(hydroxylmethyl)propane and [Mn(acac)2] in MeCN yielded a novel ring-like octadecanuclear mixed-valence manganese cluster complex, which exhibits an overall ferromagnetic property and possesses a large spin ground state of 20.

Langmuir-Blodgett Films of Magnetic Clusters

The mixed-valence manganese clusters [Mn12O12(carboxylato)16] have been organized in a multilayer architecture. Indeed, well-defined Langmuir-Blodgett (LB) films of the acetate and the benzoate Mn12 clusters can be obtained using behenic acid as organic matrix. Here, we report the magnetic properties of these multilayers, which present a marked hysteresis at 2 K.

Manganese clusters: a common ground for photosynthesis, quantum tunnelling of the magnetization and colossal magnetoresistance *

Mixed-valence manganese clusters are briefly reviewed, showing their relevance to such diverse fields as metalloenzymes and metalloproteins, single-molecule magnets, and colossal magnetoresistance. Particular emphasis has been given to the possibility of using high-field EPR spectroscopy for obtaining structural information from EPR-silent ions such as manganese(III). Besides the small clusters, comprising two–four metal ions relevant to biological systems, a large interest is invested in larger clusters, with the aim of showing how synthetic work aimed at obtaining models for biological clusters has provided many interesting results for other types of investigations.

Magnetically induced optical bi-stability of the molecular nanomagnet Mn12O12(OOCMe)16(H2O)4 in an organic glass

The magnetic hysteresis of the mixed-valence manganese cluster, Mn 12 O 12 (OOCMe) 16 (H 2 O) 4 , (Mn 12 ),1 a molecular superparamagnet,2 can be optically detected in a dilute, frozen organic glass below the blocking temperature of 3.8 K by magnetic circular dichroism spectroscopy.

Synthesis and structure of [Mn 6O 2(O 2CPh) 10(EtOH) 4(H 2O)] ·. EtOH, a manganese aggregate containing three types of benzoate ligation. Isomerism in [Mn 6O 2(O 2CPh) 10] complexes

The reaction of Mn(O 2CPh) 2·.4H 2O with KMnO 4 in warm ethanol in the presence of benzoic acid has been found to give, in addition to the previously reported “manganic benzoate”, the new hexanuclear mixed-valence manganese cluster [Mn 6O 2 (O 2CPh) 10(EtOH) 4(H 2O)]·.EtOH ( 1) in 40% yield. X-ray crystal structure determination at −172°C shows that the complex contains a distorted [Mn II 4Mn III 2O 2] 10+ core and, in addition to terminal EtOH and H 2O groups, three different types of benzoate ligation viz. μ 3-bridging, μ 2-bridging and monodentate terminal forms.

Mn2+/Mn3+ and Mn3+/Mn4+ mixed valence binuclear manganese complexes of biological interest

Binuclear and multinuclear manganese containing enzymes which occur in biology are involved in functions such as hydrogen peroxide decomposition in bacteria and the oxidation of water to oxygen during photosynthesis, respectively. In the case of the water-oxidizing complex, the so-called S/sub 2/ oxidation state has been characterized by EPR spectroscopy to be a mixed valence manganese cluster. This can be produced in two forms. The native form, which is found in active O/sub 2/-evolving samples, is considered to be either tetranuclear or trinuclear in Mn, based upon interpretation of its broad 1500 G-wide 19-line multiline EPR signal and unusual temperature dependence. A partially decoupled form is found in inactivated samples having a narrow width (1345 G), with only 16 lines and a more Curie-like temperature dependence, all features which are found in typical Mn/sup 3 +//M/sup 4 +/ binuclear centers (16-line EPR, spin S = 1/2 ground state). For the native form both different oxidation states and different numbers for the manganese ions in the cluster have been proposed in order to account for the larger spectral width due to the hyperfine interaction with /sup 55/Mn. Both binuclear Mn/sup 2 +//Mn/sup 3 +/ and tetranuclear/sup 4/ 3Mn/sup 3 +//Mn/sup 4more » +/ states have been considered. Notably lacking in this analysis has been EPR data for binuclear complexes in which both types of mixed valence oxidation states, Mn/sup 3 +//Mn/sup 4 +/ and Mn/sup 2 +//Mn/sup 3 +/, are compared within the same ligand system. The present report gives the first experimental evidence showing how /sup 55/Mn hyperfine data can easily distinguish between binuclear manganese complexes having these mixed valence oxidation states.« less