Manganese Coordination Research Articles

2D hydrogen-bonded manganese–picolinate coordination network: ionic liquid-induced synthesis, crystal structure and thermogravimetric analysis

A new manganese coordination complex of formula [Mn(2-picolinate)2·2H2O]·H2O based on 2-picolinic acid has been synthesized hydrothermally at 120 °C for 48 h in presence of ionic liquid tetraethylammonium hydroxide (25% methanolic solution). 1 crystallizes in monoclinic crystal system and is hydrogen-bonded metal-organic network in which aqua ligands are instrumental in deciding structural features. The reported complex 1 is insoluble in almost all organic solvents as well as in water and shows good thermal stability upto 450 °C.

THIOCYANATE COMPLEXES OF d-METALS: INFLUENCE OF CONCENTRATION OF KNCS AND NH4Cl ON A TYPE OF COORDINATION OF SCN-IONS BY FTIR SPECTROMETRY

By IR spectrometry thiocyanates aqueous solutions of divalent cations of cadmium, mercury, nickel, manganese, iron, zinc and cobalt were studied. It was found that cadmium (II), mercury (II), nickel (II), iron (II) thiocyanate ions coordinated by type thiocyanate, zinc (II) − according to the type isothiocyanate; cobalt (II) and manganese (II) coordination mode change depending on the concentration of potassium thiocyanate in a solution. These results are consistent with the theory of hard and soft acids and bases. Co2+ ions are intermediate acids, so they can coordinate with SCN− into two types; Zn2+ ions, although they belong to intermediate acids but have a strong affinity to nitrogen atoms, so thiocyanate group coordinated through nitrogen with Zn2+. Cations Hg2+ and Cd2+ are typical soft acids, so only coordinated SCN− ions through sulfur (as a mild base). Mn2+ ions can coordinate SCN− by two types. The effect of additives of the ammonium chloride ions on thiocyanate ions (0.5 mol/l) coordination with cobalt (II) ions was studie. With the increasing concentration of ammonium chloride in a solution a change occurs of coordination type with thiocyanate to isothiocyanate. It has been suggested that the increase in the concentration of potassium thiocyanate leads to the increase in the proportion of Co(NCS)42− and reduce the proportion of «free» water (unrelated with ions in the solution). Therefore, SCN− ions in the case Mn2+ and Co2+ oriented so that the hydrophobic sulfur atoms are external ones.Forcitation:Matveichuk Yu.V., Rakhman′ko E.M. Thiocyanate complexes of d-metals: influence of concentration of KNCS and NH4Cl on a type of coordination of SCN− ions by FTIR spectrometry. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 7. P. 34-41.

Syntheses, structures and magnetic properties of one-dimensional manganese(II) complexes bridged by 2,2′-biphenyldicarboxylate

Two new manganese (II) complexes, namely {[Mn (dpa) (3-mepy)2]∙(H2O)}n (1) and {[Mn (dpa) (4-mepy)2]∙(H2O)}n (2) (dpa = 2,2′-biphenyldicarboxylate, 3-mepy = 3-methylpyridine, 4-mepy = 4-methylpyridine) were prepared and structurally characterized. The single-crystal X-ray diffraction analysis reveals that each manganese atom in 1 and 2 is coordinated by two nitrogen atoms from two substituted pyridines and four oxygen atoms from three crystallographically independent dpa ligands to offer distorted octahedral geometries. A one-dimensional manganese (II) coordination polymer of 1 and 2 was constructed by the bridging dpa ligands in a μ3-η1:η2:η1 coordination mode. Four lattice water molecules are interconnected through hydrogen bonding interactions to form a planar water tetramer in 1 and a linear water tetramer in 2. An antiferromagnetic exchange interaction of manganese (II) complexes 1 and 2 was investigated by the magnetic susceptibility measurement in the temperature range 1.80–300 K.

1-D calcium, 2-D zinc and 3-D manganese coordination polymers derived from pyrazine-2,3,5,6-tetracarboxylic acid

Three coordination polymers were synthesized from pyrazine-2,3,5,6-tetracarboxylic acid (H4pztc) in combination with calcium, zinc and manganese ions under hydrothermal conditions and their structures were determined by single crystal X-ray diffraction, powdered X-ray diffraction, Fourier transformed infrared spectroscopy, thermogravimetric and elemental analyses. Structure 1, {(Ca(H2pztc)(H2O)3)n, crystallizes as 1-D chains, with the partially deprotonated ligand in –O,N,O– coordination mode and with the Ca atoms in an uncommon nine coordinate environment. Structure 2, {Zn1(pztc)(H2O)2Zn2(H2O)4}n, is an infinite, 2-D coordination network that contains two nonequivalent Zn atoms, each with octahedral geometry, and the fully deprotonated pztc4− in bis-bridging chelating coordination mode. The stacked 2-D layers are stabilized by extensive inter-layer water-carboxylate hydrogen-bonding with an inter-layer distance of 4.9Å. Structure 3, {(Mn2(pztc)(H2O)2)}n, is a covalently bonded 3-D network containing two nonequivalent Mn atoms, each with octahedral geometry, and the fully deprotonated pztc4− units. Structure 3 exhibits paramagnetic behavior at room temperature, and weak antiferromagnetic properties at very low temperature, which is consistent with their nearest Mn…Mn separation distance of 4.9Å.

Two manganese(II) coordination polymers driven by (iso)nicotinoyl-hydrazone blocks and pseudohalide ancillary ligands: syntheses, structural features, and magnetic properties

Two coordination polymers, [Mn2(μ-L1)2(μ-N3)2]n (1) and [Mn(μ-HL2)(SCN)2]n (2), were assembled in a single-pot from MnCl2·4H2O, HL1 (2-acetylpyridine isonicotinoylhydrazone) or HL2 (2-acetylpyridine nicotinoylhydrazone) and ancillary ligand sources (NaN3 or NH4NCS). The products were fully characterized, including by single-crystal X-ray diffraction, which revealed a 2-D metal–organic layer in 1 and a 1-D zigzag coordination chain in 2. Both 1 and 2 are constructed from six-coordinate Mn(II) nodes that adopt distorted octahedral (MnN5O) environments; the adjacent nodes are driven by the μ-L1 and μ-N3 linkers in 1 or μ-HL2 linkers in 2 to form different metal–organic networks. Their topological classification was performed, disclosing the hcb and 2C1 topology in 1 and 2, respectively. Different weak non-covalent interactions promote dimensionality extension. Variable-temperature magnetic susceptibility measurements were carried out, revealing weak ferromagnetic and antiferromagnetic interactions in 1 and 2, respectively.

Zinc(ii), cobalt(ii) and manganese(ii) networks with phosphoserine ligand: synthesis, crystal structures and magnetic and proton conductivity properties.

A series of zinc(ii), cobalt(ii) and manganese(ii) coordination networks with phosphoserine ligand (H3PSer) are synthesized and characterized. Whereas in compounds 1 and 2 with the general formula [M(HPser)]n [M = Zn (1) and Co (2)], the metal(ii) ion presents a tetrahedral geometry, in [Co(HPSer)(H2O)2]n (3) and [Mn(HPSer)(H2O)]n (4), the metal(ii) ions are in a distorted octahedral geometry. The 3D frameworks are formed by inorganic layers built up from MO4 or MO6 polyhedra and phosphate groups. These layers are linked by the carboxylate groups of the phosphoserine ligand. The presence of extended hydrogen bonding stabilizes the 3D network and favours the proton transfer leading to moderate proton conductors. The highest proton conductivity, 2.70 × 10-5 S cm-1 (at 80 °C and 95% RH), is obtained for compound 3. Temperature-dependent magnetic susceptibility measurements for 2-4 reveal predominant antiferromagnetic interactions between the paramagnetic metal(ii) ions.

Combined influence of hydrogen bonds and π–π interactions on the assembly of five manganese coordination polymers with magnetic properties

Five novel interesting Mn(II) coordination polymers, [Mn3(IDPA)3(DMA)(H2O)2]n·n[(H2O)(DMA)] (1), [Mn(IDPA)(2,2′-bpy)(H2O)]n·2n(H2O) (2), [Mn(IDPA)(phen)(H2O)]n (3), [Mn(IDPA)(bpa)1/2(H2O)2]n·n(H2O) (4), and [Mn(IDPA)(4,4′-bpy)1/2]n (5) [H2IDPA = 5-(1-oxoisoindolin-2-yl) isophthalic acid, bpy = bipyridine, bpa = 1,2-bis(4-pyridyl)ethane, phen = 1,10-phenanthroline, DMA = N,N-dimethylacetamide], have been synthesized with different N-donor ligands under solvothermal conditions and structurally characterized. The crystal structures of 1–5 illustrate that hydrogen bonds and π–π interactions play critical roles in the construction of the extended supramolecular architectures. Compound 1 possesses a two-dimensional (2D) layer structure with a uninodal 4-connected sql tetragonal plane net. Compounds 2–4 feature one-dimensional chain (1D) structures, which further extend to 2D supramolecular networks via intermolecular π–π interactions and hydrogen bonds. Compound 5 exhibits a most remarkable and unique three-dimensional (3D) framework with a binodal (4,5)-connected new topology with the Schläfli symbol of {42·52·62}{42·53·64·7}. Interestingly, the carboxylic groups of H2IDPA display six different types of coordination modes in 1–5 and the steric bulk of H2IDPA plays an important role in influencing the structures of its compounds. Compound 1 containing triangular trinuclear (Mn1⋯Mn2⋯Mn3) units displays weak antiferromagnetic interactions in the system, whereas compounds 2–5 show that the overall magnetic interactions among the Mn(II) ions are weakly ferromagnetic. Besides, the thermal stabilities and luminescence properties of 1–5 have also been investigated and discussed in detail.

Synthesis, X-ray structure and theoretical investigation of 2-(2’-quinolyl)benzimidazole metal complexes

Synthesis, characterization and DFT analysis of 2-(1H-benzo[d]imidazol-2-yl)quinoline (BQ) and its cobalt and manganese coordination compounds {Co(DMF)(BQ) Cl 2} and {Mn(DMF)(BQ) Cl 2} have been described. The ligand, 2-(1H-benzo[d]imidazol-2-yl)quinoline (BQ) crystallizes in non-centrosymmetric monoclinic crystal system with cell parameters a = 12.9280(4) Å, b = 7.9429(3) Å, c = 25.8478(9) Å, α = γ=90∘,β=103.005(2)∘. {Co(DMF)(BQ)Cl 2} and {Mn(DMF)(BQ)Cl 2} crystallized in triclinic space group P-1. The metal(II) environment exhibits trigonal bipyramidal coordination. These complexes show presence of N–H …Cl, C–H...Cl hydrogen bonds and strong intramolecular C–H...O interactions. The structure parameters were calculated and they are in good agreement with those observed experimentally. Theoretically calculated frontier molecular orbitals (HOMO–LUMO) of the complexes and their energies indicate intermolecular charge transfer and delocalization of electron density within the molecule. Synthesis, characterization and DFT analysis of 2-(1H-benzo[d]imidazol-2-yl)quinoline (BQ) and its cobalt and manganese coordination compounds {Co(DMF)(BQ)Cl2} and {Mn(DMF)(BQ)Cl2} have been described. Theoretically calculated frontier molecular orbitals (HOMO-LUMO) of both complexes indicate intermolecular charge transfer and delocalization of electron density within the molecule.

Synthesis, structures, and magnetic properties of two closely-related manganese(II) coordination polymers

The reactions of Mn2+ ion with 4-nitrobenzene-1,2-bicarboxylic acid in the presence of bipyridyl-type coligands gave two new manganese(II) coordination polymers, [Mn2(Nbdc)2(Bipyp)(H2O)4] n (I) and [Mn2(Nbdc)2(Bipye)(H2O)4] n (II) (H2Nbdc = 4-nitrobenzene-1,2-bicarboxylic acid, Bipyp = 1,3-bi(4-pyridyl)propane, and Bipye = 1,2-bi(4-pyridyl)ethane). Both two complexes contain uniform carboxyl-bridged manganese chains with the composition of [Mn2(Nbdc)2(H2O)4] n , which are interlinked by interchain Bipyp/Bipye spacers to afford two closely-related layers (CIF files CCDC nos. 1008182 (I) and 1008183 (II)). Magnetic studies for two compounds show the presence of similar antiferromagnetic couplings between the adjacent Mn2+ ions through the carboxyl bridges, the best fittings to the experimental magnetic susceptibilities gave J =–0.20 cm–1 and g = 1.96 for I, and J =–0.24 cm–1 and g = 1.98 for II. Similar magnetic parameters and thermal behaviors further verify that two compounds possess closely-related structures.

A new three-dimensional manganese(II) coordination polymer based on the 1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene ligand.

The self-assembly of coordination polymers and the crystal engineering of metal-organic coordination frameworks have attracted great interest, but it is still a challenge to predict and control the compositions and structures of the complexes. Employing multidentate organic ligands and suitable metal ions to construct inorganic-organic hybrid materials through metal-ligand coordination and hydrogen-bonding interactions has become a major strategy. Recently, imidazole-containing multidentate ligands that contain an aromatic core have received much attention. A new three-dimensional MnII coordination polymer based on 1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene, namely poly[(ethane-1,2-diol-κO)(μ-sulfato-κ2O:O'){μ3-1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene-κ3N:N':N''}manganese(II)], [Mn(SO4)(C18H18N6)(C2H6O2)]n, was synthesized and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Crystal structural analysis shows that there are two kinds of crystallographically independent MnII centres, each lying on a centrosymmetric position and having a similar six-coordinated octahedral structure. One is coordinated by four N atoms from four 1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene (timb) ligands and two O atoms from two different bridging sulfate anions. The second is surrounded by two timb N atoms and four O atoms, two from sulfate anions and two from two ethane-1,2-diol ligands. The tripodal timb ligand bridges neighbouring MnII centres to generate a two-dimensional layered structure running parallel to the ab plane. Adjacent layers are further bridged by sulfate anions, resulting in a three-dimensional structure with 3,4,6-c topology. Thermogravimetric analysis of the title polymer shows that it is stable up to 533 K. The first weight loss between 533 and 573 K corresponds to the release of coordinated ethane-1,2-diol molecules, and further decomposition occurred at 648 K.

Modification of the structure and magnetic properties of fumarato-bridged Mn coordination polymers through different dimethyl-2,2′-bipyridine co-ligands

Manganese coordination polymers {Mn(fum)(5dmb)(H2O)2} n (1) and {[Mn2(fum)2(4dmb)2]·H2O} n (2) (fum = fumarato; 5dmb = 5,5′-dimethyl-2,2′-bipyridine; 4dmb = 4,4′-dimethyl-2,2′-bipyridine) were obtained from one-pot, solution reactions under ambient conditions. The fum ligand acquires different coordination modes in the presence of the different dmb ancillary ligands, promoting distinctive crystal structures, including divergent dimensionalities. Thus, X-ray single-crystal data reveal that complex 1 crystallizes in a monoclinic system with C2/c space group and forms an infinite one-dimensional polymer. The Mn(II) center is six-coordinated and displays a distorted octahedral configuration. In addition, the solid-state self-assembly of the polymeric structure of 1 gives rise to a two-dimensional (2D) supramolecular framework, mainly through hydrogen bonding. In contrast, complex 2 crystallizes in a monoclinic system with a Cc space group and forms an infinite 2D coordination polymer having dinuclear units. The Mn(II) center has a distorted octahedral configuration. The thermal stabilities of both coordination polymers were investigated. Variable-temperature magnetic measurements show that complex 1 is paramagnetic, while complex 2 exhibits weak antiferromagnetic coupling between adjacent Mn(II) centers.

16O/18O oxygen isotope exchange kinetics in MnO 4 − as probed by 55Mn NMR

The effect of the 16O ↔ 18O substitution in the coordination sphere of permanganate anion MnO4− on the chemical shift of 55Mn nuclei have been studied by 17O and 55Mn NMR. Time constants τn,k of oxygen exchange in the water–permanganate anion system have been estimated. In nearly neutral solutions (pH ≈ 6.8–7.2), the oxygen exchange time is on the order of tens of hours. Bubbling gaseous HCl through this solution for a few seconds leads to the equilibrium distribution of oxygen isotopes in the manganese coordination sphere. The observed temperature dependences of isotope-induced 55Mn NMR shifts in Mn16 O44-n18On– (n = 0–4) have been treated as a result of rovibrational averaging of Mn–O bond lengths. The change in the Mn—O bond length in caused by the 16O → 18O isotope substitution is on the order of 10–4 A.

Synthesis, crystal structures and catalytic properties of three-dimensional nickel(II) and manganese(II) coordination polymers with dicarboxylate and semi-rigid bis(imidazole) ligands

Two coordination polymers (CPs), namely [Ni(L)(chdc)] n (1) and [Mn(L)(ndc)(H2O)] n (2) (L = 4,4′-bis(imidazol-1-ylmethyl)biphenyl, H2chdc = 1,2-cyclohexanedicarboxylic acid, H2ndc = 2,6-naphthalenedicarboxylic acid), have been hydrothermally synthesized and characterized by physicochemical and spectroscopic methods and also by single-crystal diffraction. Both CPs feature 3D-diamond-like networks with point symbol of 66; CP-1 displays a 2-fold interpenetrated net, while CP-2 presents a non-interpenetrated framework. The thermal stabilities, solid-state luminescence properties and catalytic activities of both CPs for degradation of methyl orange in a Fenton-like process were investigated.

Ligand-to-Ligand Charge Transfer within Metal-Organic Frameworks Based on Manganese Coordination Polymers with Tetrathiafulvalene-Bicarboxylate and Bipyridine Ligands.

A systematic study on ligand-to-ligand charge-transfer (LLCT) properties of three closely related metal-organic frameworks (MOFs) is presented. These compounds are formulated as [MnL(4,4'-bpy)(H2O)]n·nCH3CN (1), [MnL(bpe)0.5(DMF)]n·2nH2O (2), and [MnL(bpa)(H2O)]n·2nH2O (3) (L = dimethylthio-tetrathiafulvalene-bicarboxylate, 4,4'-bpy = 4,4'-bipyridine, bpe = 1,2-bis(4-pyridyl)ethene, bpa = 1,2-bis(4-pyridyl)ethane). The X-ray single-crystal diffractions show that complexes 1-3 are all two-dimensional (2-D) coordination polymers with different frameworks in crystal lattices. Charge-transfer (CT) interactions within these MOFs are visually apparent in colors and vary according to the conjugated states of the bipyridine ligands (4,4'-bpy, bpe, and bpa). Theoretical calculations show that the charge transfer occurs from ligand L to bipyridine. The intensity of the LLCT is in the order of 2 > 1 > 3 investigated by theoretical calculations and ESR, which indicates that the intensity of CT is related to the bipyridyl conjugated state. Photocurrent responses of these compounds are consequently studied, and the results are in agreement with the intensity of charge transfer and linearly related to the LLCT energy.

Solvent‐Controlled Construction of Two 3D Manganese(II) Coordination Polymers Based on Flexible Tripodal Multicarboxylate Linker and Rod‐Shaped SBUs

AbstractTo further explore the coordination possibilities of the flexible tripodal ligand, 4,4′,4′′‐(benzene‐1,3,5‐triyl‐tris(oxy))tribenzoic acid (H3BTTB), two solvent‐controlled three‐dimensional (3D) manganese(II) coordination polymers, [Mn3(BTTB)2(H2O)4](H2O)2 (1) and [Mn3(BTTB)2(DMF)2](DMF)2 (2), were synthesized and characterized. Single crystal X‐ray diffraction analysis indicates that in the MnII complexes the BTTB ligands exhibit two coordination modes, which have not been reported previously. Complexes 1 and 2 involve different one‐dimensional (1D) rod‐shaped metal–carboxylate secondary building units (SBUs). The 1D SBUs are further extended to afford two different three‐dimensional (3D) frameworks with similar flu topology via linkage of the BTTB ligands. The results demonstrate that the reaction solvent as well as conformation and coordination mode of BTTB ligands play key roles on the formation of the final framework structures. Additionally, their luminescent properties were investigated.

Syntheses, structures and properties of nickel(II) and manganese(II) coordination polymers based on V-shaped bis-imidazole and aromatic carboxylate ligands

Using V-shaped mixed ligands bis-imidazole and aromatic carboxylic acids, five new coordination polymers namely, {[Ni(B-im)(Br-a)Cl]·H2O}n (1), {[Ni(B-im)(I-a)(H2O)2]·0.5H2O}n (2), [Ni(B-im)(I-a)(H2O)2]n (3), [Ni(B-im)(M-a)(H2O)2]n (4) and {[Mn2(B-im)2(I-a)2]·2H2O}n (5) [B-im=1,1′-(5-methyl-1,3-phenylene)bis(1H-imidazole), Br-a=5-bromonicotinic acid, I-a=isophthalic acid and M-a=5-methylisophthalic acid] were solvothermally synthesized and fully characterized by IR spectra, element analyses, X-ray powder and single-crystal diffractions, and thermogravimetric analyses. Complexes 1 and 2 feature polymeric macrocyclic chain structures containing interesting nanotubular channels, which are constructed by bridging 30-membered macrocyclic [Ni3(B-im)3] subunits with Br-a ligands and by bridging folded 20-membered macrocyclic [Ni2(B-im)2] subunits with I-a ligands, respectively. Isomorphic complexes 3 and 4 represent double-chain structures containing folded 18-membered macrocyclic [Ni2(B-im)(I-a)] subunits and [Ni2(B-im)(M-a)] subunits, respectively. Complex 5 is a 2D porous coordination polymer containing novel chiral four-stranded Mn(II) chains consisting of two (B-im)-bridged aspiral chiral chains and two (I-a)-bridged heterochiral coaxial 21-helical chains. The results of thermal gravimetric analyses suggest that the dehydrated frameworks of 1–5 are stable up to 320°C. Additionally, the magnetism of complexes 3 and 5 were also investigated.

One Novel 2D Manganese(II) Coordination Polymer From Carboxylphenyl Imidazole Dicarboxylate: Synthesis, Crystal Structure, and Properties

One Mn(II) coordination polymer, [Mn(p-CPhH2IDC)(H2O)]n (1) (p-CPhH4IDC = 2-(4-carboxylphenyl)-1H-imidazole-4,5-dicarboxylic acid), has been solvothermally synthesized and structurally characterized by elemental analysis, IR spectrum, as well as single-crystal X-ray diffraction analysis. The polymer can be regarded as a 2D sheet structure. Further, the solid-state photoluminescence and thermal properties of the polymer have been investigated.

Manganese(II) coordination polymer having pyrazine and μ-phenolato bridging: Structure, magnetism and biological studies

The manganese(II) coordination polymer, {[Mn(L)(pyz)]ClO4·2(H2O)}n. (1) has been synthesized from a mixture of Mn(ClO4)2·6H2O, Schiff base HL (derived from the condensation of 4-aminoantipyrine and salicylaldehyde) and pyrazine (pyz). Its molecular structure was determined by single crystal X-ray diffraction, which reveals that the polymeric structure consists of simultaneous Mn–Pyz–Mn and Mn–O(phenoate)–Mn bridges between the metal centers. Variable temperature magnetic studies give g=2.037(4), J=−1.90(4)cm−1, ϑ=0.5K values, using a simple dinuclear Mn–Mn model, and indicates that the major exchange pathway is via the two phenoxide bridges and the pyrazine has little influence. The coordination polymer also shows enhanced antibacterial activity compared with the standard antibiotic levofloxacin.

Light- or oxidation-triggered CO release from [MnI(CO)3(κ3-L)] complexes: reaction intermediates and a new synthetic route to [Mn(μ-O)2(L)2] compounds.

The reaction products and intermediates of the three CO-releasing manganese(i) coordination compounds [Mn(tpm)(CO)3]+, [Mn(bpza)(CO)3] and [Mn(tpa)(CO)3]+ were analysed by combining IR-spectroscopy, electrochemical measurements and single-crystal XRD. The intermediate formation of manganese(i) biscarbonyl compounds and the rather facile oxidation of these species were identified as key reaction steps that accompany CO liberation. For the use of [MnI(CO)3] complexes as light-triggered CO sources, the results indicate that in this case photo- and redox-chemistry seem to be strongly coupled which could be important and potentially even useful in the pharmacological context. Additionally, one has to be aware of the fact that [MnII(κ3-L)(solv)3]2+ complexes, the primary reaction products after CO substitution, are able to bind to proteins, which was demonstrated using bovine serum albumin as a model. And finally it could be shown that the CO-release reactions can be used as a new synthetic route to prepare multinuclear μ-oxido-bridged manganese complexes: the mixed-valence compound [Mn(μ-O)2(tpa)2]3+ could be prepared in a single step from [Mn(tpa)(CO)3]+via photo- or electrochemically induced CO substitution.

Manganism and Parkinson's disease: Mn(II) and Zn(II) interaction with a 30-amino acid fragment.

A protected 30-amino acid fragment, Acetyl-SPDEKHELMIQLQKLDYTVGFCGDGANDCG-Amide, Acetyl-Ser-Pro-Asp-Glu-Lys-His-Glu-Leu-Met-Ile-Gln-Leu-Gln-Lys-Leu-Asp-Tyr-Thr-Val-Gly-Phe-Cys-Gly-Asp-Gly-Ala-Asn-Asp-Cys-Gly-Amide, encompassing the sequence from residues 1164 to 1193 in the encoded protein from Parkinson's disease gene Park9 (YPk9), was studied for manganese and zinc binding. Manganese exposure is considered to be an environmental risk factor connected to PD and PD-like syndrome. Research into the genetic and environmental risk factors involved in disease susceptibility has recently uncovered a link existing between Park9 and manganese. It seems that manganese binding to Park9 (YPk9) protein is involved in the detoxification mechanism exerted by this protein against manganese toxicity. In this study, we used potentiometric, mono- and bi-dimensional (TOCSY, HSQC) NMR, EPR and ESI-MS measurements to analyze complex formation and metal binding sites in the peptide fragment. Presumably octahedral species, in which the Mn(II) ion was bound to oxygens of the carboxyl groups of Glu and Asp, and species where the involvement of sulfur from Cys and nitrogen from His residues, depending on the metal to ligand molar ratio, were detected for manganese coordination. Structural changes in the 30-amino acid fragment were triggered by Zn(II) interaction. A general decrease in the intensity of NMR signals was detected, suggesting the occurrence of chemical exchange among some coordinated species in an intermediate NMR timescale. The coordination may involve both S and N donor atoms from cysteine as well as histidine residues, together with O donor atoms from glutamic and aspartic residues.