Trinuclear Manganese Research Articles

Retraction: Introduction of a trinuclear manganese(iii) catalyst on the surface of magnetic cellulose as an eco-benign, efficient and reusable novel heterogeneous catalyst for the multi-component synthesis of new derivatives of xanthene.

[This retracts the article DOI: 10.1039/D0RA09420J.].

Trinuclear manganese and zinc clusters and a dinuclear manganese complex with multiple oxo-bridges: Syntheses, structures, and magnetic properties of the MnII compounds and luminescent property of the ZnII complex

Two trinuclear clusters [Mn3(L1)2] (1) and [Zn3(L1)2] (2) have been prepared from the reactions of Mn(CH3COO)2·4H2O and Zn(CH3COO)2·4H2O, respectively, with a hydroxy-rich Schiff-base ligand H3L1 (H3L1 = 2-{[bis(2-hydroxy-3-methoxybenzyl)(amino-ethyl)amino]methyl}phenol). One dinuclear compound [Mn2(HL2)Cl2] (3) was synthesized from the treatment of MnCl2·4H2O with another hydroxy-rich Schiff base ligand H3L2 (H3L2 = 2-{[bis(2-hydroxy-3-methoxybenzyl)(amino-ethyl)amino]ethyl}phenol). Complexes 1–3 were characterized by single-crystal X-ray diffraction analysis. The structural analyses indicated that complexes 1 and 2 are isostructural and contain linear MnII–MnII–MnII and ZnII–ZnII–ZnII cores. In compounds 1–3, the metal centers are doubly bridged by phenoxido groups of the ligands. Variable temperature magnetic measurements of 1 and 3 revealed the presence of antiferromagnetic intramolecular couplings, and the magnetic susceptibility data are consistent with S = 5/2 of the MnII ions. The luminescent property of compound 2 was investigated. The 3d10 zinc compound 2 exhibited strong luminescence with λmax = 491 nm (for λex = 418 nm).

Pyrolysis of Schiff‐Base Manganese Clusters: Effect of Ligand Modulation on the Performance of Supercapacitor Electrodes

AbstractLigand modulation on metal organic clusters endow them with different physical and chemical properties, while how ligand modulation further affects the electrochemical behavior of pyrolytic derivatives is still unclear. Herein, we constructed two trinuclear manganese clusters 1‐Mn3 [Mn3L12(Cl)2] [L1=N1,N3‐bis(3‐methoxysalicylidene) diethylenetriamine] and 2‐Mn3 [Mn3L22(C7H4O2)2] [L2=N1,N3‐bis(3‐salicylidene) diethylenetriamine] based on nitrogen‐rich Schiff‐base pentadentate ligands. The introduction of TG‐MS (thermogravimetry associated with mass spectroscopy) explores the difference and universality of the pyrolysis mechanism of two trinuclear manganese clusters, and divides the pyrolysis process into three Areas (Area I/II/III) according to temperature. Combined with other characterization techniques, the materials in these three areas were analyzed to explain the effect of ligand modification on the electrochemical properties of cluster pyrolysis derivatives. It is found that the Area III derivatives have the best capacitance performance, when the current density is 1 A g−1, the specific capacitance of 1‐900 is 1717 F g−1, and 2‐900 is 350 F g−1. By comparison of the phase evolution process and electrochemical performance of the two manganese clusters, it is proposed that the crumbling of the molecular structure and stacking mode of trinuclear manganese clusters during pyrolysis will affect the capacitive properties of the derivatives. This work provides a guidance for the differences of the properties of pyrolytic derivatives under ligand modulation.

Hexagonal Layer Manganese Metal-Organic Framework for Photocatalytic CO2 Cycloaddition Reaction.

A novel manganese metal–organic framework (Mn-MOF) termed UAEU-50 assembled from a benzenedicarboxylate linker (BDC) and trinuclear manganese clusters was synthesized and fully characterized using different spectroscopic and analytic techniques (e.g., X-ray powder diffraction, UV–vis diffuse reflectance spectroscopy, thermogravimetric analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy). UAEU-50 adopted a hexagonal layer structure and exhibited superior thermal stability and robust chemical stability. Photocatalytic activities of UAEU-50 were investigated using the cycloaddition of CO2 to different epoxides, forming cyclic carbonates. Impressively, UAEU-50 can transform up to 90% photocatalytic CO2 conversion to cyclic carbonates in the visible-light region at ambient conditions.

Synthesis and Magnetic Properties of Two‐Step‐Coordination Schiff Base Clusters

AbstractA new family of paramagnetic coordination compounds based on a diimine‐pyridine pincer ligand has been prepared, using a two‐step synthetic approach. The sequential introduction of identical or different transition metals (Co, Mn, Ni, Zn) afforded mono‐, di‐, tri‐ and tetranuclear clusters, whose crystal structure has been determined. Magnetic studies reveal that the metals within the trinuclear manganese cluster engage in a small ferromagnetic exchange interaction (J=0.15 K). These studies enable the design of new clusters with specific magnetic properties.

Introduction of a trinuclear manganese(iii) catalyst on the surface of magnetic cellulose as an eco-benign, efficient and reusable novel heterogeneous catalyst for the multi-component synthesis of new derivatives of xanthene.

In this work, the new trinuclear manganese catalyst defined as Fe3O4@NFC@NNSM-Mn(iii) was successfully manufactured and fully characterized by different techniques, including FT-IR, XRD, TEM, SEM, EDX, VSM, and ICP analysis. There have been reports of the use of magnetic catalysts for the synthesis of xanthine derivatives. The critical potential interest in the present method include short reaction time, high yields, recyclability of the catalyst, easy workup, and the ability to sustain a variety of functional groups, which give economical as well as ecological rewards. Also, the synthesized catalyst was used as a recyclable trinuclear catalyst in alcohol oxidation reactions at 40 °C. The magnetic catalyst activity of Fe3O4@NFC@NNSM-Mn(iii) could be attributed to the synergistic effects of the catalyst Fe3O4@NFC@NNS-Mn(iii) with melamine. Employing a sustainable and safe low temperature, using an eco-friendly solvent, no need to use any additive, and long-term stability and magnetic recyclability of the catalyst for at least six successive runs are the advantages of the current protocol towards green chemistry. This protocol is a benign, environmentally friendly method for heterocycle synthesis.

Syntheses, structures, DNA/BSA binding and cytotoxic activity studies of chiral alcohol-amine Schiff base manganese (II/III) complexes

Four new mixed-valence manganese complexes, [Mn(II)Mn(III)2(S-L1)2(OAc)4]·2H2O(1), [Mn(II)Mn(III)2(R-L1)2(OAc)4]·2H2O (2), [Mn(II)Mn(III)2(2H2O)(S-L2)2(OAc)4] (3), [Mn(II)Mn(III)2(2H2O)(R-L2)2(OAc)4] (4) [H2L1 derived from (R)/(S)-2-amino-1-butanol and 2-hydroxy-5-chlorobenzaldehyde, H2L2 derived from (R)/(S)-2-amino-3-phenyl-1-propanol and 2-hydroxy-4-methoxybenzaldehyde], were synthesized and fully characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. Complexes 1–4 are mixed-valence trinuclear manganese compounds with six-coordinated. The linear MnIII–MnII–MnIII cores are triply bridged by acetate, phenolate and alkoxy groups. The vitro cytotoxicity test revealed that all complexes have substantial cytotoxic activity against three cancer cell lines (HepG2, MDA-MB-231 and A549). DNA-binding properties of 1–4 were investigated by UV–Vis, fluorescence spectroscopy, viscosity and thermal denaturation. All complexes bound to calf thymus DNA (CT-DNA) via an intercalative mode, and that derived from (S)-Schiff base ligands exhibited stronger interaction with DNA than (R)-isomers. Furthermore, the interactions of 1–4 with bovine serum albumins (BSA) in a static mode were also studied using absorption emission spectral techniques and molecular docking analysis. The chirality and structure of ligands showed to a large influence on the DNA/BSA binding ability and cytotoxicity of manganese complexes. The geometry optimization results are in agreement with experimental observations.

Self-assembled three-dimensional molecule-based magnet composed of a trinuclear manganese unit and octacyanidotungstate

We report a three-dimensional molecule-based magnet, [MnII3(4-pyridone)6][WV(CN)8]2·2H2O. This compound was synthesized in one-pot by evaporation of an aqueous solution in which MnCl2·4H2O, 4-hydroxypyridine and Cs3[W(CN)8]·2H2O were dissolved. The evaporation process causes self-assembly of the building blocks, forming a three-dimensional network structure with unique trimanganese units of [Mn3(4-pyridone)6]6+ bridged by [W(CN)8]3− anions. This compound has two types of short intermetallic bridges, which can exhibit two magnetic interaction pathways (MnII-O-MnII and MnII-NC-WV). The magnetic interactions between WV (S = 1/2) and MnII (S = 5/2) and between MnII and MnII are antiferromagnetic with exchange coupling constants of JMnW = −3.9 cm−1 and JMnMn = −5.9 cm−1, respectively. The present compound exhibits ferrimagnetism with spontaneous magnetization below 20 K.

Synthesis, crystal structures and electrochemical properties of Co(II) and Mn(II) complexes with asymmetric bulky BIAN ligands

Series of newly designed Co(II) and Mn(II) complexes supported by sterically encumbered asymmetric bis(imino)acenaphthene (BIAN) ligands were synthesized through the reaction of metal dichlorides with the corresponding ligands. The metal complexes were characterized by X-ray crystallography, UV–Vis, FT-IR and NMR spectroscopy. The molecular structures of Co1–Co10 all feature tetrahedral coordination geometry around cobalt. In contrast, the Mn compounds were demonstrated to show much diverse compositions and solid-state structures. By variation of the ligands and solvents used, mononuclear, binuclear or trinuclear manganese complexes could be isolated. Furthermore, the cyclic voltammograms for the Co and Mn complexes show two successive ligand-based single-electron redox processes, and the reduction potentials could be finetuned by changing the electronic property of the para-substituents on the central aryl ring of BIAN N-aryl groups.

Manganese trinuclear clusters based on schiff base: Synthesis, characterization, magnetic and electrochemiluminescence properties

Abstract Four novel linear trinuclear manganese clusters [Mn3(Ln)2(CH3COO)4] (1, n = 1; 2, n = 2; 3, n = 3; 4, n = 4. where HL1 is 4-chloro-2-((2-(6-chloropyridin-2-yl)hydrazono)methyl)phenol, HL2 is 4-bromo-2-((2-(6-chloropyridin-2-yl)hydrazono)methyl)phenol, HL3 is 4-chloro-2-((2-(6-bromopyridin-2-yl)hydrazono)methyl)phenol, HL4 is 4-bromo-2-((2-(6-bromopyridin-2-yl) hydrazono)methyl)phenol) were synthesized through solvothermal method. Complexes 1–4 were characterized by IR, and X-ray single-crystal diffraction. Complexes 1–4 are isomorphous compounds which are trinuclear linear manganese clusters. A detailed analysis of Hirshfeld surface and 2D fingerprint plots revealed that 1–4 were supported mainly by H⋯H, H⋯X (X = Cl, Br) and O⋯H intermolecular interactions. Magnetic properties of 1–4 have been studied. In additional, complex 3 showed highly intense electrochemicaluminescence (ECL) in DMF solution.

Intramolecular C-H and C-F Bond Oxygenation by Site-Differentiated Tetranuclear Manganese Models of the OEC.

The dangler manganese center in the oxygen-evolving complex (OEC) of photosystem II plays an important role in the oxidation of water to dioxygen. Inspired by the structure of the OEC, we synthesized a series of site-differentiated tetra-manganese clusters [LMn3(PhPz)3OMn][OTf]x (2: x = 2; 3: x = 1) that features an apical manganese ion-distinct from the others-that is appended to a trinuclear manganese core through an μ4-oxygen atom bridge. This cluster design was targeted to facilitate studies of high-valent Mn-oxo formation, which is a proposed step in the mechanism for water oxidation by the OEC. Terminal Mn-oxo species-supported by a multinuclear motif-were targeted by treating 2 and 3 with iodosobenzene. Akin to our previously reported iron complexes, intramolecular arene hydroxylation was observed to yield the C-H bond oxygenated complexes [LMn3(PhPz)2(OArPz)OMn][OTf]x (5: x = 2; 6: x = 1). The fluorinated series [LMn3(F2ArPz)3OMn][OTf]x (8: x = 2; 9: x = 1) was also synthesized to mitigate the observed intramolecular hydroxylation. Treatment of 8 and 9 with iodosobenzene results in intramolecular arene C-F bond oxygenation as judged by electrospray ionization mass spectrometry. The observed aromatic C-H and C-F hydroxylation is suggestive of a putative high-valent terminal metal-oxo species, and it is one of the very few examples capable of oxygenating C-F bonds.

Metal–organic frameworks based on tri- and penta-nuclear manganese(ii) secondary building units self-assembled by a V-shaped silicon-containing dicarboxylate

SBUs consisting in penta- or trinuclear manganese(ii) are held together by cpdps2- or cpdps2- and Hcpdps- species derived from bis(p-carboxyphenyl)diphenylsilane in 2D (4,4) coordination polymers. Magnetic, thermal and moisture behaviors are studied.

Influence of Steric Hindrance of N‐Heterocyclic Ancillary Ligands on the Structure and Magnetic Properties of Manganese(II) Coordination Polymers

AbstractThree biphenyl‐3,5‐dicarboxylic acid (H2L) based coordination polymers, namely, [Mn3(L)3(2,2′‐bpy)2]n (1), {[Mn(L)(phen)]·(MeOH)}n (2), and [Mn(L)(dipt)]n (3), (2,2′‐bpy = 2,2′‐bipyridine, phen = 1,10‐phenanthroline, and dipt = 2,9‐dimethyl‐1,10‐phenanthroline) were synthesized and characterized by single‐crystal X‐ray diffraction and analyses of their magnetic properties. 1 is a trinuclear manganese structure with a 2D motifs, which can join by hydrogen bond bridges to give 3D supramolecular architectures. 2 has a dinuclear center forming a 1D supramolecular ladder chain. The mononuclear complex 3 displays 1D metal‐organic chains driven by μ2‐L linkers. Their structural differences were investigated, revealing that the influence of steric hindrance on the structures of acid‐based coordination polymers is realized through changing the N‐heterocyclic ancillaries of diverse steric hindrance. Obviously, with decreasing of the steric hindrance of the N‐donor ligand, complexes 1–3 show structures from 1D to 2D and mononuclear to multinuclear. Magnetic susceptibility measurements indicate that 1 and 2 have dominating antiferromagnetic couplings between metal ions, whereas compound 3 is paramagnetic.

Synthesis, crystal structure and antimicrobial activity of a hetero trinuclear manganese(III)-iron(II) complex derived from N,N’-bis(5-methylsalicylidene)-1,2-diaminoethane

A new hetero trinuclear manganese(III)-iron(II) complex, [Mn(salen)(H2O)]2[Fe(CN)6], in which salen is the dianionic form of N,N’-bis(5-methylsalicylidene)-1,2-diaminoethane, has been prepared and characterized by elemental analyses, IR, and single crystal X-ray crystallographic determination. The crystal of the complex is monoclinic: space group P21/c, a = 10.768(2), b = 14.248(3), c = 15.222(3) Å, β = 95.394(2)º, V = 2325.0(8) Å3, Z = 2, R1 = 0.0754, wR2 = 0.2366. The bis-Schiff base ligand coordinates to the Mn atom through phenolate O and imine N atoms. Each Mn atom in the complex is in octahedral coordination, with the equatorial donor atoms come from the Schiff base ligand, and with the axial donor atoms come from a water O atom and a cyanide N atom. The effects of the complex on the antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans were studied. KEY WORDS: Schiff base, Manganese(III) complex, Iron(II) complex, Heteronuclear, Crystal structure Bull. Chem. Soc. Ethiop. 2015, 29(3), 407-413.DOI: http://dx.doi.org/10.4314/bcse.v29i3.8

A hetero trinuclear manganese(III)-iron(II) complex derived from N,N′-bis(5-chlorosalicylidene)-1,2-diaminoethane: Synthesis, crystal structure, and antimicrobial activity

A new hetero trinuclear manganese(III)-iron(II) complex, [Mn(ClSalen)(H2O)]2[Fe(CN)5(NO)] · CH3OH · H2O, where ClSalen is the dianionic form of N,N′-bis(5-chlorosalicylidene)-1,2-diaminoethane, has been prepared and characterized by elemental analyses, IR, and single crystal X-ray crystallographic determination (CIF file CCDC no. 1024666). The crystal of the complex is orthorhombic: space group Pca21, a = 27.784(2), b = 10.8876(6), c = 15.1755(8) A, V = 4590.5(4) A3, Z = 2, R1 = 0.0596, wR2 = 0.1406. The bis-Schiff base ligand coordinates to the Mn atom through two phenolate O and two imine N atoms. Each Mn atom in the complex is in octahedral coordination, with the equatorial donor atoms come from the Schiff base ligand, and with the axial donor atoms come from a water O atom and a cyanide N atom. The effects of the complex on the antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans were studied.

Mono-, di- and tri-nuclear manganese(II) complexes derived from a quinquedentate ligand: Superoxide dismutase and catalase mimetic studies

In this study, three manganese complexes [Mn(H2L)Cl2]·MeOH, [Mn3(L)2(OAc)2(MeOH)2]·2MeOH and [Mn2Ca(L)2(OAc)2(MeOH)2]·2MeOH derived from a quinquedentate Schiff base ligand (H2L) were synthesised and characterised by the spectroscopic and analytic methods. Molecular structures of the complexes were determined by single crystal X-ray diffraction studies. In mononuclear complex [Mn(H2L)Cl2]·MeOH, the Mn(II) ions are seven-coordinate pentagonal bipyramidal geometry with two chloride ions at the axial positions. The trinuclear complex [Mn3(L)2(OAc)2(MeOH)2]·2MeOH consists of two mononuclear units linked by a central Mn(II) ion. The calcium containing complex [Mn2Ca(L)2(OAc)2(MeOH)2]·2MeOH contains two mononuclear units bridged by a six-coordinate Ca(II) ion. The superoxide dismutase (SOD activities of the structurally complexes were evaluated and the mononuclear complex [Mn(H2L)Cl2]·MeOH showed the greatest SOD activity with an IC50 value of 0.95μM which gives a calculated kcat value of 1.67×106M−1s−1. Finally, the ability of the complexes to disproportionate H2O2 in the presence of base was tested by measuring the rate of oxygen evolution at room temperature. The trinuclear [Mn3(L)2(OAc)2(MeOH)2]·2MeOH complex is the most efficient complex catalase mimic of the tested complexes with the fastest rate 5.33ml/s.

Synthesis, Crystal Structures, and Magnetic and Catalytic Studies on a Linear Trinuclear MnII 3 Complex.

An almost linear (<Mn-Mn-Mn=132.25°) trinuclear manganese(II) complex [Mn3 (L)(N3 )4 ]⋅2 H2 O (1) of a decacoordinating N8 O2 donor ligand, H2 L, was synthesized and structurally characterized by means of single-crystal X-ray crystallography and mass spectrometry. All the MnII centers are in pseudo-octahedral geometry and wrapped by a single decacoordinating N8 O2 donor ligand. The central manganese atom (Mn2) is connected to two terminal manganese (Mn1 and Mn3) atoms by two bridging phenolate O atoms and two bridging azide N atoms. Compound 1 is the first example of a linear trinuclear model to show pronounced epoxidation of olefins by tert-butylhydroperoxide (TBHP) with a turnover number (TON) greater than 950. Though epoxidation of olefins by m-chloroperbenzoic acid (m-CPBA) was found to be complete within 20 minutes of mixing, the conversion was not more than 40 % and corresponding alcohols were found to be major products, whereas with H2 O2 as oxidant there was no visible catalytic epoxidation of olefins. Furthermore, the compound was characterized by temperature-dependent magnetic susceptibility measurements and a total spin ground state of St =15/2 was found.

Synthesis, crystal structure and magnetic properties of a trinuclear phenolate bridged manganese complex containing Mn(ii)–Mn(iii) ions

A trinuclear manganese complex containing Mn(III)–Mn(II)–Mn(III) cores, [Mn3(bp)4(CH3OH)]·0.875CH3OH·0.125H2O (1), has been prepared and structurally characterized where H2bp is an O3-donor bis(phenolate) ligand {H2bp = 2,2′-sulfinylbis(4-methylphenol)}. The combined structural and magnetic analysis reveals the mixed valence character of the compound with one central Mn(II) ion and two outer Mn(III) ions connected by phenolate bridging groups. The Mn(III)–Mn(II)–Mn(III) angle is close to a linear arrangement (∼160°) and the Mn(II)⋯Mn(III) separations are about 3.21 A. The coordination environment around the two terminal Mn(III) ions is distorted octahedral (O6) and shows Jahn–Teller elongation, while the central Mn(II) has a distorted five coordinated trigonal-bypyramidal (O5) coordination environment. In the central Mn(II) the equatorial Mn–O bond lengths are shorter than the axial Mn–O ones. The crystal packing of 1 involves hydrogen bonding between the complex and the uncoordinated methanol molecule. The analysis of the magnetic susceptibility data is consistent with ferromagnetic intramolecular coupling among the Mn(III) and the Mn(II) ions. The system can be interpreted in terms of a simple Heisenberg–Dirac–Van Vleck model H = −J(S1S2 + S2S3) with a magnetic coupling constant of J = 0.28 cm−1.

Chiral Single-Chain Magnet: Helically Stacked [MnIII2CuII] Triangles

The one-dimensional complex [Mn(III)2Cu(II)(μ3-O)(Cl-sao)3(EtOH)2]·EtOH (Mn2Cu) was obtained by the metal replacement reaction of the trinuclear manganese complex (Et3NH)[Mn(III)3(μ3-O)Cl2(Cl-sao)3(MeOH)2(H2O)2] with [Cu(acac)2]. The Mn2Cu chain exhibits single-chain-magnet behavior with finite-size effects due to its large magnetic anisotropy.

A New Two‐Dimensional Manganese(II) Coordination Polymer Constructed from Trinuclear Molecular Building Block: Syntheses, Structure and Magnetic Property

Abstract A new manganese(II) coordination polymer, [Mn3(atpt)3(2, 2′‐bpy)2]n (1) (H2atpt = 2‐aminoterephthalic acid; 2, 2′‐bpy = 2, 2′‐bipyridine), was synthesized by hydrothermal reaction of Mn(OAc)2, H2atpt, and 2, 2′‐bpy. It was structurally characterized by element analysis, IR spectroscopy, powder XRD, and magnetic measurements. X‐ray single‐crystal analysis was carried out for 1, which crystallizes in the orthorhombic system, space group Pbca. The single X‐ray diffraction studies reveal that 1 consists of infinite layers of alternating trinuclear manganese subunits and H2atpt ligands. There are two types of different coordination modes of H2atpt in 1. Magnetic susceptibility data for 1 were measured in the range 3–300 K. There are antiferromagnetic interactions between manganese ions of 1.