MnII Ions Research Articles

Magnetoelectric Coupling in a Mn4Na-Organic Complex under Pulsed Magnetic Fields up to 73 T.

Research on the magnetoelectric (ME) effect (or spin-electric coupling) in molecule-based magnetic materials is a relatively nascent but promising topic. Molecule-based magnetic materials have diverse magnetic functionalities that can be coupled to electrical properties. Here we investigate a realization of ME coupling that is fundamental but not heavily studied─the coupling of magnetic spin level crossings to changes in electric polarization. A mixed-valence Mn4Na complex with a total ground-state spin S = 5/2 under zero magnetic field and S = 17/2 under high magnetic field undergoes a cascade of ground-state level crossings of the Sz states with increasing magnetic field. Magnetization and electrical polarization measurements under pulsed magnetic fields up to 73 T show that each spin level crossing is accompanied by a significant change in electric polarization that is an even function of the applied magnetic field. A molecular Hamiltonian describing antiferromagnetic exchange in a distorted tetrahedron of three MnIII and one MnII ions matches the data well. We conclude that the ME coupling is caused by magnetostriction within the polar molecule as it distorts to lower its magnetic exchange energy.

Reversible Single-Crystal to Single-Crystal Transformation and Associated Magnetism of a Cyanide-Bridged Chiral-Structured Magnet.

A chiral molecule-based magnet [MnII (S-pnH) (H2O)][MnIII(CN)6]·H2O (S-pn = S-1,2-diaminopropane), 1S·2H2O (P212121), has been obtained, which has a two-dimensional (2D) square network of cyanide-bridged MnII-MnIII ions. The crystallographic research on this coordination polymer indicates that it is robust enough to transform the single-crystal structure upon dehydration as well as rehydration. Meanwhile, the magnetic property changes are reversibly associated with the structural phase transitions. The complete reversibility upon dehydration/rehydration was demonstrated using in situ X-ray diffraction from the as-prepared 1S·2H2O to the dehydrated [MnII (S-pnH)][MnIII(CN)6], 1S, then rehydrated to [MnII (S-pnH) (H2O)][MnIII(CN)6]·H2O, 1S-HP, and dehydrated again to [MnII (S-pnH)][MnIII(CN)6], 1S-DeHP. Neither the space groups nor the crystal axes changed during the dehydration/rehydration process. The dehydration is considered to be associated with a change in the coordination of the S-pnH from one 2D layer to the neighboring one involving a proton transfer and is accompanied by new cyanide bridging of MnII and MnIII ions formed between the 2D sheet. Corresponding to the 2D to three-dimensional (3D) structural transition, the study of magnetic properties reveals that the Curie temperature of long-range magnetic ordering for 1S (TC = 45 K) is more than double that for 1S·2H2O (TC = 21 K).

An insight into the utilization of high-sulfur green Saudi Arabian petcoke as an ecofriendly sorbent for enhanced simultaneous sequestration of heavy metal ions from industrial wastewaters

Developing effective and green sorbents for the sequestration of water pollutants has increased attention to safe and sustainable water generation. This study aimed to discover a new utilization and the ability of green, high-sulfur Saudi Arabian petcoke (SA-PET) for heavy metal ion uptake. The organic sulfur content and aromatic properties of SA-PET allowed for rapid and improved performance against various metal ions via strong complex formation reactions and cation-π interactions. Also, the effects of different analytical factors were carefully studied and optimized. At pH 6–7, the maximum recovery values of PbII, CuII, CdII, ZnII, MnII, NiII and CoII metal ions were 21.09–95.76%. The experimental results demonstrate single-layer adsorption at the binding sites on the petcoke’s surface, and they are in good agreement with the Langmuir model in explaining the adsorption process, which is driven by electrostatic interactions between the petcoke surface and the studied metal ions. The pseudo-second-order kinetics model fits the adsorption data for all the target metal ions well. Furthermore, the outstanding SA-PET's stability allowed for efficient extractions over the course of 10 successive runs with negligible loss in the metal recovery percentage. With extraction recoveries up to 96.6% and a relative standard deviation less than 5%, SA-PET's efficiency in removing the target metal ions from different industrial wastewater samples gives it excellent promise as a novel green sorbent for detoxifying heavy metals from aquatic life. In conclusions, our findings, SA-PET emerged as a viable substitute for traditional synthetic adsorbents of heavy metals, in keeping with the growing trend toward green adsorbents for more sustainable development.

(2,5-Di-methyl-imidazole){N,N',N'',N'''-[porphyrin-5,10,15,20-tetra-yltetra-(2,1-phenyl-ene)]tetra-kis(pyridine-3-carboxamide)}manganese(II) chloro-benzene disolvate.

In the title compound, [Mn(C68H44N12O4)(C5H8N2)]·2C6H5Cl, the central MnII ion is coordinated by four pyrrole N atoms of the porphyrin core in the basal sites and one N atom of the 2,5-di-methyl-imidazole ligand in the apical site. Two chloro-benzene solvent mol-ecules are also present in the asymmetric unit. Due to the apical imidazole ligand, the Mn atom is displaced out of the 24-atom porphyrin mean plane by 0.66 Å. The average Mn-Np (p = porphyrin) bond length is 2.143 (8) Å, and the axial Mn-NIm (Im = 2,5-di-methyl-imidazole) bond length is 2.171 (8) Å. The structure displays inter-molecular and intra-molecular N-H⋯O, N-H⋯N, C-H⋯O and C-H⋯N hydrogen bonding. The crystal studied was refined as a two-component inversion twin.

Synthesis, crystal structure and Hirshfeld surface analysis of Mn(II) coordination compounds with ONO-donor ligands derived from ampyrone

Four manganese(II) coordination compounds, [Mn2(L1)2(NCS)2(MeOH)2] (1) [Mn(HL2)2(NCS)2(MeOH)2] (2) [Mn2(L3)2(NCS)2(MeOH)2] (3) and [Mn(HL3)2(NCS)2(MeOH)2] (4) have been synthesized from the reaction of MnCl2·4H2O, KSCN and Schiff base ligands derived from 4-aminoantipyrine (HL1= (E)-4-((2-hydroxybenzylidene)amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one; HL2 = (E)-4-((2-hydroxy-3-methoxybenzylidene)amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one and HL3 = (E)-4-((5-bromo-2-hydroxybenzylidene)amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one) in methanol and the products have been characterized with single crystal X-ray diffraction (SC-XRD). The detailed studies involve the synthesis, crystal structure, FT-IR spectroscopy, UV–Vis spectroscopy, bond sum valence calculations, elemental and Hirshfeld surface analyses. In the case of 1 and 3, the phenolate bridged dinuclear MnII complexes are formed by chelating two Schiff base ligands, two thiocyanates and two methanol molecules and two crystallographically equivalent MnII ions are connected together by phenolate oxygen with the Mn···Mn distance of 3.1618(4) (in 1) and 3.1910(6) Å (in 3). In the case of 2 and 4, the octahedral coordination geometry of the MnII center in these mononuclear species is formed by chelating two Schiff base ligands, two thiocyanates and two methanol molecules. The presence of intermolecular hydrogen bond in 2 leads to the formation of molecular chains within the layers. Also, the presence of efficient π···π interactions between pyrazolone and phenyl rings and intermolecular hydrogen bonding in 4 lead to the formation of molecular chains within the layers. All of the intermolecular and intramolecular interactions have been studied by Hirshfeld surface analyses.

Assembly of MnIII ions into di-, tetra-, deca-nuclear coordination complexes, zero- to three-dimensional molecular frameworks: molecular spin flop to and short-range bulk magnetic spin flop ordering

Octahedral MnIII ions possess significant magnetic anisotropy due to second-order orbital contribution combined with Jahn–Teller distortion.

Rare Nuclearities and Unprecedented Structural Motifs in Manganese Cluster Chemistry from the Combined Use of Di-2-Pyridyl Ketone with Selected Diols

The combined use of di-2-pyridyl ketone ((py)2CO) with various diols in Mn cluster chemistry has afforded five new compounds, namely, [Mn11O2(OH)2{(py)2CO2}5(pd)(MeCO2)3(N3)3(NO3)2(DMF)4](NO3)∙2DMF∙H2O (1∙2DMF∙H2O), [Mn11O2(OH)2{(py)2CO2}5(mpd)(MeCO2)3(N3)3(NO3)2(DMF)4](NO3) (2), [Mn12O4(OH)2{(py)2CO2}4(mpd)2(Me3CCO2)4(NO3)4(H2O)6](NO3)2∙2MeCN (3∙2MeCN), [Mn4(OMe)2{(py)2C(OMe)O}2(2-hp)2(NO3)2(DMF)2] (4), and [Mn7{(py)2CO2}4(2-hp)4(NO3)2(DMF)2](ClO4)∙DMF (5∙DMF) ((py)2CO22− and (py)2C(OMe)O− = gem-diol and hemiketal derivatives of di-2-pyridyl ketone, pdH2 = 1,3-propanediol, mpdH2 = 2-metly-1,3-propanediol, 2-hpH2 = 2-(hydroxymethyl)phenol). Complexes 1 and 2 are isostructural, possessing an asymmetric [MnIII5MnII6(μ4-O)(μ3-O)(μ3-OH)(μ-OH)(μ3-OR)2(μ-OR)10(μ-N3)]8+ core. Compound 3 is based on a multilayer [MnIII8MnII4(μ4-O)2(μ3-O)2(μ3-OH)2(μ-OR)12]10+ core, while complex 4 comprises a defective dicubane core. The crystal structure of 5 reveals that it is based on an unusual non-planar [MnIII5MnII2(μ-OR)12]7+ core with a serpentine-like topology. Direct current (dc) magnetic susceptibility studies revealed the presence of dominant antiferromagnetic exchange interactions in complex 3, while ferromagnetic coupling between the Mn ions was detected in the case of compound 5. Fitting of the magnetic data for complex 4 revealed weak antiferromagnetic interactions along the peripheral MnII∙∙∙MnIII ions (Jwb = −0.33 (1) cm−1) and ferromagnetic interactions between the central MnIII∙∙∙MnIII ions (Jbb = 6.28 (1) cm−1).

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).

Molecular structure, as well as optical and magnetic properties, of coordination complexes comprising the organic dye flavanthrone with transition metals (MnII, CrIII, CrIV) and lanthanides (DyIII, GdIII)

The reduction of the organic dye flavanthrone (Vat Yellow 1) to the dianion state in the presence of metal-containing compounds yields coordination complexes in which two metal fragments coordinate to flavanthrone dianions to form short M − O bonds. Flavanthrone dianion coordinates to two manganese(II) acetylacetonate units in {flavanthrone⋅[MnII(acac)2]2}2− (1) with an average Mn–O bond length of 2.048(3) Å. Two dysprosium(III) or gadolinium(III) 2,2,6,6-tetramethyl-3,5-heptanedionate (TMHD) units form longer M − O bonds in {cryptand(Cs+)}2{flavanthrone⋅[DyIII(TMHD)3]2}2− (2) and {cryptand(K+)}2{flavanthrone⋅[GdIII(TMHD)3]2}2−⋅2C6H4Cl2⋅ 2C6H14 (3), with bond lengths of 2.192(2) and 2.241(4) Å, respectively. Furthermore, the utilization of decamethylchromocene as a reductant yields the unusual neutral {(flavanthrone2−)⋅[Cp*CrIII(acac)]2} comprising acac anion (4) and {(flavanthrone2−)⋅[Cp*CrIVCl2]2} comprising two chloride anions (5). Both have zwitter-ionic nature in which negative charge of flavanthrone dianions is compensated by chromium countercations. They coordinate to two chromium-containing units with short Cr–O bonds of 1.937(2) and 1.962(5) Å, respectively. The formation of flavanthrone dianions in 1–5 is confirmed by their optical spectra, the disappearance of the bands corresponding to the C=O vibrations in the infrared spectra of the complexes, and the elongation of the carbon–oxygen bonds during the formation of 1–5. The formation of binuclear, paramagnetic species with the flavanthrone dianions induces weak antiferromagnetic couplings between the paramagnetic centers because the flavanthrone dianions are diamagnetic. Stronger couplings with exchange parameters of −0.44 and −0.55 cm−1 were observed for the chromium ions bearing the shortest M − O bonds for 5 and 4, respectively. Conversely, MnII and lanthanides (GdIII, DyIII) comprising longer M − O bonds exhibit smaller J values (close to zero in 3 or equal to −0.026 and −0.05 cm−1 in 2 and 1, respectively). The complexes comprising MnII, GdIII, and CrIII display electron paramagnetic resonance (EPR) signals. The signal from MnII is approximated considering that the exchange interaction between the two MnII ions is −0.05 cm−1. Well resolved zero-field splitting (ZFS) is displayed; it facilitates the determination of the positive ZFS parameter, D, of +0.83 cm−1 and the unusually high E value, +0.62 cm−1. The spectrum of 3 comprising two GdIII ions containing 12 lines was approximated with D and E values of −0.083 and −0.021 cm−1, respectively. The odd-spin CrIII (S = 3/2) display a broad, asymmetric EPR signal at g = 3.77 without ZFS, whereas the even-spin CrIV is EPR-silent. Taken together, this study reveals that the dianions of organic dyes represent promising bidentate ligands for preparing coordination complexes with paramagnetic d- and f-block metal ions.

Creation of a Tetranuclear MnIII2MnII2 Metalloring Structure Supported by a Penicillamine-Derived Schiff-Base Ligand

Abstract The reaction of a Schiff-base ligand derived from 5-chloro-salicylaldehyde and d-penicillamine with MnIII ions in the presence of nBu3N produced a disulfide-bridged tetranuclear MnIII2MnII2 metalloring structure through thiolate oxidation. The corresponding treatment using Et3N instead of nBu3N gave a giant 13-nuclear MnIII6MnII7 structure.

Magnetic coupling of divalent metal centers in postsynthetic metal exchanged bimetallic DUT-49 MOFs by EPR spectroscopy

EPR measurements at X- (9.5 GHz), Q- (34 GHz) and W-band (94 GHz) on paddlewheel (PW) type post-synthetic metal exchanged DUT-49(M,M): M- Zn, Mn, Cu MOFs are here reported (DUT–Dresden University of Technology). Temperature-dependent X-band measurements are recorded from T = 7 K to T = 170 K on monometallic DUT-49(Cu), DUT-49(Mn), and bimetallic DUT-49(Cu0.7Zn0.3), DUT-49(Cu0.5Mn0.5) MOFs. In the case of the CuII - CuII dimers in DUT-49(Cu), an isotropic exchange coupling of the metal ions (2J = −240(11) cm−1) determined from the EPR intensity of the S = 1 spin state of the CuII–CuII dimers using the Bleaney Blowers equation. The sign of the found isotropic exchange coupling constant confirms an antiferromagnetic coupling between the cupric ions. Also, the MnII ions in the paddle wheels of DUT-49(Mn) are antiferromagnetically coupled. However, at low temperatures, EPR measurements reveal the presence of CuII and MnII monomers in DUT-49(Cu) and DUT-49(Mn), respectively, either associated with extra framework sites or defective paddle wheels. Otherwise, EPR signals observed for bimetallic DUT-49(Cu0.7Zn0.3) and DUT-49(Cu0.5Mn0.5) MOFs reveal the formation of mixed ion CuII–ZnII and CuII–MnII paddle wheels with SCuZn =1/2 and SCuMn = 2 spin states, respectively.

Manganese(ii) complexes of hexaazatrinaphthylene and hexaazatrianthracene: synthesis, structure and properties

A series of complexes containing dianionic and radical-trianionic hexaazatriphenylene (HATNA) and hexazatrianthracene (HATA) ligands and high-spin MnII ions (S = 5/2) were obtained. It is shown that elongation of the Mn–N bonds results in a decrease of both Mn–ligand and Mn–Mn couplings.

Double dicyanamide decorated double phenoxide bridged MnIII dimer with single-molecule magnetic behaviour and bio-catalytic activity

Herein, we report the magnetic properties and bio-catalytic activity of a flying bee-like double phenoxido bridged dinuclear MnIII-Schiff base complex decorated with double dicyanamide (dca−) ligands and formulated as: [Mn2(L)2(dca)2] (1) (where H2L = 2,2′-((1E,1′E)-(ethane-1,2-diylbis(azanylylidene))-bis(ethan-1-yl-ylidene))diphenol). The complex has been synthesised by one-pot stepwise reaction of the tetradentate Schiff’s base ligand H2L with MnCl2 and dca− at 1:1:2 ratio under aerobic conditions. It has been characterized by single crystal X-ray diffraction (SC-XRD) and spectroscopic techniques. Complex 1 contains two MnIII ions connected by a double phenoxido bridge in an octahedral geometry and terminal dca− ligands. The dimers are connected to other dimers through both hydrogen bonding and π-interactions to form an extended supramolecular network. The present study reveals that in presence of tetradentate Schiff base ligands, the use of a 1:2 Mn:dca− ratio leads to formation of a dimeric MnIII complex in contrast to the discrete mononuclear complexes or 1D structures previously obtained for the Mn:dca− ratio of 1:1. The magnetic study indicates that the dimeric MnIII complex shows a negligible MnIII–MnIII interaction and a large anisotropy. The AC susceptibility measurements indicate that complex 1 behaves as a field-induced single-molecule magnet (SMM), with a high energy barrier of 73(4)K. The study of model catechol oxidase-like enzyme activity of complex 1 indicates that the dimeric MnIII complex acts as an active catalyst (kcat = 34.94 h−1) in the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) in presence of aerial O2 in acetonitrile medium.

Synergistic Effect of FeII and MnII Ions in Cyano-Bridged Heterometallic Coordination Polymers on Catalytic Selectivity of Benzene Oxygenation to Phenol

A cyano-bridged heterometallic coordination polymer with partial deficiencies of CN- ligands, [MnII(H2O)8/3]3/2[FeII(CN)5(NH3)], forms open metal sites both on MnII and FeII ions by liberation of monodentate ligands such as NH3 and H2O. [MnII(H2O)8/3]3/2[FeII(CN)5(NH3)] exhibits high catalytic activity and selectivity of benzene oxygenation to phenol in the presence of m-chloroperoxybenzoic acid as an oxidant. The postcatalytic spectroscopy of [MnII(H2O)8/3]3/2[FeII(CN)5(NH3)] and catalysis comparison with a physical mixture of [MnII(H2O)3]2[FeII(CN)6] and [Fe(H2O)3/2]4/3[Fe(CN)6], which has open metal sites on both MnII and Fe ions separately, indicated that the high activity resulted from high oxidation ability and phenol adsorption ability of FeII and MnII ions, respectively.

Very Anisotropic 2D Molecular Magnetic Materials Based on Pentagonal Bipyramidal Heptacyanidorhenate(IV).

The first neutral 2D heterometallic assemblies based on orbitally degenerate heptacyanidorhenate(IV) were prepared and structurally characterized. An analysis of the magnetic data for the polycrystalline samples of Ph4P[{Mn(acacen)}2Re(CN)7]·Solv (1) and PPN[{Mn(acacen)}2Re(CN)7]·Solv (2) have shown that both materials display slow magnetic relaxation at temperatures below 10 and 21 K for 1 and 2, respectively. Despite the presence of the same molecular magnetic modules that make up the anionic layers, the studied 2D networks differ significantly in magnetic anisotropy, having a small coercive field (0.115 T) for 1 and a large one (~2.5 T) for 2 at 2 K. In addition, for both polymers a M(H) value does not saturate at the maximum available field of 7 T, and the material 2 is a metamagnet. This intriguing difference originates from the cooperative anisotropic spin interaction in ReIV-CN-MnIII pairs and the zero field splitting (ZFS) effect of MnIII ions with a noncollinear alignment of the local magnetic axes in crystals of the compounds.

Crystal structure of a heterotrimetallic 12-metallacrown-4 with 2-propylvalerate anion bridges

The synthesis and single-crystal X-ray structure for tetraaquatetrakis(μ-2-propylvalerato)tetrakis(μ4-salicylhydroximato)dysprosiumtetramanganesesodium dimethylformamide tetrasolvate, [DyMn4Na(C7H4NO3)4(C8H15O2)4(H2O)4]·4C3H7NO or DyNa(2-PV)4[12-MCMnIII Nshi-4](H2O)4·4DMF, 1, where MC is metallacrown, shi3− is salicylhydroximate, 2-PV is 2-propylvalerate, and DMF is N,N-dimethylformamide, is reported. The slightly domed metallamacrocycle contains four ring MnIII ions and four shi3− ligands that generate an [MnIII—N—O] repeat unit that recurs four times. The ring MnIII ions are five-coordinate with a square-pyramidal shape. Furthermore, the metallacrown binds both a DyIII ion and a Na+ ion in the central cavity. The central ions are located on opposite faces of the cavity with the DyIII ion located on the convex side of the MC and the Na+ ion located on the concave side. Each central ion is eight-coordinate although they possess different geometries. The DyIII ion has a square-antiprismatic shape, while the Na+ ion has an extremely distorted biaugmented trigonal–prismatic shape. The four 2-propylvalerate anions help to tether the DyIII to the MC cavity by forming bridges between the DyIII ion and each ring MnIII ion. Moreover, the interstitial DMF molecules are hydrogen bonded to the water molecules that complete the coordination environment of the Na+ ion. The metallacrown framework (excluding the DyIII and Na+ ions), the bridging 2-propylvalerate, and the interstitial DMF molecule experience whole-molecule disorder due to the rotational orientation of the metallamacrocycle. Additionally, the main moiety alkyl chain of the 2-propylvalerate is disordered over two additional orientations, and the main moiety interstitial DMF molecule is disordered over one additional orientation. The main moiety of the metallacrown framework refined to 0.9030 (14), while the minor B-moiety refined to 0.0971 (14). The main moiety alkyl chain of the 2-propylvalerate refined to 0.287 (3): 0.309 (3): 0.307 (3), and the minor B-moiety alkyl chain refined to 0.0971 (14). Lastly, the main moiety interstitial DMF refined to 0.549 (3): 0.354 (3), and the minor B-moiety DMF refined to 0.0971 (14).

Ligands-triggered evolution of catalytic intermediates during periodate activation via soluble Mn(II) for organic contaminants’ abatement

Homogenous catalysis technology could be flexibly combined with existing water treatment facilities, which presents broad applicational prospects and deserves systematic study. This work reinvestigated the periodate (IO4−, PI) activation process mediated by hydrated MnII ions and highlighted the critical involvement of the in-situ formed colloidal MnO2 (MnIV). MnII ions were directly oxidized to colloidal MnIV in the MnII/PI system, and the nascent MnIV could in turn activate PI to form MnIV-PI* complex as the reactive oxidant. Besides, several kinds of ligands were introduced into the MnII/PI oxidation system to explore their influences. Nitrilotriacetic acid (NTA) outperformed other selected ligands and could significantly enhance PI activation to degrade organic contaminants, which could achieve a removal efficiency of ∼99% within seconds. Interestingly, the presence of NTA completely altered the catalytic pathways rather than just accelerating the generation of reactive oxidants. Combining the results of sulfoxide-probe transformation tests and the 18O isotope-tracer experiments, we proposed that the high-valent manganese-oxo (MnV-oxo) species was the dominant reactive oxidant generated in the MnII/NTA/PI system, and the metastable MnIII complex was the precursor of the MnV-oxo species. Notably, maintaining the MnII high-spin d5 center and stabilizing the in-situ formed MnIII intermediates were the crucial premises for the evolution of the catalytic oxidation process triggered by functional ligands. This work clarified the critical involvement of functional ligands during PI activation via soluble MnII and might also inspire the designing of heterogeneous catalyst modification for the water treatment technology.

Against the Norm: Non Irving-Williams Transmetalation in Transition Metal Dimers.

We report the synthesis and characterization of three dinuclear 3d3d' complexes, CuCu (), MnMn (), and CuMn ([CuIIMnIIL(NO3)2]), that utilize the ligand, H2L (6,6'-dimethoxy-2,2'-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol). The relative stabilities of these complexes were investigated using experimental and computational techniques, revealing a non-Irving-Williams transmetalation, whereby a MnII ion can displace a CuII ion from its binding pocket in CuCu to yield the more stable CuMn complex. Magnetic characterization of the reported complexes revealed an unexpected ferromagnetic coupling between the two CuII ions of CuCu with J = +63.0 cm-1.

Constructing "Closed" and "Open" {Mn8} Clusters.

Use of the 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane ligand, LH3, in manganese chemistry affords access to two structurally related {Mn8} clusters: a “closed” {MnIII6MnII2} puckered square wheel of formula [Mn8L2(LH)O3(OH)2(MeO)2Br(imH)(H2O)3](Br)3 (1; imH = imidazole) and an “open” {MnIII8} rod of formula [MnΙΙΙ8L2O4(aibH)2(aib)2(MeO)6(MeOH)2](NO3)2 (2, aibH = 2-amino-isobutyric acid). In each case the triaza ligands, L/LH, direct the formation of {Mn3} triangles with their N atoms preferentially bonding to the Jahn–Teller axes of the MnIII ions. Subsequent self-assembly is dependent on the anion of the Mn salt and the identity of the organic coligand employed—the terminally bonded imidazole and the chelating/bridging amino acid. The {Mn3} triangles fold up on themselves in 1, forming a wheel. However, the syn, syn-bridging carboxylates in 2 prevent this from happening, instead directing the formation of a linear rod. Magnetic susceptibility and magnetization measurements reveal competing ferro- and antiferromagnetic interactions in both complexes, the exchange being somewhat weaker in 1 due to the presence of MnII ions.

Mixed‐Ligand Metal‐Organic Frameworks: Synthesis and Characterization of New MOFs Containing Pyridine‐2,6‐dimethanolate and Benzene‐1,4‐dicarboxylate Ligands

AbstractThe development of synthetic approaches towards new mixed‐ligand metal organic frameworks (MOFs) has been attracting considerable attention recently as they display fascinating properties due to the synergistic effect between the different ligands. Herein, the initial combination of pyridine‐2,6‐dimethanol (H2pdm) with benzene‐1,4‐dicarboxylic acid (H2bdc) has provided access to three new mixed‐ligand MOFs, [M3(bdc)2(Hpdm)2]n (MII=ZnII, 1; MnII, 2) and [Mn3(bdc)3(H2pdm)2]n (3). 1–3 are the first MOFs containing H2pdm in its neutral or anionic form. 1 and 2 are isostructural 2D MOFs with a square lattice (sql) framework topology, while 3 is a 3D MOF possessing a primitive cubic (pcu) topology. Dc magnetic susceptibility measurements for 3 demonstrate antiferromagnetic interactions between the MnII ions which is a combination of intra‐ and intertrimer exchange pathways.