Mononuclear Mn Research Articles

Thermal Jahn-Teller Distortion Changes and Slow Relaxation of Magnetization in Mn(III) Schiff Base Complexes.

The impact that the anion and alkyl group has on the electronic structures and magnetic properties of four mononuclear Mn(III) complexes is explored in [Mn(salEen-Br)2]Y (salEen-Br = 2-{[2-(ethylamino)ethylimino]methyl}-4-Br-phenol; Y = ClO4- 1 and BF4-·1/3CH2Cl2 2) and [Mn(salBzen-Br)2]Y (salBzen-Br = 2-{[2-(benzylamino)ethylimino]methyl}-4-Br-phenol; Y = ClO4- 3 and BF4- 4). X-ray structures of [Mn(salEen-Br)2]ClO4·0.45C6H14 1-hexane, [Mn(salEen-Br)2]BF4·0.33CH2Cl2·0.15C6H14 2-dcm-hexane, and 3-4 reveal that they crystallize in ambient conditions in the monoclinic P21/c space group. Lowering the temperature, 2-dcm-hexane uniquely exhibits a structural phase transition toward a monoclinic P21/n crystal structure determined at 100 K with the unit cell trebling in size. Remarkably, at room temperature, the axially elongated Jahn-Teller axis in 2-dcm-hexane is poorly defined but becomes clearer at low temperature after the phase transition. Magnetic susceptibility measurements of 1-4 reveal that only 3 and 4 show slow relaxation of magnetization with Δeff/kB = 27.9 and 20.7 K, implying that the benzyl group is important for observing single-molecule magnet (SMM) properties. Theoretical calculations demonstrate that the alkyl group subtly influences the orbital levels and therefore very likely the observed SMM properties.

Mononuclear Mn(III) complex with a terminal azide supported by phenol-based tetradentate N2O2 donor ligand: Synthesis, structure, properties, and catechol oxidase activity

Mixed ligand octahedral Mn(III) complex [Mn(L)(CH3OH)(N3)] (1) with sterically constrained phenol-based tetradentate N2O2 ligand, N,Nʹ-dimethyl-N,Nʹ-bis (2-hydroxy-3,5-dichlorobenzyl)-ethylenediamine (H2L) in association with azide ion and methanol as ancillary ligand has been synthesized. Synthesis, structure, properties, and catecholase activity of the mononuclear manganese complex (1) are described. Complex (1) crystallizes in triclinic space group P-1 with a = 10.5431(5) Å, b = 11.3731(6) Å and c = 22.9638(12) Å. The crystal structure reveals that complex (1) is an Mn (III) complex with flexible phenol-based ligand in association with azide as a terminal monodentate ligand. Electrochemical study of the mononuclear manganese complex (1) gives two quasi reversible oxidation peaks (E11/2≈ 0.18 V and E21/2≈ 0.23 V) in the positive potential range versus Ag/AgCl reference in acetonitrile due to ligand centered phenolate/phenoxyl couple. Complex (1) shows a strong emission band at 440 nm. The complex exhibits catechol oxidase activity in methanol. Oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone in methanol has been accelerated in presence of reported manganese complex (1) with a high Kcat value of 1.43 × 104h−1.

Electrocatalytic hydrogen evolution at carbon paste electrodes doped with a manganese(II) imidazoledicarboxylate complex

Abstract A mononuclear Mn(II) complex [Mn(p-MOPhH2IDC)2(H2O)2]·2(DMF), was synthesized by the reaction of p-MOPhH3IDC (2-(4-methoxyphenyl)-1H-imidazole-4,5-dicarboxylic acid) and Mn(CH3COO)2·4H2O under solvothermal conditions and characterized by single-crystal X-ray diffraction, elemental analysis, IR and UV–vis spectroscopy. The structure analysis revealed that the manganese(II) center has a six-coordinated octahedral coordination geometry. The performance of a Mn(II) complex-doped carbon paste electrode (Mn-CPE) in the electrocatalytic hydrogen evolution reaction (HER) was evaluated by linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) methods. The polarization curve shows that the η 10 298K (overpotential, 10 mA cm−2) of the Mn-CPE was positively shifted by 341 mV compared with the bare CPE (without complex). The Tafel slope of the Mn-CPE was 161 mV dec−1. These data indicate that the Mn-CPE was effective in the HER electrocatalytic reaction. For EIS experiments, the arc diameter of the high-frequency region of the Mn-CPE was much smaller than that of the bare CPE, which further indicates the effective catalytic capacity of the Mn(II) complex for hydrogen evolution. The information obtained from this study will help to expand the application of Mn(II) complexes in the field of electrochemistry.

Synthesis, spectroscopic characterization, crystal structure, DFT and Hirschfeld surface analysis of a manganese(I) complex ([Mn(P-NH-NH-P)(CO)2][BPh4

We report the synthesis of a new Mn—PNNP complex ([Mn(P-NH-NH-P)(CO)2][BPh4]) with an original approach for the synthesis of a previously reported PNNP ligand PPh2(o-C6H4)NHCH2CH2NH(o-C6H4)PPh2 using a new protocol in a less toxic solvent. The PNNP ligand forms a stable mononuclear Mn(I) complex in a low spin state with the additional coordination of two carbonyl groups. This new complex has been characterized by elemental analysis, 1H, 13C and 31P NMR spectroscopy, FTIR spectroscopy and HRMS studies. The molecular structure of the complex was determined by X—ray diffraction analysis, which confirmed its distorted octahedral geometry with the linear tetradentate ligand in a rare cis-α-configuration. Additionally, theoretical calculations were performed on the optimized structure of the complex using the functional-basis-set combination B3PW91/6―311++G (d, p)/SDD which showed good correlation with the experimental data. The frontier molecular orbital analysis revealed a large HOMO to LUMO gap (4.66 eV) as expected for a low spin, d6 octahedral metal complex with the HOMO concentrated on the Mn centre. The Hirschfeld surface analysis signalled the important intermolecular H…H and C…H interactions. A preliminary catalytic study of the complex on transfer hydrogenation of acetophenone was conducted.

Effect of solvent and auxiliary ligand on catecholase activities of Mn(III) complexes: A comparative study

A mononuclear Mn(III) complex with composition [MnIIIL(Cl)] (1) has been utilized to prepare two new complexes, [MnIIIL(N3)(CH3OH)] (2) and [MnIIIL(μ1,3-NCS)]n (3), by substitution of the auxiliary ligand. The ligand utilized for preparation of 1 is a Schiff base (H2L), obtained by 2:1 condensation of 3-Chlorosalicylaldehyde and ethylene diamine in methanol. The chloride anion, present in the coordination sphere of the central metal ion in 1 has been replaced by two other auxiliary ligands, azide and thiocyanate, in 2 and 3, respectively. All of the three complexes behaved as bio-functional models of catechol oxidase toward oxidation of 3,5-di-tert butyl catechol (3,5-DTBC). A detailed kinetic investigations were carried out for 2 and 3 in methanol, acetonitrile and N,N′-Dimethyl formamide (DMF) separately and the corresponding turn-over numbers have been determined. The ESI-MS spectra of the substrate-catalyst mixtures in acetonitrile and methanol confirmed formation of catecholate bound Mn(III) intermediate in the mass spectral time scale. The progress of the catechol oxidation was monitored by 1H-NMR spectroscopy with the reaction mixtures containing complex-substrate ratio at 1:20 after stirring in acetonitrile as well as methanol at room temperature in open air. NMR spectral data confirmed completion of the process in 90 minutes and 45 minutes for 2 and 3, respectively. Notably, in absence of any of these complexes, aerobic oxidation of 3,5-DTBC to the corresponding quinone is negligible even after twenty four hours of mixing in the same solvent. This observation is a clear indicative of high catalytic efficiencies of the prepared complexes.

Two Novel Schiff Base Manganese Complexes as Bifunctional Electrocatalysts for CO2 Reduction and Water Oxidation.

One mononuclear Mn(III) complex [MnIIIL(H2O)(MeCN)](ClO4) (1) and one hetero-binuclear complex [(CuIILMnII(H2O)3)(CuIIL)2](ClO4)2·CH3OH (2) have been synthesized with the Schiff base ligand (H2L = N,N'-bis(3-methoxysalicylidene)-1,2-phenylenediamine). Single crystal X-ray structural analysis manifests that the Mn(III) ion in 1 has an octahedral coordination structure, whereas the Mn(II) ion in 2 possesses a trigonal bipyramidal configuration and the Cu(II) ion in 2 is four-coordinated with a square-planar geometry. Electrochimerical catalytic investigation demonstrates that the two complexes can electrochemically catalyze water oxidation and CO2 reduction simultaneously. The coordination environments of the Mn(III), Mn(II), and Cu(II) ions in 1 and 2 were provided by the Schiff base ligand (L) and labile solvent molecules. The coordinately unsaturated environment of the Cu(II) center in 2 can perfectly facilitate the catalytic performance of 2. Complexes 1 and 2 display that the over potentials for water oxidation are 728 mV and 216 mV, faradaic efficiencies (FEs) are 88% and 92%, respectively, as well as the turnover frequency (TOF) values for the catalytic reduction of CO2 to CO are 0.38 s-1 at -1.65 V and 15.97 s-1 at -1.60 V, respectively. Complex 2 shows much better catalytic performance for both water oxidation and CO2 reduction than that of complex 1, which could be owing to a structural reason which is attributed to the synergistic catalytic action of the neighboring Mn(III) and Cu(II) active sites in 2. Complexes 1 and 2 are the first two compounds coordinated with Schiff base ligand for both water oxidation and CO2 reduction. The finding in this work can offer significant inspiration for the future development of electrocatalysis in this area.

Structural elucidation of a Mn(III) derivative anchored with a tetradentate Schiff base precursor: in vitro cytotoxicity study

A new mononuclear Mn(III) derivative, [Mn(L)(H2O)2]ClO4 (1) was obtained by reacting manganese perchlorate with the tetradentate Schiff base precursor, H2L, [where H2L=C6H3(OMe)(OH)CH=N(CH2)3N=CH(OH)(OMe)C6H3] and characterized by various spectral techniques. Single crystal X-ray diffraction analysis revealed that in 1, the central Mn atom is hexa-coordinated via the NNOO donor sites of the Schiff base precursor and two water molecules, yielding a distorted octahedral geometry. Also, the EPR spectra of 1 were recorded at the solid state by varying the temperature (from 90 to 300 K) as well as in different organic solvents; DMSO, MeOH and a mixture CH2Cl2/toluene; the results obtained agree with the geometrical environment around the metal. The cytotoxic activity of the Mn(III) derivative was evaluated against normal and cancer cell lines. The derivative exhibited comparatively better cytotoxic activity against MCF-7 cells compared to SiHa and fibroblast cells.

Slow magnetic relaxation in two mononuclear Mn(II) complexes not governed by the over-barrier Orbach process.

Two hexacoordinate Mn(II) complexes containing a chelating residue of hexafluoroacetylacetone and (Cl-substituted) 4-benzylpyridine show DC magnetic functions typical for S = 5/2 spin systems: g ∼ 2, D - small. The AC susceptibility confirms a field supported slow magnetic relaxation in which the over-barrier Orbach relaxation process does not play a role. Both systems possess two or three slow relaxation channels.

HAA by the first {Mn(iii)OH} complex with all O-donor ligands.

There is considerable interest in MnOHx moieties, particularly in the stepwise changes in those O-H bonds in tandem with Mn oxidation state changes. The reactivity of aquo-derived ligands, {MOHx}, is also heavily influenced by the electronic character of the other ligands. Despite the prevalence of oxygen coordination in biological systems, preparation of mononuclear Mn complexes of this type with all O-donors is rare. Herein, we report several Mn complexes with perfluoropinacolate (pinF)2- including the first example of a crystallographically characterized mononuclear {Mn(iii)OH} with all O-donors, K2[Mn(OH)(pinF)2], 3. Complex 3 is prepared via deprotonation of K[Mn(OH2)(pinF)2], 1, the pKa of which is estimated to be 18.3 ± 0.3. Cyclic voltammetry reveals quasi-reversible redox behavior for both 1 and 3 with an unusually large ΔEp, assigned to the Mn(iii/ii) couple. Using the Bordwell method, the bond dissociation free energy (BDFE) of the O-H bond in {Mn(ii)-OH2} is estimated to be 67-70 kcal mol-1. Complex 3 abstracts H-atoms from 1,2-diphenylhydrazine, 2,4,6-TTBP, and TEMPOH, the latter of which supports a PCET mechanism. Under basic conditions in air, the synthesis of 1 results in K2[Mn(OAc)(pinF)2], 2, proposed to result from the oxidation of Et2O to EtOAc by a reactive Mn species, followed by ester hydrolysis. Complex 3 alone does not react with Et2O, but addition of O2 at low temperature effects the formation of a new chromophore proposed to be a Mn(iv) species. The related complexes K(18C6)[Mn(iii)(pinF)2], 4, and (Me4N)2[Mn(ii)(pinF)2], 5, have also been prepared and their properties discussed in relation to complexes 1-3.

Catecholase Activity of a Mn(III) Complex: An Approach through1H‐NMR spectroscopy

AbstractA mononuclear Mn(III) complex, [MnIIIL(Cl)], has been synthesized using a newly explored Schiff base ligand, H2L. Both of them have been characterized by single crystal X‐ray crystallography, UV‐Vis spectroscopy and IR spectroscopy. Interestingly the complex behaved as a model of catechol oxidase toward oxidation of 3,5‐Di‐tert‐butyl catechol to the corresponding quinone. The progress of the oxidation process has been monitored with the help of 1H‐NMR spectroscopy after stirring the reaction mixture in methanol for 2 hours, 24 hours, 36 hours and 48 hours at room temperature. NMR spectral data confirmed completion of the process after 48 hours. Kinetic investigations were carried out in two different solvents, methanol‐water mixture and acetonitrile to check the effect of solvent on the rate of reaction, if any. A greater turnover number was obtained in acetonitrile than methanol‐water medium.

Synthesis, characterization and superoxide dismutase activity of a biomimetic Mn(III) complex covalently anchored to mesoporous silica

A mononuclear Mn(III) complex of a clickable ligand, [Mn(hbpapn)(H2O)2]ClO4·4.5H2O, where H2hbpapn = 1,3-bis[(2-hydroxybenzyl)(propargyl)amino]propane, has been prepared and fully characterized. The complex catalyzes the dismutation of superoxide employing a Mn(III)/Mn(IV) redox cycle, with catalytic rate constant of 3.9 × 106 M−1 s−1 determined through the nitro blue tetrazolium photoreduction inhibition assay, in aqueous medium of pH 7.8. The alkyne function of the ligand was used for the covalent attachment of the catalyst to azide modified mesoporous silicas with different texture and morphology, through click chemistry. In these materials the catalyst is essentially linked to the inner pore walls, isolated and protected from the external medium. The hybrid materials can be recycled, and retain or improve the superoxide dismutase activity of the free catalyst with the pore size of the solid matrix playing a role on the activity of the catalyst.

Mononuclear manganese complexes as hydrogen evolving catalysts.

Molecular hydrogen (H2) is one of the pillars of future non-fossil energy supply. In the quest for alternative, non-precious metal catalysts for hydrogen generation to replace platinum, biological systems such as the enzyme hydrogenase serve as a blueprint. By taking inspiration from the bio-system, mostly nickel- or iron-based catalysts were explored so far. Manganese is a known oxygen-reducing catalyst but has received much less attention for its ability to reduce protons in acidic media. Here, the synthesis, characterization, and reaction mechanisms of a series of four mono-nuclear Mn(I) complexes in terms of their catalytic performance are reported. The effect of the variation of equatorial and axial ligands in their first and second coordination spheres was assessed pertaining to their control of the turnover frequencies and overpotentials. All four complexes show reactivity and reduce protons in acidic media to release molecular hydrogen H2. Quantum chemical studies were able to assign and interpret spectral characterizations from UV–Vis and electrochemistry and rationalize the reaction mechanism. Two feasible reaction mechanisms of electrochemical (E) and protonation (C) steps were compared. Quantum chemical studies can assign peaks in the cyclic voltammetry to structural changes of the complex during the reaction. The first one-electron reduction is essential to generate an open ligand-based site for protonation. The distorted octahedral Mn complexes possess an inverted second one-electron redox potential which is a pre-requisite for a swift and facile release of molecular hydrogen. This series on manganese catalysts extends the range of elements of the periodic table which are able to catalyze the hydrogen evolution reaction and will be explored further.

Manganese(II) coordination compounds of thiazole-hydrazone based NNN-donor ligands: Synthesis, characterization and catalytic activity

The reaction of Mn(OAc)2·4H2O with (E)-2-(2-(pyridin-2-ylmethylene)hydrazinyl)benzo[d]thiazole (HL1) and (E)-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)benzo[d]thiazole (HL2), in methanol resulted in the formation of [Mn(L1)2]∙2CH3OH (1) and [Mn(L2)2] (2) as neutral mononuclear Mn(II) coordination compounds. These compounds were characterized by spectroscopic methods and their molecular structures were determined by single crystal X-ray diffraction analysis. In these compounds, the ligands are coordinated to the Mn(II) core via the nitrogen atoms of thiazole ring, pyridine ring and imine moiety and act as tridentate mononegative NNN-donor ligand. The manganese(II) coordination compounds were also used as catalyst for olefin oxidation in the presence of tert-butylhydroperoxide (TBHP) or H2O2 as oxidant. Under similar experimental conditions with equal loading of Mn(II) coordination compounds, the presence of TBHP resulted in higher oxidation conversion than H2O2.

Investigation of electrocatalytic activity of a new mononuclear Mn(II) complex for water oxidation in alkaline media.

Water splitting is a promising way to alleviate the energy crisis. In nature, water oxidation is done by a tetranuclear manganese cluster in photosystem II. Therefore, the study of water oxidation by Mn complexes is attractive in water splitting systems. In this report, a new mononuclear Mn(II) complex, MnL2 (HL = (E)-3-hydroxy-N'-(pyridin-2-ylmethylene)-2-naphthohydrazide) was prepared and characterized by spectroscopic techniques and single-crystal X-ray diffraction. Crystallographic analysis indicated that the geometry around the Mn(II) ion is distorted octahedral. The MnN4O2 coordination moiety is achieved by bounding of oxygen and two nitrogen donor atoms of two hydrazone ligands. The synthesized complex was also investigated for electrochemical water oxidation using electrochemical techniques, scanning electron microscopy, energy dispersive spectrometry, and PXRD analysis. Linear sweep voltammetry experiment showed that the modified carbon paste electrode by the complex displays high activity for water oxidation reaction with an overpotential of 565mV at a current density of 10mAcm-2 and Tafel slope of 105mV dec-1 in an alkaline solution. It was found that the complex structure finally changes during the reaction and converts to Mn oxide nanoparticles which act as active catalytic species and oxidize the water.

Multinuclear Mn(II) united-DOTA complexes with enhanced inertness and high MRI contrast ability

Chelating lability significantly hinders the development of Mn(II)-based magnetic resonance image (MRI) contrast agents. Herein, using 1,4,7,10-tetraazacyclododecane- N , N ’, N ’’, N ’’’-tetraacetic acid (DOTA) as a chelating unit, we show that multinuclear Mn(II) united-DOTA chelates are of up to 69-fold higher inertness than Magnevist, a clinical Gd-based contrast agent. The unusual inertness could be ascribed to the multiplexed uniting of Mn(II) chelates, which is illustrated by a series of controlled studies on model compounds. Besides, molecular longitudinal relaxivities of Mn(II) united-DOTA chelates are 17–167 times higher than those of mononuclear Mn(II) complexes. Dynamic in vivo MRI experiments further reveal that Mn(II) united-DOTA complexes could provide more substantial and persistent contrast enhancement than both Mn-DOTA and Magnevist. Our efforts not only demonstrate that multinuclear Mn(II) united-DOTA complexes are a superior alternative to Gd-based contrast agents, but also highlight the significance of chelate unification as a simple yet powerful strategy for the construction of high-performance Mn(II)-based contrast agents. • Chelate unification plays an important role in inert enhancement of Mn(II) complexes • Chelate unification enhances both inertness and relaxivity of Mn(II) complexes • Multinuclear Mn(II) complexes feature promising in vivo MRI contrast ability Gd-based contrast agents are widely used in MRI but raise safety concerns. Sun et al. report a simple approach, chelate unification, to improve the kinetic inertness and relaxivity of Mn(II) complexes, offering a route to next-generation Gd-free MRI contrast agents.

Effect of halogen substituents on the intermolecular interactions and magnetic properties of Mn(III) complexes

Six mononuclear Mn(III) complexes with hexadentate Schiff-base ligand, the products of the reaction between a N,N′-bis(3-aminopropyl)ethylenediamine or triethylenetetramine and 5-X-salicylaldehyde have been synthesized: the I− salts of complexes 1–3 exhibit a gradual SCO behavior, [Mn(5-Cl-sal-N-1,5,8,12)]I (1) shows a nearly complete SCO with T1/2 = 125 K, whereas [Mn(5-Br-sal-N-1,5,8,12)]I (2) and [Mn(5-I-sal-N-1,5,8,12)]I (3) show a gradual and incomplete SCO above room temperature. [Mn(5-F-sal-N-1,4,7,10)]I (4) predominantly remains HS state at all temperatures. [Mn(5-I-sal-N-1,5,8,12)]NO3 (5) and [Mn(5-F-sal-N-1,5,8,12)]NO3 (6) show an almost full conversion to the HS state and a more gradual SCO having the T1/2 value of 282 K for 5 and 159 K for 6, respectively.

Antimicrobial activities of two 1‐D, 2‐D, and 3‐D mononuclear Mn (II) and dinuclear Bi (III) complexes: X‐ray structures, spectroscopic, electrostatic potential, Hirshfeld surface analysis, and time‐dependent/density functional theory studies

AbstractTwo mononuclear and dinuclear octahedral complexes, [Mn(L1)2Cl2] (1) and [Bi2(L2)2Cl8] (2) (L1 = 2‐(2‐pyridyl)‐4‐methyl‐1,2‐dihydroquinazoline‐N3‐oxide, L2 = 2‐(3‐pyridyl)‐4‐methyl‐1,2‐dihydroquinazoline‐N3‐oxide) were prepared by natural volatilization method. The ligands and both complexes were compared with spectroscopic methods, as well as characterized by elemental analysis. The photoluminescence behaviors of both complexes in different solvents were also investigated. The coordination possibility of ligands toward Mn (II)/Bi (III) was verified using X‐ray crystallography, and it revealed that the ratio of ligand to metal was 2:1 in 1, whereas 1:1 in 2. The adjacent molecules of six‐coordinated complex 1 constituted an infinite 1‐D chain, 2‐D network, and ladder‐like 3‐D supramolecular frameworks. Most strikingly, hexa‐coordinated complex 2 with dinuclear structure formed an infinite 1‐D chain, 2‐D layered and meter‐shaped 3‐D supramolecular skeleton. Density functional theory (DFT) calculation was used to optimize the geometry of complexes, compute the electrostatic potential diagrams, and evaluate the HOMO‐LUMO energy gap. The electronic transition simulated through time‐dependent (TD)‐DFT level of calculation rationalized the experimental data. The antibacterial properties of all compounds were evaluated against Gram‐positive and Gram‐negative bacterial strains. In addition, the Hirshfeld surface was utilized to quantify some hydrogen bonding interactions and their contributions.

Mechanism and origin of the stereoselectivity of manganese-catalyzed hydrosilylation of alkynes: a DFT study

The mechanism and origin of the stereodivergent mononuclear Mn(CO)5Br and binuclear Mn2(CO)10 catalyzed hydrosilylation of alkynes have been investigated and compared.

Electro-activating non-radical 1O2/H* via single atom manganese modified cathode: The indispensable role of metal active site Mn*

As an alternative to noble-metal Pt based catalysts, metal-based single atomic catalytic (SACs) exhibited excellent atom efficiency and catalytic activity via exposing abundant single atomic active centers. Here, we synthesized the monatomic Mn ligands anchored on porous N, P, S- co-doped carbon framework (Mn content over 4.5 wt%) (denoted as Mn-SAC@PZS). The single atomic Mn exhibited super mass activity (11.58 m2 g−1) and kinetic current (1.122×103 µA) with a much lower Tafel slope (4.25 mV dec−1) at 0.792 V (vs. SCE). XANES and EXAFS revealed that the mononuclear Mn were inclined to coordinate with N and S rather than P to form the R space of Mn, in which the first coordination shells backscattered with Mn-N and Mn-S. RRDE revealed that one-electron ORR pathway (72 ~ 100%) dominated at the potential of 0.5 ~ 0.7 V, oxygen molecule was absorbed/activated on site Mn* to form O* intermediate, then further activated to 1O2 via one-electron ORR pathway, while H* was electro activated by non-metallic active sites (i.e. pyri-N, sp-N, -PN and SO). In addition, the Mn-SAC@PZS was capable of highly selectively capturing and effectively degrading CIP in the presence of HA. Fast and complete removal of CIP was achieved within 30 min in the Mn-SAC@PZS-EFLP system, and the apparent rate constant (k) was up to 0.25 min−1. The energy consumption value was 0.453 kWh m−3, much lower than non-single atomic catalyst MnxOy@PZS (0.655 kWh m−3), which was comparable with the state-of-the-art advanced oxidation processes. These findings provided new insights into the maximum release of the atomic activity of the catalyst, and provides a possible way to selectively remove aromatics from multiple pollutants in complex water system.

Abrupt Spin-State Switching in Mn(III) Complexes with BPh4 Anion: Effect of Halide Substituents on Crystal Structure and Magnetic Properties.

Three tetraphenylborates of mononuclear Mn(III) cation complexes with hexadentate ligands, the products of the reaction between a N,N'-bis(3-aminopropyl)ethylenediamine and salicylaldehydes with the different haloid substitutions at the 5 or 3,5 positions, have been synthesized: [Mn(5-F-sal-N-1,5,8,12)]BPh4 (1), [Mn(3,5-diCl-sal-N-1,5,8,12)]BPh4 (2) and [Mn(3,5-Br,Cl-sal-N-1,5,8,12)]BPh4 (3). Their crystal structure, dielectric constant (ϵ) and magnetic properties have been studied. Ligand substituents have a dramatic effect on the structure and magnetic properties of the complexes. With decreasing temperature, the complex (1) shows a gradual spin crossover from the high-spin state (HS) to the HS:LS intermediate phase, followed by an abrupt transition to the low-spin state (LS) without changing the crystal symmetry. The complexes 2 and 3 are isostructural, but have fundamentally different properties. Complex 2 demonstrates two structural phase transitions related to sharp spin crossovers from the HS to the HS:LS intermediate phase at 137 K and from the intermediate phase to the LS at 87 K, while complex 3 exhibits only one spin transition from the HS to the HS:LS intermediate phase at 83 K.