Mn Salen Complexes Research Articles

Heteronuclear Fe(III)/Mn(III) salen complex as electron transfer mediator for laccase-based biocathodes: Structural investigations, molecular docking, and electrochemical studies

A novel hetero-trinuclear Fe(III)/Mn(III) complex derived from a salen ligand has been investigated using elemental analysis, infrared spectroscopy, and single-crystal X-ray crystallography. The studied complex crystallized as orthorhombic with the Mn(III) ion coordinated in the equatorial plane by the phenolate O and imine N atoms of the ligand. Two axial positions are taken up by an O atom from water and a N atom from the cyanide group. The [Fe(CN)6] core in the crystal structure links the two [Mn(salen)(H2O)] moieties together. In addition, the isolated complexes have been utilized as mediators for the electron transfer between the laccase and the electrode. Moreover, using structural data for the laccase, computational docking simulations were also performed towards the hydrophobic pocket on the surface of the laccase to determine how the complex behaved in the vicinity of a so-called hydrophobic pocket on the surface outside of the Type-1 site. Additionally, the parameters of mediator concentration, temperature, and electrode conditions (CNT, MXene) were used to investigate the electron transfer mechanism.

Unsymmetric bi-functional Mn-salen complex bearing TEMPO and Mn-complex for the synthesis of magnetic Mn/TEMPO-doped Fe3O4 NPs: a simple catalyst (magnetic oxidant) for selective oxidation of alcohols

Unsymmetric bi-functional Mn-salen complex bearing TEMPO and Mn-complex for the synthesis of magnetic Mn/TEMPO-doped Fe3O4 NPs: a simple catalyst (magnetic oxidant) for selective oxidation of alcohols

Synthesis of Highly Porous Mn2O3-Doped Fe3O4 NPs with a Dual Catalytic Function Using Asymmetric Water Soluble Mn-Salen Complex as a Reducing Agent and Template: Catalytic Activity over One-Pot Strecker Synthesis from Alcohols in Recyclable TAIm[CN] Ionic Liquid

Synthesis of Highly Porous Mn2O3-Doped Fe3O4 NPs with a Dual Catalytic Function Using Asymmetric Water Soluble Mn-Salen Complex as a Reducing Agent and Template: Catalytic Activity over One-Pot Strecker Synthesis from Alcohols in Recyclable TAIm[CN] Ionic Liquid

Asymmetric Epoxidation of Unfunctionalized Olefins Catalyzed by Chiral (Pyrrolidine Salen) Mn (III) Complexes with Proline Sidearms

Four (R, R)-3, 4-diaminopyrrolidine-based chiral Salen ligands with L-Boc-N-proline, D-Boc-N-proline, L-proline, D-proline as respective sidearms, as well as their manganese complexes were synthesized and characterized. These Salen-Mn(III) complexes were applied to the asymmetric epoxidations of unfunctionalized olefins with NaClO, and m-CPBA as respective oxidants. The catalysis of the Salen-Mn (III) complexes varied with the change of sidearms. The one with D-Boc-N-proline as a sidearm showed the best asymmetric catalysis among the four chiral manganese complexes, and its catalysis was also better than that of the one with a benzyl sidearm, and comparable with that of Jacobsen's catalyst. Moderate to excellent enantioselectivities and yields were achieved in the asymmetric of various olefins over this complex. The big enhancement of the D-Boc-N-proline sidearm on the enantioselectivity of the asymmetric epoxidation might be ascribed to its large steric hindrance and appropriate configuration, allowing the Boc moiety to be away from the side-on approach pathway of olefins to the active center but near the opposite side one in some degree, thus facilitating the approach of olefins to the active center from one direction.

Retraction: Synthesis of a novel type of chiral salen Mn(iii) complex immobilized on crystalline zinc poly(styrene-phenylvinylphosphonate)-phosphate (ZnPS-PVPP) as effective catalysts for asymmetric epoxidation of unfunctionalized olefins

Retraction for ‘Synthesis of a novel type of chiral salen Mn(iii) complex immobilized on crystalline zinc poly(styrene-phenylvinylphosphonate)-phosphate (ZnPS-PVPP) as effective catalysts for asymmetric epoxidation of unfunctionalized olefins’ by Jing Huang et al., Catal. Sci. Technol., 2011, 1, 1472–1482, DOI: 10.1039/C1CY00285F

The electrochemical reduction of a flexible Mn(II) salen-based metal-organic framework.

A new metal-organic framework (MOF) containing a Mn(II) salen complex (BET surface area = 967 ± 6 m2 g-1) undergoes a reversible crystalline-to-amorphous transformation. Experimental studies and computational calculations show that the MOF is stable to a one-electron reduction at more anodic potentials than the corresponding discrete complex.

Chiral Mn(III) Salen Complex Immobilized on CuFe2O4@SiO2-NH2 NPs: A Cheap and Efficient Catalyst for N-arylation of Aryl Halides and Phenylboronic Acid Under Mild Conditions

A convenient and efficient chiral CuFe2O4@SiO2-Mn(III) Ch.salen nanocatalyst has been developed for the C-N cross-coupling reactions of aryl halides/ phenylboronic acid with N-heterocyclic compounds in water and/or DMSO under mild conditions. The catalyst could be applied for the N-arylation of a variety of nitrogen-containing heterocycles with aryl chlorides, bromides, iodides and phenylboronic acid under mild conditions. Moderate to good yields were achieved for all substrates. The structure of catalyst was characterized using various techniques including FT-IR, FE-SEM, EDX, XRD, TEM and TGA. The catalyst can be simply recovered and reused for several times without significant loss of activity.

Characterization and Catalytic Activity of Mn(salen) Supported on a Silica/Clay-Mineral Composite: Influence of the Complex/Support Interaction on the Catalytic Efficiency

We investigated different strategies to prepare Mn(salen) complexes supported on a silica/clay-mineral composite. The silica/clay-mineral surfaces were modified by grafting aminosilane groups, then Mn(salen) complexes were either grafted through a cross-linker, or deposited on the surface through interactions between amino group and manganese center. Two additional strategies, based on hydrogen bonds and electrostatic interactions, were also considered for comparison. The resulting materials were characterized using IR in diffuse reflectance mode, thermogravimetric analysis and elemental analysis in order to determine the manganese content and to establish the nature of the interaction between Mn(salen) complexes and silica/clay-mineral material surface for the different preparation protocols. These catalysts, were used for cyclohexene oxidation by tert-Butyl hydroperoxide with the objective of correlating the nature of the interaction between the metallic complex and the support to the catalytic activity. They were also compared to similar systems prepared using fumed silica as support, evidencing the input of this silica/clay-mineral composite in the catalytic performances. The obtained materials exhibited differences in both reactivity and selectivity that can be related to the nature of the interaction between the metallic center and the oxide support. The highest conversions were observed when the Mn complexes were immobilized with rigidness on the support. Interestingly, the resulting materials exhibited a remarkable stability, as evidenced by the absence of leaching of Mn(salen) in the reaction batch, and hence an excellent reusability.

Substituted effect on some water-soluble Mn(II) salen complexes: DNA binding, cytotoxicity, molecular docking, DFT studies and theoretical IR & UV studies.

Based on the importance of central metal complexes to interact with DNA, in this research focused on synthesis of some new water soluble Mn(II) complexes 1-4 which modified substituted in ligand at the same position with N, Me, H, and Cl. These complexes were isolated and characterized by elemental analyses, FT-IR, electrospray ionization mass spectrometry (ESI-MS) and UV-vis spectroscopy. DNA binding studies had been studied by using circular dichroism (CD) spectroscopy, UV-vis absorption spectroscopy, cyclic voltammetry (CV), viscosity measurements, emission spectroscopy and gel electrophoresis which proposed the metal buildings go about as effective DNA binders were studied in the presence of Fish-DNA (FS-DNA) which showed the highest binding affinity to DNA with hydrophobic and electron donating substituent. Cell toxicity assays against two human leukemia (Jurkat) and breast cancer (MCF-7) cell lines showed that the complex 3 exhibited a remarkable effects equal to a famous anticancer drug, cisplatin that high cytotoxic activity strongly depend on the hydrophobic substituted ligand. In the theoretical part, density functional theory (DFT) was performed to optimize the geometry of complexes through IR and UV spectra of the complexes that ligand substitution did not affect the geometry and theoretical IR and UV spectra showed good resemblance to the experimental data. The docking studies calculated the lowest-energy between complexes and DNA with the minor grooves mode.

Potential Therapeutic Applications of MnSODs and SOD-Mimetics.

Natural as well as synthetic antioxidants are constantly being investigated for their efficiency in combatting the effects of oxidative stress, which appears to be the responsible cause of several diseases, including cancer, central nervous system disorders, ischaemia-reperfusion disorders, cardiovascular conditions, and diabetes. Superoxide dismutases (SODs) constitute the ubiquitous antioxidant defences against oxidative stress that underlies numerous pathological conditions. Therefore, the development of therapeutics aimed at either delivering MnSOD more effectively to target tissues in the body in the form of MnSOD gene therapy, or the synthesis of molecules that mimic the activity of superoxide dismutase is constantly being explored. Classes that have been developed as SOD mimetics include the Mn-metalloporphyrins, Mn-cyclic polyamines, Mn-salen complexes, MnPLED derivatives as well as the nitroxides. Thus far, SOD mimetics have shown remarkable efficacy in several animal models suffering from oxidative stress injuries. A promising approach for the future of SOD and SOD mimic therapeutics appears to involve combination treatment of the antioxidants with radiotherapy or chemotherapy.

Advances in asymmetric oxidative kinetic resolution of racemic secondary alcohols catalyzed by chiral Mn(III) salen complexes.

Enantiomerically pure secondary alcohols are essential compounds in organic synthesis and are used as chiral auxiliaries and synthetic intermediates in the pharmaceutical, agrochemical, and fine chemical industries. One of the attractive and practical approaches to achieving optically pure secondary alcohols is oxidative kinetic resolution of racemic secondary alcohols using chiral Mn(III) salen complexes. In the last decade, several chiral Mn(III) salen complexes have been reported with excellent enantioselectivity and activity in the homogeneous and heterogeneous catalysis of the oxidative kinetic resolution of racemic secondary alcohols. This review article is an overview of the literature on the recent development of chiral Mn(III) salen complexes for oxidative kinetic resolution of racemic secondary alcohols. The catalytic activity of monomeric, dimeric, macrocyclic, polymeric, and silica/resin supported chiral Mn(III) salen complexes is discussed in detail.

Synthesis of Chiral Salen Mn (III) Complex Immobilized on Phenoxy-modified AlPS-PVPA as Catalysts for Epoxidation of Olefins

以有机共聚物-无机杂化材料聚（苯乙烯-苯乙烯基膦酸）-磷酸铝（AlPS-PVPA）为载体，酚氧基为连接基团，轴向配位手性salen Mn（Ⅲ）制备了新型固载手性salen Mn（Ⅲ）催化剂，并运用FT-IR，UV-vis，XPS，SEM，TG，元素分析等手段对其进行了表征.以 m -CPBA为氧化剂，茚和 α -甲基苯乙烯为底物，考察了催化剂对非功能化烯烃不对称环氧化反应的催化性能.结果表明，在相同的条件下，固载催化剂 3a ~ 3d 在不加助催化剂NMO时显示出了优良的催化活性，其转化率和 ee 值均比添加了轴向配体NMO时有很大的提高（ ee %，99.2 vs.45.9；conv%，98.6 vs.64.6），这种现象与大多数文献报道相反.此外，催化剂容易分离，且回收使用9次仍能保持较好的催化活性.

Layered crystalline chiral salen Mn(III) complexes immobilized on organic polymer–inorganic hybrid zinc phosphonate-phosphate as efficient and reusable catalysts for the unfunctionalized olefin epoxidation

Chiral Mn(III) salen complexes grafted on ZnPS-PVPA (zinc poly(styrene-phenylvinyl-phosphonate)-phosphate) upon alkyldiamines through a facile method are evaluated by the asymmetric epoxidation of unfunctionalized olefins. Superior catalytic performances are obtained (conv%, up to >99; ee%, up to >99) whenever with m-CPBA or NaClO or NaIO4 as the oxidant. The additives such as NMO, PPNO as well as imidazole play different roles in the corresponding oxidation system. In addition, the supported catalysts could be reused nine times with the retention of their efficiency. These results highlight the potentiality of ZnPS-PVPA as the support for immobilizing chiral salen Mn(III) to be employed in oxidation reactions.

Aminopropyl group-modified SBA-15 covalent attachment Mn(salen) complexes as catalysts for styrene epoxidation

GRAPHICAL ABSTRACT

Microfluidic synthesis of chiral salen Mn(ii) and Co(ii) complexes containing lysozyme

Efficient microfluidic synthesis of chiral salen Mn(ii) and Co(ii) complexes containing lysozyme was achieved.

Catalytic activity of reusable Mn(II) salen complex immobilized on nano silicagel in the oxidation of sulfides

Mn salen complexes immobilized on nanosilicagel was prepared by incorporating Mn salen complexes into a nanosilica matrix characterized by TGA, XRD, and atomic absorption spectroscopy. This catalyst can be successfully applied as a reusable catalyst for the oxidation of sulfides. Oxidation of a series of sulfides in water as a green solvent over immobilized Mn salen complex with TBAO as oxidant resulted in the corresponding sulfoxides selectively in moderate to high yields. The catalyst has been reused several times, without observable loss of activity and selectivity.

Structure and asymmetric epoxidation reactivity of chiral Mn(iii) salen catalysts modified by different axial anions

The axial anions influence the electronic structure, steric configuration, and enantioselectivity of the chiral Mn(iii) salen complexes.

Ionic liquid-functionalized graphene oxide as an efficient support for the chiral salen Mn(iii) complex in asymmetric epoxidation of unfunctionalized olefins

Chiral salen Mn(iii) complex covalently grafted on IL-functionalized GO sheet, was a highly efficient, universal and reusable catalyst for asymmetric epoxidation of unfunctionalized olefins using aqueous NaOCl as an oxidant.

Reusable chiral salen Mn(III) complexes with phase transfer capability efficiently catalyze the asymmetric epoxidation of unfunctionalized olefins with NaClO

A series of chiral salen Mn(III) polymers with build-in phase transfer capability was prepared by bridging the chiral salen Mn(III) units with polyethylene glycol (PEG)-based di-imidazolium ionic liquid (IL) side by side. Technologies of characterization suggested the alternation of intact chiral salen Mn(III) unit with PEG-based dicationic imidazolium IL moiety in the rigid one-dimension polymers. Amphipathic nature of PEG-based di-imidazolium IL moiety allowed the obtained catalysts to undergo inherent phase transfer catalysis in asymmetric epoxidation of unfunctionalized olefins with NaClO, which in turn increased the reaction rate of epoxidation in water–dichloromethane biphasic system. Decreasing total length of polyether chain leads to an increase in built-in phase transfer capability of corresponding complex, which further enhances the catalytic performance. 91–97% of conversion was obtained in the enantioselective epoxidation of styrene, α-methylstyrene, indene, 1,2-dihydronaphthalene, 6-cyano-2,2-dimethylchromene, and 6-nitro-2,2-dimethylchromene catalyzed by the complex where number of ethylene oxide unit is 3 within 60min, which is significant higher than that observed for the neat complex (56–74%) and the ICP (62–85%). High enantiomeric excess (ee) for the epoxides (in the range of 67–93%) was also achieved, except for styrene (ee, 34%) and α-methylstyrene (ee, 41%). Furthermore, the efficient phase transfer catalysts could be easily recovered by solvent precipitation and be recycled for seven times without significant loss of the activity and enantioselectivity.

Mesoporous material AlPS-BrPPAS derivatives supported chiral Mn(III) salen complex and highly efficient epoxidation of olefins as a recoverable catalyst

A novel layered crystalline of organic–inorganic hybrid material aluminium 3-bromopropylphosphonate-phosphate (AlPS-BrPPAS) was synthesized and used as catalyst supports for immobilization of chiral salen Mn(III) with different types of diamine linkers. The heterogeneous salen Mn(III) catalysts were characterized by FT-IR, XRD, TG, SEM, and N2 sorption, and the results indicated the successful immobilization of the chiral Mn(III) salen complex. It was found that the structure of the catalysts was closely correlated with the linkers. The confinement effect of linkers on the catalytic performance of the heterogeneous catalysts was studied for the asymmetric epoxidation of unfunctionalized olefins with sodium hypochlorite as an oxidant. Moreover, the heterogeneous chiral salen Mn(III) catalysts can be recovered and reused up to nine times with retention of conversion and enantioselectivity. Interestingly, two heterogeneous chiral salen Mn(III) catalysts with different linkers also significantly alter the configuration of epoxide products for 6-cyano-2,2-dimethylchromene and 6-nitro-2,2-dimethyl-chromene.