Manganese Complexes Research Articles

Synthesis, characterization, biological activity and molecular docking study of transition metal complexes from heterocyclic ligand system

The bivalent metal chelates of manganese, cobalt, nickel, copper, and zinc have been synthesized from 3-acetylcoumarin derivative. The compounds were characterized using elemental analysis and spectral techniques such as molar conductance, IR, UV, magnetic moment, 1H NMR, 13C NMR, mass, EPR, and fluorescence studies. The ligand (IMAC) coordinates to the metal ion in tridentate binding mode through the amide carbonyl, azomethine nitrogen and lactone carbonyl oxygen of the coumarin moiety. All the complexes have octahedral geometry. XRD data revealed that the ligand is crystalline in nature and all the complexes are amorphous in nature. The DNA cleavage activities of the compounds have been studied using pUC18 plasmid DNA and the results showed moderate activity. The antifungal activities were examined by disc diffusion method. Cobalt(II), nickel(II), copper(II) and zinc(II) complexes displayed good activity when compared to the ligand and manganese(II) complex. The antibacterial activities have been evaluated against Staphylococcus aureus and Escherichia coli. The nickel(II) complex showed more pronounced activity than other compounds. The antioxidant activity of manganese, cobalt and zinc chelates exhibited excellent percentage of inhibition than the ligand. The in vitro anticancer activity is studied against human cancer cell lines such as Breast cancer cell (MCF-7) and Leukemia cancer cell (K-562) with standard drug adriamycin. The results showed moderate activity compared with standard drug. Furthermore, molecular docking of ligand and nickel(II) complex is investigated with CDK2 protein and concluded that nickel(II) complex has better binding affinity than ligand.

Electrochemical Epoxidation Catalyzed by Manganese Salen Complex and Carbonate with Boron-Doped Diamond Electrode.

Epoxides are essential precursors for epoxy resins and other chemical products. In this study, we investigated whether electrochemically oxidizing carbonate ions could produce percarbonate to promote an epoxidation reaction in the presence of appropriate metal catalysts, although Tanaka and co-workers had already completed a separate study in which the electrochemical oxidation of chloride ions was used to produce hypochlorite ions for electrochemical epoxidation. We found that epoxides could be obtained from styrene derivatives in the presence of metal complexes, including manganese(III) and oxidovanadium(IV) porphyrin complexes and manganese salen complexes, using a boron-doped diamond as the anode. After considering various complexes as potential catalysts, we found that manganese salen complexes showed better performance in terms of epoxide yield. Furthermore, the substituent effect of the manganese salen complex was also investigated, and it was found that the highest epoxide yields were obtained when Jacobsen's catalyst was used. Although there is still room for improving the yields, this study has shown that the in situ electrochemical generation of percarbonate ions is a promising method for the electrochemical epoxidation of alkenes.

Two Schiff-base complexes of cadmium and manganese on modified MCM-41 as practical, recyclable and selective nanocatalysts for the synthesis of sulfoxides

Two Schiff-base complexes of cadmium and manganese on modified MCM-41 as practical, recyclable and selective nanocatalysts for the synthesis of sulfoxides

Syntheses, structural characterizations, and catalytic activities of manganese(II)-aroylhydrazone complexes

An aroylhydrazone, di-2-pyridyl ketone-4-methoxybenzhydrazone monohydrate (DKMBH·H2O), and its three Mn(II) complexes, [Mn(DKMB)2]·H2O (1), [Mn(DKMB)Cl] (2), and [Mn(DKMB)NO3] (3), were synthesized. The physicochemical properties of the aroylhydrazone and metal complexes were revealed using various methods, e.g., Fourier transform infrared (IR) spectroscopy, ultraviolet-visible spectroscopy, mass spectrometry, and 1H nuclear magnetic resonance (NMR) spectroscopy, in addition to analyses such as CHN elemental and thermal analyses and molar conductivity studies. The molecular structures of the aroylhydrazone and manganese complex, 1 were elucidated using single-crystal X-ray diffraction (XRD) analyses.IR spectroscopy, 1H NMR spectroscopy, and single-crystal XRD showed that the aroylhydrazone occurred in the amido form in the solid state. According to the results of XRD, the aroylhydrazone coordinated to the Mn(II) center via the pyridine and azomethine N atoms and iminolate O atom, with a distorted octahedral geometry, in bis-ligated complex, 1.The results of IR spectroscopy further supported the tridentate character of the aroylhydrazone. Furthermore, the Mn complexes displayed potential as catalysts in cyclooctene epoxidation. Among the three Mn complexes, the use of [Mn(DKMB)2]·H2O (1) resulted in a 92% conversion, with an epoxide selectivity of 95%.

Development and Evaluation of the Magnetic Properties of a New Manganese (II) Complex: A Potential MRI Contrast Agent.

Magnetic resonance imaging (MRI) is a non-invasive powerful modern clinical technique that is extensively used for the high-resolution imaging of soft tissues. To obtain high-definition pictures of tissues or of the whole organism this technique is enhanced by the use of contrast agents. Gadolinium-based contrast agents have an excellent safety profile. However, over the last two decades, some specific concerns have surfaced. Mn(II) has different favorable physicochemical characteristics and a good toxicity profile, which makes it a good alternative to the Gd(III)-based MRI contrast agents currently used in clinics. Mn(II)-disubstituted symmetrical complexes containing dithiocarbamates ligands were prepared under a nitrogen atmosphere. The magnetic measurements on Mn complexes were carried out with MRI phantom measurements at 1.5 T with a clinical magnetic resonance. Relaxivity values, contrast, and stability were evaluated by appropriate sequences. Studies conducted to evaluate the properties of paramagnetic imaging in water using a clinical magnetic resonance showed that the contrast, produced by the complex [Mn(II)(L')2] × 2H2O (L' = 1.4-dioxa-8-azaspiro[4.5]decane-8-carbodithioate), is comparable to that produced by gadolinium complexes currently used in medicine as a paramagnetic contrast agent.

Organic–Inorganic Manganese (II) Halide Hybrid Combining the Two Isomers Cis/Trans of [MnCl4(H2O)2]: Crystal Structure, Physical Properties, Pharmacokinetics and Biological Evaluation

A manganese (II) complex templated by hexahydro-1,4-diazepinediium as a counter ion was grown by slow evaporation from an aqueous solution at room temperature. The X-ray diffraction analysis revealed that the compound (C5H14N2)[MnCl4(H2O)2] crystallizes in the centrosymmetric space group P2/c of the monoclinic system. The crystal structure of the Mn(II) complex is characterized by an alternation of 0-dimensional organic and inorganic stacks linked together by N/O-H…Cl and N-H…O hydrogen bonds, which lead to a three-dimensional supramolecular architecture. In this structure, the inorganic layer is built up by independent anionic moieties combining the two isomers cis/trans of [MnCl4(H2O)2]2−. The thermal decomposition was studied by TGA-DTA techniques. The optical band gap and Urbach energy were obtained by Tauc’s equation. The direct and indirect band gap values are found to be 4.58 and 4.44 eV, respectively. Weak antiferromagnetic interactions are present in the molecule under study, according to magnetic measurements. An agar well diffusion technique was used to assess the synthetic compound’s biological activity, and the results showed that it has potent antibacterial (Gram-positive and Gram-negative) properties. Interestingly, the synthesized compound also displayed antilipase activity. These biological activities have been confirmed by the bioavailability and pharmacokinetic analyses.

Sustainable Synthesis of α-Hydroxycarboxylic Acids by Manganese Catalyzed Acceptorless Dehydrogenative Coupling of Ethylene Glycol and Primary Alcohols.

Herein, we report a straightforward synthesis of valuable α-hydroxycarboxylic acid molecules via an acceptorless dehydrogenative coupling of ethylene glycol and primary alcohols. A bench-stable manganese complex catalyzed the reaction, which is scalable, with the product being isolated with high yields and selectivities under mild conditions. The protocol is environmentally benign, producing water and hydrogen gas as the only byproducts. Methanol can also be used as a C1 source for producing the platform molecule lactic acid, with a high turnover of >104 . The methodology was also used to functionalize alcohols derived from natural products and fatty acids. Furthermore, it was applied for synthesizing α-amino acid, α-thiocarboxylic acid, and several drugs and bioactive molecules, including endogenous metabolites, Danshensu, Enalapril, Lisinopril, and Rosmarinic acid. Preliminary mechanistic studies were performed to shed light on the mechanism involved in the reaction.

Sustainable Synthesis of α‐Hydroxycarboxylic Acids by Manganese Catalyzed Acceptorless Dehydrogenative Coupling of Ethylene Glycol and Primary Alcohols**

AbstractHerein, we report a straightforward synthesis of valuable α‐hydroxycarboxylic acid molecules via an acceptorless dehydrogenative coupling of ethylene glycol and primary alcohols. A bench‐stable manganese complex catalyzed the reaction, which is scalable, with the product being isolated with high yields and selectivities under mild conditions. The protocol is environmentally benign, producing water and hydrogen gas as the only byproducts. Methanol can also be used as a C1 source for producing the platform molecule lactic acid, with a high turnover of >104. The methodology was also used to functionalize alcohols derived from natural products and fatty acids. Furthermore, it was applied for synthesizing α‐amino acid, α‐thiocarboxylic acid, and several drugs and bioactive molecules, including endogenous metabolites, Danshensu, Enalapril, Lisinopril, and Rosmarinic acid. Preliminary mechanistic studies were performed to shed light on the mechanism involved in the reaction.

Electrochemical Characterization and CO2 Reduction Reaction of a Family of Pyridazine-Bridged Dinuclear Mn(I) Carbonyl Complexes.

Three recently synthesized neutral dinuclear carbonyl manganese complexes with the pyridazine bridging ligand, of general formula [Mn2(μ-ER)2(CO)6(μ-pydz)] (pydz = pyridazine; E = O or S; R = methyl or phenyl), have been investigated by cyclic voltammetry in dimethylformamide and acetonitrile both under an inert argon atmosphere and in the presence of carbon dioxide. This family of Mn(I) compounds behaves interestingly at negative potentials in the presence of CO2. Based on this behavior, which is herein discussed, a rather efficient catalytic mechanism for the CO2 reduction reaction toward the generation of CO has been hypothesized.

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.

Advances in the homogeneous catalyzed alcohols homologation: The mild side of the Guerbet reaction. A mini-review

The Guerbet reaction would be an optimal solution for bio-ethanol refinery by homologation and it substantially requires the development of active and highly selective catalysts. Although heterogeneous catalysis remains more desirable, homogeneous Guerbet catalytic systems are nowadays acknowledged as challenging proposals for high selectivity and conversion under mild reaction conditions. Several molecular bi-functional catalysts, based on ruthenium, iridium and manganese complexes bearing different ligands such as phosphine, bidentate bisphosphine (P-P) and phosphamine (P-N), pincer (N-N-N), (P-N-P) and cyclopentadienone, are active in the co-presence of a base, which is essential in all the cases for the condensation reaction. This mini-review is aimed to describe the state of the art, with incremental steps forward to understand the role of the catalytic systems and the reaction conditions on conversion and selectivity. While showing different efficiency, mutable behavior by minimal change in the ligand scaffold, variation in water tolerance and only one example of recyclability, metal catalysts are found to be similar in terms of proposed mechanisms. The influence of additives and capability to maintain activity in fermentation broth and bio-ethanol from wine value chain to second generation bio-fuel are also discussed. Although not yet completely rationalized, experimental and theoretical mechanistic investigations pave the way for the design of more stable and efficient catalysts toward improved applicability.

Synthesis, spectroscopic investigation and bioactivities of metal complexes from curcuma longa derivative

Curcumin and isatin derivatives demonstrated vital role in biological activities. In view of their biological significance, potentially tridentate ligand was synthesized from curcumin derivative and its bivalent manganese, cobalt, nickel, copper and zinc complexes are synthesized and investigated spectrochemical studies based on elemental analysis, IR, Ultraviolet–visible, NMR (1H and 13C) and EPR studies. EPR spectrum of copper(II) system noticed considerable covalent character. Spectroscopic analysis revealed that chelation of ligand and metal ion with deprotonation of enolate oxygen, azomethine nitrogen and carbonyl oxygen. The ligand and crystalline complexes were subjected to powder X-ray diffraction analysis. The emission peaks are noted in the range between ∼500–700 nm wavelengths observed by fluorescence spectroscopy. Samples were tested to antifungal, antibacterial (MIC) and antioxidant activities. Biological results were showed high to moderate activity against various microorganisms. The DNA cleavage ability indicated effective cleavage activity. Compounds have been screened towards human breast cancer (MCF-7) and leukemia (K-562) cell lines. They evidenced potent effect against growth of cancer cell lines compared to the effective anticancer agent Adriamycin. Hence the compounds can be considered to design a promising chemotherapeutic agent and excellent tool for cellular imaging.

Efficiency of using different levels of mixed ligand complexes of Zinc, Manganese, and Cobalt in cow feeding

To increase productivity and reduce the negative impact on the environment, it is necessary to investigate the most optimal ratios of organic trace elements in the diets of cows involved in the production cycle, considering their physiological state and lactation stage. The purpose of the study was to determine the economic profitability of using mixed complexes of zinc, manganese, and cobalt in the diets of dairy cows. The experiment was carried out under production conditions on Holstein cows. 100 cows were divided into two groups. Cows of the control and experimental groups consumed feed mixtures made according to the same recipes, supplemented with mixed ligand complexes of zinc, manganese, and cobalt. It was found that with the optimal content of mixed ligand complexes of zinc, manganese, and cobalt in cows of the experimental group, body weight loss during the first hundred days of lactation was 16.4 kg or 2.88% less than in the control. Analysis of performance indicators of cows during the dry period and the first hundred days of lactation showed that in animals of the experimental group, whose diet contained mixed ligand complexes of trace elements at the rate of 54.7 mg of zinc and manganese and 0.7 mg of cobalt per 1 kg of dry matter, milk yields of natural fat content increased by 4.1 kg or 9.2%, the fat content in milk – by 0.02% compared to cows of the control group, whose diets provided the content of zinc and manganese at the level of 60.8 mg, cobalt – 0.78 mg/kg of dry matter due to mixed ligand complexes. There was also a decrease in the duration of the service period by 9 days and the insemination index by 0.17 semen doses. The cost of production remained unchanged, and the additional profit with a reduced concentration of these elements in the diet of cows of the experimental group amounted to EUR 27.24 or 9.7%. Thus, optimisation of mineral nutrition of cows by introducing mixed ligand complexes of zinc, manganese, and cobalt to achieve the concentration of trace elements of zinc and manganese – 54.7 mg each, and cobalt – 0.7 mg per 1 kg of dry matter of the feed mixture will improve milk production and reproductive capacity of cows and allow obtaining additional profit

The Golgi-localized transporter OsPML3 is involved in manganese homeostasis and complex N-glycan synthesis in rice.

Manganese (Mn) is involved in many biochemical pathways as an enzyme cofactor, and is essential for maintaining metabolic processes in various plant cell compartments. Here, we determined the function of a rice (Oryza sativa) Mn transporter, PHOTOSYNTHESIS-AFFECTED MUTANT 71-LIKE 3 (OsPML3), belonging to the UNCHARACTERIZED PROTEIN FAMILY 0016 (UPF0016), in regulating Mn homeostasis and late-stage Golgi N-glycosylation. OsPML3 was highly expressed in rapidly developing tissues such as young leaves, root caps, lateral root primordia, and young anthers. Heterologous expression of OsPML3 restored the growth of Mn uptake-defective yeast strain Δsmf1 under Mn-limited conditions. Sub-cellular localization analysis revealed that OsPML3 localizes in the Golgi apparatus. At the vegetative stage, we observed necrotic root tips and lateral root primordia, and chlorotic young leaves in OsPML3 knockout lines under Mn-deficient conditions. Knocking out OsPML3 reduced the Mn content in the young leaves but did not affect the older leaves. Additionally, knocking out OsPML3 reduced the deposition of cell wall polysaccharides and the content of Lea (Lewis A structure)-containing N-glycan in roots and young leaves. OsPML3 knockout lines grown in the paddy field had reduced pollen fertility. Moreover, we found that the Lewis A structure was reduced in young anthers of OsPML3 knockout lines. Collectively, our results indicate that OsPML3 maintains Mn homeostasis in the Golgi apparatus of the rapidly developing rice tissues, and regulates the deposition of cell wall polysaccharides and late-stage Golgi N-glycosylation, especially biosynthesis of the Lewis A structure.

Macrocyclic pseudo crown-ether- manganese (II) complex coated on nanomagnetic LDH- catalyzed Biginelli annulation reactions

A single-site macrocyclic pseudo crown ether-manganese complex was generated from the complexation of a new tetradentate ligand brought from a synthetic procedure with manganese (II) halide precursor in an electron-transfer process. The prepared [γ-Fe2O3@LDH/PCE-Mn(II)] acts as an efficient heterogeneous Mn-based catalyst – exhibiting efficient catalytic activity in the synthesis of the functionalized chromeno-pyrimidines via a Biginelli-like annulation process. Moreover, Biginelli reaction of a variety of aryl aldehydes and carbamide/thiocarbamide with a β-ketoester moiety was achieved in ethanol at 60 °C with 65–92% yield in 10–40 min. This catalytic process can be initiated using the Mn(II)-catalyzed in situ generation of an imine intermediate. Subsequently, the addition of a β-ketoester moiety – followed by the ring-closure reaction and removal of a water molecule – forms a library of new chromeno-pyrimidine-2,5-diones/thione products with a broad substrate scope.

A macrocyclic quinol-containing ligand enables high catalase activity even with a redox-inactive metal at the expense of the ability to mimic superoxide dismutase.

Previously, we found that linear quinol-containing ligands could allow manganese complexes to act as functional mimics of superoxide dismutase (SOD). The redox activity of the quinol enables even Zn(ii) complexes with these ligands to catalyze superoxide degradation. As we were investigating the abilities of manganese and iron complexes with 1,8-bis(2,5-dihydroxybenzyl)-1,4,8,11-tetraazacyclotetradecane (H4qp4) to act as redox-responsive contrast agents for magnetic resonance imaging (MRI), we found evidence that they could also catalyze the dismutation of H2O2. Here, we investigate the antioxidant behavior of Mn(ii), Fe(ii), and Zn(ii) complexes with H4qp4. Although the H4qp4 complexes are relatively poor mimetics of SOD, with only the manganese complex displaying above-baseline catalysis, all three display extremely potent catalase activity. The ability of the Zn(ii) complex to catalyze the degradation of H2O2 demonstrates that the use of a redox-active ligand can enable redox-inactive metals to catalyze the decomposition of reactive oxygen species (ROS) besides superoxide. The results also demonstrate that the ligand framework can tune antioxidant activity towards specific ROS.

Chemoselective C(sp)–H borylation of terminal alkynes catalyzed by a bis(N-heterocyclicsilylene) manganese complex

The manganese(ii) complex [Mn(SiNSi)Cl2] (SiNSi = 2,6-[EtNSi(NtBu)2CPh]2C5H3N) is an efficient catalyst for the chemoselective C(sp)–H borylation of terminal alkynes.

Spin-state switching: chemical modulation and the impact of intermolecular interactions in manganese(III) complexes.

A series of mononuclear manganese(III) complexes [Mn(X-sal2-323)](ReO4) (X = 5 Cl, 1; X = 5 Br, 2; X = 3,5 Cl, 3; X = 3,5 Br, 4; and X = 5 NO2, 5), containing hexadentate ligands prepared using the condensation of N,N'-bis(3-aminopropyl)ethylenediamine and 5- or 3,5-substituted salicylaldehyde, has been synthesized. Variable temperature single-crystal X-ray diffraction, magnetic, spectroscopic, electrochemical, and spectroelectrochemical analyses, and theoretical calculations have been used to explore the role of various ligand substituents in the spin-state switching behavior of the prepared manganese(III) complexes. All five complexes consist of an analogous distorted octahedral monocationic MnN4O2 surrounding offered by the flexible hexadentate ligand and ReO4- as the counter anion. However, a disordered water molecule was detected in complex 4. Complexes 1 (X = 5 Cl) and 5 (X = 5 NO2) show gradual and complete spin-state switching between the high-spin (HS) (S = 2) and the low-spin (LS) (S = 1) state with T1/2 values of 146 and 115 K respectively, while an abrupt and complete transition at 95 K was observed for complex 2 (X = 5 Br). Alternatively, complex 3 (X = 3, 5 Cl) exhibits an incomplete and sharp transition between the HS and LS states at 104 K, while complex 4 (X = 3, 5 Br) (desolvated) remains almost LS up to 300 K and then displays gradual and incomplete SCO at a higher temperature. The nature of the spin-state switch and transition temperature suggest that the structural effect (cooperativity) plays a more significant role in comparison with the electronic effect coming from various substituents (Cl, Br, and NO2), which is further supported by the detailed structural, electrochemical, and theoretical studies.

Biologically important 26-32-membered macrocyclic complexes of manganese (II): In situ one pot template synthesis (IOPTS), characterization and bio-efficacy

Twenty six to thirty two membered tetraazamacrocyclic complexes of manganese (II) have been synthesized by template condensation of MnCl2.4H2O with dicarboxylic acid (malonic, succinic, glutaric or adipic acid) and 1,8-diaminooctane in 1:2:2 molar ratios. The new products with octahedral geometry have been characterized by elemental analyses, molecular weight determinations, molar conductance, magnetic moment and spectral studies viz., infrared and electronic. On the basis of the spectral studies the binding sites are proposed as the nitrogen atom of the macrocycles. The formulation of the complexes as [Mn(Macn)Cl2] (where n = 1 - 4) has been established on the basis of chemical composition. To assess the growth inhibiting potential of the manganese (II) complexes biological screening has been undertaken.

COORDINATION BEHAVIOUR AND COMPUTATIONAL STUDIES OF 3-FORMYL CHROMONE N(4)-METHYL-N(4)- PHENYLTHIOSEMICARBAZONE AND ITS TRANSITION METAL COMPLEXES

This article reports on the 3-formylchromone N(4)-substituted thiosemicarbazone’s coordination behavior towards transition metal ions. CHNS analysis, magnetic moment, thermal analysis, IR, UV, NMR, and EPR spectroscopy were used to characterize the compounds. Moreover, DFT, insilico ADME, and docking studies of the ligand were done. Based on the spectral results, copper, cobalt, and nickel complexes had square planar geometry. Conversely, the manganese complex has octahedral geometry. The Gaussian 09 program is utilized for DFT studies. The GLIDE program was used for docking calculations. As receptor molecules, histone deacetylase, ribonucleotide reductase, and DNA methyltransferase were chosen. The SwissADME tool was used to evaluate the pharmacokinetics of the ligand. Based on Lipinski's rules, the estimation of insilico ADMET discovered that ligands procure significant drug-likeness characteristics. Its ability to block histone deacetylase 8 (PDB ID 1T69) protein is shown by docking calculations, and its proper action can be further confirmed in wet lab tests.