Dioxomolybdenum Complexes Research Articles

Selective Photo-epoxidation of (R)-(+)- and (S)-(−)-Limonene by Chiral and Non-Chiral Dioxo-Mo(VI) Complexes Anchored on TiO2-Nanotubes

Selective epoxidation of the (R) and (S) isomers of limonene by dioxomolybdenum(VI) complexes anchored covalently on TiO2 nanotubes using UV–Vis light and O2 as the oxidizing agent was evaluated. It is interesting to study the effect of the ligands: bipyridine, terpyridine, and Schiff base on the stereoselective epoxidation of limonene through photostimulated oxygen atom transfer (OAT). OAT activity observed to increase in the following order: Mo(VI)O2(Schiff base)/TiO2-NT < Mo(VI)Cl2O2 (bipyridine)/TiO2-NT < Mo(VI)Cl2O2(terpyridine)/TiO2-NT. Moderate diastereoselectivity to the cis-isomer of complexes with “non-chiral” ligands like bipyridine and terpyridine was displayed. Contrary to the complex with the Schiff base as “chiral” ligand, it showed an increase in diastereoisomeric excess (52%), associated to an asymmetric double induction, assuming a complex metal-oxo sideway interaction with the trisubstituted olefins at the transition state.

Synthesis and biological potentials of dioxomolybdenum(VI) complexes with ONS and ONN chelating thiosemicarbazones: DNA-binding, antioxidant and enzyme inhibition studies

In this study dioxomolybdenum (VI) complexes of 5-methoxysalicylidene N- or S-alkyl substituted thiosemicarbazones {where alkyl is N-methyl (L1), N-octyl (L2), S-methyl (L3) or S-octyl (L4)} were synthesized, characterized by different spectroscopic techniques (UV, IR, 1H NMR). The structure of the complex with S-methyl-substituted thiosemicarbazone (complex 3) was also determined by X-ray diffraction method. The compounds were evaluated for their antibacterial, antioxidant, anticholinesterase, antidiabetic, and DNA interaction potentials. K. pneumonia was more potently inhibited by ligand L3 (29 ± 0.025 mm zone of inhibition) while E. coli and S. typhi by complex 2 with zone of inhibition of about 28 ± 0.082 and 26 ± 0.245 mm respectively. Complex 2 more potently scavenged DPPH free radical with IC50 of 231 μg/mL while ABTS by ligand L1 (IC50 = 350 μg/mL). Complex 4 with S-octyl was found to have high percent inhibition of acetylcholinesterase with IC50 of 104 μg/mL. Complex 4 strongly inhibited α-amylase with an IC50 value of 153 µg/ml while ligand L4 with IC50 value of 285 µg/ml was more potent inhibitor of α-glucosidase. DNA interaction studies revealed the noncovalent interaction of these compounds with DNA. Highest binding constant among these compounds was recorded for ligand L2 with blue shifts and hyperchromism while lowest for L3.

Studies of some dioxo molybdenum (VI) complexes of a polydentate ligand

Four dioxomolybdenum (VI) complexes of a polydentate ligand derived from Isatin and o-Phenylene Diamine (PDAI) were synthesized and characterized on the basis of different physico chemical methods. Thermal stability of one of the complexes was revealed from its thermal study. Antibacterial activities of the ligand, PDAI and one of its complexes were measured at different concentrations and none of them was found to be active towards S. aureus ATCC 25923 and E. coli ATCC 25922. On the basis of the various physico chemical studies, a distorted octahedral geometry is suggested for all the dioxomolybdenum (VI) complexes.

Incorporation of a dioxo-molybdenum (VI) complex into a titanium-functionalized Zr(IV)-Based metal-organic framework

Abstract The use of Titanium-based Metal-Organic Frameworks (MOFs) as substitutes for titanium dioxide in photocatalytic applications is a recent topic of study. A promising approach is to perform a titanium exchange within a zirconium-based MOF to build a material that combines the properties of the two metals, high thermal stability, and photoactivity. In this work, a novel Zr/Ti MOF that incorporated a dioxo-molybdenum (VI) complex was successfully prepared using two post-synthetic steps. First, a molybdenum complex was anchored to a bipyridine-dicarboxylate linker of a UiO-67 type MOF. Second, a Ti4+ ion exchange for Zr4+ at the zirconium MOF nodes was performed. The as-prepared samples were characterized by PXRD, TGA, FT-IR, N2 adsorption, XPS, SEM and UV–vis in diffuse reflectance mode. The introduction of titanium changed the optical properties of UiO-67 adding advantages through the TiO2 moieties attached to its structure. This was attributed to the metal exchange and the formation of oxo-bridged hetero-Zr-Ti clusters with some loss of crystallinity. Additionally, the addressed surface characterization showed that dioxo-molybdenum (VI) and titanium were incorporated into the structure of Zr-MOF with a small decrease in the surface BET area.

Dioxomolybdenum complex as an efficient and cheap catalyst for the reductive depolymerization of plastic waste into value-added compounds and fuels

Several types of PCL, PLA, PDO, PET and PBT plastic waste were efficiently converted into value-added compounds and fuels catalyzed by MoO2Cl2(H2O)2.

The vital role of ditopic N–N bridging ligands with different lengths in the formation of new binuclear dioxomolybdenum(vi) complexes: synthesis, crystal structures, supramolecular framework and protein binding studies

Role of bis-(pyridyl) and bis-(imidazole) auxiliary ligands in the formation of supramolecular architectures and BSA binding with new binuclear dioxomolybdenum(vi) complexes.

Influence of the pendant arm in deoxydehydration catalyzed by dioxomolybdenum complexes supported by amine bisphenolate ligands

Molybdenum complexes devoid of a strongly coordinating pendant arm result in enhanced catalytic activity.

Cis- and trans molybdenum oxo complexes of a prochiral tetradentate aminophenolate ligand: Synthesis, characterization and oxotransfer activity

Reaction of [MoO2Cl2(dmso)2] with the tetradentate O2N2 donor ligand papy [H2papy = N-(2-hydroxybenzyl)-N-(2-picolyl)glycine] leads to formation of the dioxomolybdenum(VI) complex [MoO2(papy)] (1) as a mixture of cis and trans isomers. Recrystallization from methanol furnishes solid cis-1, whereas the use of a dichloromethane-hexane mixture allows for the isolation of the trans-1 isomer. Both isomers have been structurally characterized by X-ray crystallography and the energy difference between the isomeric pair has been investigated by electronic structure calculations. Optimization of two configurational isomers in the gas phase predicts the trans isomer to lie 2.5 kcal/mol lower in energy (ΔG) than the cis isomer, which is inconsistent with the solution NMR data in d3-MeCN that exhibit a Keq of ca. 3 at 298 K for the trans ⇌ cis equilibrium. The DFT-computed energy difference is significantly improved (Keq = 5.4) by the inclusion of the MeCN solvent using the polarization continuum model (PCM). Density functional calculations reveal that the isomerization proceeds via a Ray-Dutt twist mechanism with a barrier of 14.5 kcal/mol, which is in accordance with the 1H NMR spectral data and the rapid equilibration of these isomers in solution. The catalytic reactivity of [MoO2(papy)] in the epoxidation of cis-cyclooctene is described, as well as its ability to effect oxo transfer from DMSO to PPh3.

Molecular and Inner Complex Compounds of Dioxomolybdenum(VI) with Disubstituted Salicydenealcoholimines: Crystal Structure of 1 : 1 Dioxo(3,5-Dibromosalicylidenemonoethanoliminato)molybdenum(VI) Solvate with Methanol [MoO2(L1) · MeOH] (L1 = C9H7Br2NO2)

Complexes of dioxomolybdenum(VI) of the molecular (МоО2Сl2 · 2H2L) and inner complex ([MoO2L · Solv]) types are synthesized (H2L are azomethines, derivatives of disubstituted R1,R2-salicylaldehydes (R1, R2 = 3.5-Вr2; R1 = 3-МеО, R2 = 5-Вr) and monoethanolamine; Solv is a methanol, dimethylformamide, pyridine, or α-picoline molecule). The cis-octahedral structure of the complexes is concluded on the basis of the IR spectroscopic data. In the molecular compounds, the ligands are coordinated via the O atom of the carbonyl group of the H2L tautomeric form. In the inner complex compounds, the ligands are coordinated in the deprotonated benzoid form. The structure of [MoO2(L1) · МеОН] (I) (where L1 is C9H7Br2NO2) is determined by X-ray diffraction analysis (СIF file CCDC no. 1898088). In the mononuclear molecule of compound I, the Mo atom has the octahedral coordination by two oxo ligands, two oxygen atoms, the nitrogen atom of the tridentate bis(chelate) two-charge ligand (L1)2–, and the O atom of the methanol molecule. The neutral N(1) and O(1) atoms of the L1 and МеОН ligands, respectively, are arranged in the trans positions to the O(oxo) ligands. The Mo–N(1) (2.265 A) and Мо–О(1) (2.372 A) bonds are substantially elongated due to the structural manifestation of the trans effect of the multiply bonded oxo ligands. The intermolecular hydrogen bonds (МеОН)О–Н···О(oxo) join the molecules into supramolecular 1D chains.

SYNTHESIS AND STUDIES OF SOME cis- MoO2(VI) COMPLEXES WITH NITROGEN DONOR MACROCYCLIC LIGANDS

According to what mention in research paper, the reaction of [MoO 2 (L)](acac) 2 with 1,3-diketones gives the formation of 1 MoO 2 (VI) complex of formulation [MoO 2 (L)](acac) 2 with a Schiff base, acquire from condensation of di-2-thienylethanedione with 2,3-diaminotoluene and four new complexes having formula [MoO 2 (ML)](acac) 2 . The each of the five dioxomolybdenum(VI) complexes synthesized were represented by thermal studies, elemental analyses, UV-Vis, molar conductance, IR and NMR and. The molybdenum metal has coordination number of 6. Each of the dioxomolybdenum(VI) complexes have geometry of octahedral arrangement. Distorted octahedral environment exist surrounding to molybdenum element in formed MoO 2 (VI) complexes. The ligand geometry was completed by two oxo O-atoms and four N-atoms. The synthesized complexes were show moderate activity versus S. aureus and S. typhi. The advancement inside the antibacterial activity being defined on the idea of chelation speculation.

Oxovanadium(V) and Dioxomolybdenum(VI) Complexes of Amide-Imine Conjugates: Structures, Catalytic and Antitumor Activities.

Three new amide-imine conjugates, namely [(E)-2-hydroxy-N'-((2-hydroxynaphthalen-1-yl)methylene)benzohydrazide] (SALNP), [(E)-N'-(4-(diethylamino)-2-hydroxybenzylidene)-2-hydroxybenzohydrazide] (SALSD), and [(E)-N'-(3-ethoxy-4-hydroxybenzylidene)-2-hydroxybenzohydrazide] (SALVN), derived by reacting 2-hydroxybenzohydrazide (SAL) with three different aldehyde, 2-hydroxynapthaldehyde, 4-(diethylamino)-2-hydroxybenzaldehyde, and 3-ethoxy-4-hydroxybenzaldehyde, respectively. Three mononuclear oxovanadium(V) and two μoxo-bridged dinuclear molybdenum(VI) complexes have been synthesized using SALNP and SALSD. Besides, SALVN is used to prepare oxovanadium(V) and dioxomolybdenum(VI) complexes. All five metal complexes along with three amide-imine conjugates are characterized by single crystal XRD analysis. Some of them have been explored as catalyst for oxidation of alkyl benzene and styrene. Antitumor activities of the metal complexes along with ligands have been studied on Dalton lymphoma (DL) and 2PK3 murine lymphoma cells.

Synthesis, Crystal Structures, and Catalytic Properties of Dioxomolybdenum(VI) Complexes Derived from 4-Chloro-2-{[4-Diethylamino-2-Hydroxybenzylidene]amino}phenol

Two new dioxomolybdenum(VI) complexes, [MoO2L(EtOH)] (I) and [MoO2L(Sal)] (II), where L is the dianionic form of 4-chloro-2-{[4-(diethylamino)-2-hydroxybenzylidene]amino}phenol (H2L), Sal is 4-diethylaminosalicylaldehyde, were prepared and characterized by IR and UV-Vis spectra, as well as single crystal X-ray diffraction (CIF files CCDC nos. 1849408 (I) and 1849409 (II)). Complex I crystallizes as the triclinic space group $$P\bar {1}$$ with unit cell dimensions a = 7.3050(10), b = 11.6969(16), c = 13.3433(19) A, α = 103.915(2)°, β = 102.542(2)°, γ = 105.676(2)°, V = 1015.8(2) A3, Z = 2, R1 = 0.0616, wR2 = 0.1579, GOOF = 1.080. Complex II crystallizes as the triclinic space group $$P\bar {1}$$ with unit cell dimensions a = 7.0773(11), b = 12.8817(12), c = 16.420(2) A, α = 107.000(2)°, β = 101.478(2)°, γ = 91.416(2)°, V = 1397.4(3) A3, Z = 2, R1 = 0.0484, wR2 = 0.1048, GOOF = 1.015. X-ray analyses indicate that the complexes are dioxomolybdenum(VI) species with the Mo atoms in octahedral coordination. The catalytic oxidation property of the complexes with tert-butylhydroperoxide in CH2Cl2 was studied.

Synthesis and Structural Studies on some Dioxomolybdenum (VI) Complexes Bearing 1-(1-Hydroxynaphthalen-2-yl) Ethanone Moiety

A number of new molybdenum complexes Cis-MoO2 (NE)2 .CH3 OH, Cis-MoO2 (HRSB)2 .nH2 O {R= H, 4-Br, 4-OCH3 , 4-CH3 and n= 0, 1, 2} Cis-MoO2 (HL)(acac).nH2 O {HL= HNEBH, HNEINH, HNENH, HNEPH, n=0, 1}, Cis-[MoO2 (L\)2 .nH2 O], {L\= HNE-2-ABH, HNE-4-ABH, n = 0, 2} and Cis-[Mo2 O5 (HNEAH)2 ] have been synthesized and characterization by magnetic, spectroscopic (FT-IR, 1H and 13C-NMR spectra) and electrochemical techniques. The complexes were made reaction of Cis-MoO2 (acac)2 with the ligands, (1-hydroxynaphthalen-2-yl)ethenone (HNE), (E)-2-(1-(phenylimino)ethyl)naphthalen1-ol (HASB), (E)-2-(1-(p-tolylimino)ethyl) naphthalen-1-ol (HTSB), E-2-(1-(4-methoxyphenylimino)ethyl)naphthalen-1-ol (HMSB) and (E)-2-(1-(4-bromophenylimino)ethyl)naphthalen-1-ol (HBrSB) monobasic bidentate (NO) or 2-anmino-N/- (1-(1-hydroxynaphthalene-2-yl)ethylidene)benzohydrazide (HNE2-ABH), 4-anmino-N/-(1-(1-hydroxynaphthalene-2-yl) ethylidene)benzohydrazide (HNE4-ABH), N/-(1-(1-hydroxynaphthalene-2-yl)ethylidene)benzohydrazide (HNEBH), N-(1-(1-hydroxynaphthalene-2-yl)ethylidene)acetohydrazide (HNEAH), N/-(1-(1-hydroxynaphthalene-2-yl)ethylidene) nicotinohydrazide (HNENH), N/-(1-(1-hydroxynaphthalene-2-yl)ethylidene)isonicotinohydrazide (HNEINH), N/-(1- (1-hydroxynaphthalene-2-yl)ethylidene)picolinohydrazide (HNEPH), they coordinate as dibasic tridentate (OON). Both the molecular and the spectroscopic studies showed that, the complexes are octahedrally coordinated. The redox properties, of the electrode couples and the stability of some complexes towards reduction were linked to the electron withdrawing or ability releasing of the substituent in the Schiff bases and the hydrazones. Results show that, changes in E1/2 for the complexes due to remote substituent effects could be related to changes in basicity of the carbonyl oxygen of the hydrazide moiety in the hydrazone ligand. The electron-donating substituents stabilized Mo(VI) complexes while electron-withdrawing groups favored lower oxidation state of Mo(V) and/ or Mo(IV) species. The nature of mechanism and kinetic parameters of the electroactive chelates are strongly dependent on the substituent. The EHOMO and ELUMO level, of hydrazone and some of Cis-molybdenum complexes, from both electrochemical and theoretical data also backdonation energy (ΔEback-donation), ionization potential (I), molecular dipole moment (μ), electronegativity (χ), softness (σ) electron affinity (A), global hardness (η), and electrophilicity index (ω) were calculated.

Synthesis and Crystal Structure of a Dioxomolybdenum(VI) Complex Derived from 2-Bromo-N'-(3,5-dichloro-2-hydroxybenzylidene)benzohydrazide with Catalytic Epoxidation Property

A dioxomolybdenum(VI) complex [MoO2L(EtOH)] (I), derived from the hydrazone ligand 2‑bromo-N'-(3,5-dichloro-2-hydroxybenzylidene)benzohydrazide has been prepared and characterized by physico-chemical and spectroscopic methods, as well as single crystal X-ray diffraction (CIF file CCDC no. 1840671). The hydrazone ligand coordinates to the Mo atom through the phenolate oxygen, imino nitrogen, and enolic oxygen. The Mo atom is six-coordinate in an octahedral geometry. Complex I shows high catalytic activity and selectivity in the epoxidation of cyclohexene with tert-butylhydroperoxide as primary oxidant.

Dioxomolybdenum(VI) complexes with 3-methoxy salicylidene-N-alkyl substituted thiosemicarbazones. Synthesis, characterization, enzyme inhibition and antioxidant activity

3-methoxysalicylidene N-alkyl-thiosemicarbazones (L) (where alkyl is propyl, butyl, pentyl or hexyl) were synthesized. The reaction of the ONS donor ligands with [MoO2(acac)2] in methanol yielded the mixed ligand complexes bearing a solvent molecule as co-ligand, [MoO2(L)MeOH)]. The ligands and complexes were characterized by using analytical and spectroscopic methods. As a representative sample, the dioxomolybdenum(VI) complex of the N4-butyl-substituted thiosemicarbazone was crystallographically examined to ensure the expected structures. X-ray data showed a distorted octahedral environment of molybdenum center. Tyrosinase, collagenase inhibition and antioxidant properties of the compounds were investigated using spectroscopic methods. The ligand and complexes exhibited the different inhibitory activities depending on N-alkyl substituents. Similarly, also the antioxidant capacity of the compounds changed in relation to the substituents.

New homochiral and heterochiral Mo(VI) complex from racemic ligand: Synthesis, X-ray structure, diastereomers separation and biological activities

A diastereomeric pair (homochiral and heterochiral) of Schiff base dioxo molybdenum complex was synthesized using chiral ligand (HL: R/S-1-((naphtalen-3-yl)methylenamino)propan-2-ol) in racemic form. Then, to separation of this diastereomeric pair, crystallization method was proposed which was successful with acetonitrile. 1H NMR technique was used to confirm the results. The complexes thoroughly characterized using FT-IR, elemental analysis, 1H NMR and 13C NMR techniques, and MoO2L(LH2)1 has been structurally characterized using single-crystal X-ray diffraction. The cytotoxic activity of the new compounds has been evaluated using MCF-7 (human breast adenocarcinoma) and HeLa (human cervix adenocarcinoma), in addition to normal human fibroblast cells using the MTT cytotoxicity assay. Compounds MoO2L(LH2)1 and MoO2L(LH2)2 revealed IC50 values 18 µM and 37 µM on MCF-7 and 58 µM and 17 µM on HeLa, respectively. MoO2L(LH2)2 showed high selectivity (3–13 folds) for cancerous cells over normal cells, as the maximum cell mortality of 8.77%. Furthermore, The HSA- and DNA-binding of the Mo(VI) complexes were investigated by absorption, emission spectroscopy, viscosity measurements and molecular docking. Their binding constant are calculated as: HSA-binding of MoO2L(LH2)1 is 6.7 × 104 M−1 and of MoO2L(LH2)2 is 5.8 × 104 M−1, while their DNA-binding are 5.6 × 104 M−1 and 2.2 × 105 M−1, respectively. Their thermodynamic parameters were also determined at different temperatures.

Synthesis and characterization of new thiosemicarbazonato molybdenum(VI) complexes and their in vitro antimicrobial activities

Eight new mixed ligand complexes of dioxomolybdenum(VI) with 2-hydroxy-3-methoxy/3,5-dibromo benzaldehyde 4-phenyl/ethyl-S-methyl/butyl thiosemicarbazones (L) were synthesized. The complexes of general formula [MoO2LD] (D: methanol, pyridine) were characterized by elemental analysis, IR, UV, and 1H-NMR spectroscopy. The structure of 3a was also determined by X-ray single-crystal diffraction. The thiosemicarbazone ligands are coordinated to dioxomolybdenum(VI) center through ONN set and the sixth coordinated site of the molybdenum is occupied by the second ligand (D). The in vitro antimicrobial activities of all thiosemicarbazones and their dioxomolybdenum(VI) complexes were tested against Candida albicans, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus.

Synthesis, characterization and anticandidal activity of dioxomolybdenum(VI) complexes of the type [MoO2{ON=C(CH3)Ar}2] and [MoO2{OC(R)CHC(R’)=NC6H5}2

Interaction of [MoO2(acac)2] with internally functionalized oximes like HON=C(CH3)Ar (Ar = C4H3S, C4H3O or C5H4N) and Schiff's Bases derived from β – diketones like HOC(R)CHC(R′)=NC6H5 (R = R’ = CH3 or C6H5; R = CH3 and R’ = C6H5) led to the formation of yellow dioxomolybdenum(VI) complexes of the type [MoO2{ON=C(CH3)Ar}2] and [MoO2{OC(R)CHC(R′)=NC6H5}2]. Oximes were synthesized by green methodology. The newly synthesized complexes were characterized on basis of elemental analysis and various spectral findings.Anticandidal activity of [MoO2{ON=C(CH3)C6H4N}2] clearly reveals that the complex is biologically active against fungal diseases.

Polyethyleneimine Nanofibers Functionalized with Tetradentate Schiff Base Complexes of Dioxomolybdenum(VI) as Efficient Catalysts for Epoxidation of Alkenes

AbstractThree tetradentate Schiff base ligands (H2L1‐3) were prepared from the reaction of 5‐sustituted‐2‐hydroxybenzaldehydes and 3,4‐diaminobenzoic acid. The obtained ligands were reacted with molybdenyl acetylacetonate in ethanol to prepare the corresponding dioxomolybdenum(VI) complexes (MoO2L1‐3) in good yields (80‐82%). Immobilization of the abovementioned complexes on polyethyleneimine (PEI) was achieved via condensation of carboxylic functional groups of the complex with amine functional groups of the polymer in presence of dicyclohexylcarbodiimide (DCC) and 4‐dimethylaminopyridine (DMAP). The obtained hybrid materials were then converted to electrospun nanofibers and used as recyclable catalysts for the epoxidation of alkenes.

Structural Features of Mononuclear Chelate Dioxomolybdenum(VI) Complexes with Tetradentate Chelate Ligands—Schiff Bases, Salicylaldehyde Derivatives [MOO2(Lm)] (m = 1−11)

The structural features of 12 chelate complexes with the general formula [MoO2(Lm)], where Lm is a tetradentate chelate (N, N, O, O) ligand representing a Schiff base, a salicylaldehyde derivative (m = 1−11), have been considered. In all 12 complexes, the molybdenum atom has a cis,cis,cis-octahedral coordination. Both pairs of N(Lm), O(Lm) atoms occupy both trans- and cis-positions to oxo ligands.