Dioxomolybdenum Complexes Research Articles

Expeditious and selective synthesis of 2,4,5-trialkyl-1H-imdazoles and benzimidazoles via multicomponent one-pot reaction catalyzed by Schiff base dioxomolybdenum(VI) complex

Imidazoles and benzimidazoles are privileged heterocyclic compounds that can be extensively found in medicinal and materials chemistry, however, the experimental procedures for their synthesis are limited to multicomponent condensation reactions and normally are strongly dependent upon the desired substitution pattern, consequently several procedures with different conditions and catalysts are available in literature. Accordingly, the development of synthetic methodologies to afford these compounds remains a very attractive research problem. In this regard, dioxomolybdenum based catalysts are emerging as versatile and non-expensive reagents for a myriad of chemically relevant transformations. Within this context, an expedient and efficient synthesis of 2,4,5-trialkyl-1H-imidazoles and benzimidazoles from a multicomponent one-pot condensation has been developed with a tridentate Schiff base dioxomolybdenum(VI) complex, resulting in an efficient, simple and readily available catalyst to promote the aforementioned reaction. This reaction offers advantages such as good to excellent yields, good selectivity of products, low catalyst loadings and simple reaction work-up.

Structural elucidation of the dichloridodioxido-[(4,7-dimethyl)-1,10-phenanthroline]molybdenum(VI) (C14H12Cl2MoN2O2)

In this work, the synthesis, characterization, and X-ray powder diffraction data for dichloridodioxido-[(4,7-dimethyl)-1,10-phenanthroline]molybdenum(VI) are reported. The crystal structure of this compound was solved from powder diffraction data using the simulated annealing method with a subsequent refinement using the Rietveld method. The dioxo-molybdenum (VI) complex C14H12Cl2MoN2O2 crystallizes in a monoclinic system with space group C2/c (N° 15) with refined unit-cell parameters a = 12.9495 (5) Å, b = 9.7752 (4) Å,c = 12.0069 (6) Å, β = 101.702 (3) °, unit-cell volume V = 1488.27 (11) Å3, and values of Z′ = 0.5 and Z = 4. The molecules are organized into chains diagonally along the a and c axis. Parallel polyhedra are observed along these axes formed by the interactions of Mo, Cl, O, and N atoms present in the coordination sphere. The crystalline packing of this dioxo-molybdenum (VI) complex is dominated by five intermolecular hydrogen bonds, two intramolecular hydrogen bonds, and the four interactions between the centroids (CgI⋯CgJ) of the aromatic rings. An analysis of the Hirshfeld surface revealed that the greatest contributions of the attractive forces are given by H⋯Cl/Cl⋯H, H⋯C/C⋯H, H⋯O/O⋯H, and H⋯H interactions.

Thiosemicarbazone-based Dioxomolybdenum (VI) complexes as inorganic nucleases

This study focuses on the design of alkyl-substituted thiosemicarbazones from 5-bromosalicylaldehyde and substituted thiosemicarbazides and the corresponding dioxomolybdenum(VI) complexes, hitherto unreported. In addition to elemental analyses, the synthesized ligands and the corresponding complexes are further analyzed by physico-chemical and spectroscopic techniques. The DNA interaction studies are based on UV absorption titration and gel electrophoretic methods. The binding constants (Kb) for the ligands (L1-L4) are found to be 1.20 ± 0.1 × 104 M−1; 1.32 ± 0.2 × 104 M−1; 1.27 ± 0.3 × 104 M−1 and 1.25 ± 0.3 × 104 M−1 respectively and that of the complexes (C1–C4) are 1.45 ± 0.2 × 104 M−1; 2.10 ± 0.4 × 104 M−1; 1.54 ± 0.2 × 104 M−1 and 2.13 ± 0.2 × 104 M−1, respectively. The complexes have shown relatively higher binding propensity as compared to that of the ligands. Further, as the outcome of gel electrophoresis studies, the ligands show a cleavage pattern of nicked circular (Form I). However, the complexes show cleavage patterns of both nicked circular and supercoiled, Forms I & II respectively. This implies that both the ligands and complexes possess varying binding efficacy with DNA and accordingly the cleavage patterns also differ.

Photo-assisted selective oxidation of monoterpenes by a covalently supported dioxo-molybdenum complex on TiO2: Effect of electron donor ligands

High-valent dioxo-Mo species have demonstrated the ability to catalyze industrially interesting alkene-to-epoxide transformations via oxygen atom transfer (OAT) reactions. The impact of electron donor ligands of dioxo-molybdenum complexes [MoO2Ln] covalently supported on TiO2 nanotubes (MoO2Ln/TiO2NT) on OAT to α-pinene, β-pinene, (R)-limonene and camphene has been investigated through the use of UV–vis radiation and molecular oxygen. Molybdenum complexes with electron donor ligands, such as bipyridine, bispyrazole, and terpyridine, exhibited high conversion and selectivity towards epoxide formation. This suggests that electron donation enhances the efficiency of photostimulated OAT. The photonic efficiency (ξ) demonstrates a linear correlation between the ligand structure and the OAT activity, indicating that the electron donation of the ligands enhances electron mobility towards the Mo=O bond. This correlation is evident in the position of the IR and Raman νsym(O=Mo=O) and vasym(O=Mo=O) vibrations of the complex Mo.

Efficient and Convenient One-pot Synthesis of Quinoxalines Promoted by Schiff base dioxomolybdenum(VI) complex

Schiff base dioxomolybdenum(VI) complex was found to be an effective catalyst for the condensation reaction of benzoins and 1,2-diamines to afford quinoxalines in one-pot reaction. The route provides several advantages such as simple process, mild conditions, low catalyst loadings and environmental friendliness.

Binuclear Dioxomolybdenum(VI) Complex Based on Bis(2-pyridinecarboxamide) Ligand as Effective Catalyst for Fuel Desulfurization

A binuclear dioxomolybdenum catalyst [(MoO2Cl2)2(L)] (1) (with L (1S,2S)-N,N′-bis(2-pyridinecarboxamide)-1,2-cyclohexane) was prepared and used as catalyst for the desulfurization of a multicomponent model fuel containing the most refractory sulfur compounds in real fuels. This complex was shown to have a high efficiency to oxidize the aromatic benzothiophene derivative compounds present in fuels, mainly using a biphasic 1:1 model fuel/MeOH system. This process conciliates catalytic oxidative and extractive desulfurization, resulting in the oxidation of the sulfur compounds in the polar organic solvent. The oxidative catalytic performance of (1) was shown to be influenced by the presence of water in the system. Using 50% aq. H2O2, it was possible to reuse the catalyst and the extraction solvent, MeOH, during ten consecutive cycles without loss of desulfurization efficiency.

Molybdenum catalysts based on salan ligands for the deoxydehydration reaction

Ligand effects have been evaluated in deoxydehydration (DODH) catalyzed by dioxomolybdenum complexes of salan ligands.

Dioxomolybdenum(VI) complexes of 2-hydroxy-4-benzyloxybenzaldehyde thiosemicarbazones alkylated via N or S atoms. Synthesis, characterization, antioxidant and xanthine oxidase inhibition performance

Using the synthesis method, we produced a series of 2‑hydroxy-4-benzyloxybenzylidene N- or S-alkyl chains substituted thiosemicarbazones and their dioxomolybdenum(VI) complexes containing long alkyl chains (pentyl, hexyl, heptyl, and octyl). A series of dioxomolybdenum(VI) complexes with 2‑hydroxy-4-benzyloxybenzylidene thiosemicarbazones substituted by long alkyl chains, pentyl, hexyl, heptyl, and octyl, on the N- or S atoms were synthesized. Analytical and spectroscopic techniques were used to characterize the compounds. As a representative molecule, the molecular structure of complex I named cis-dioxo-(N1–2‑hydroxy-4-benzyloxybenzylidene-N4-pentylthiosemicarbazonato)-methanol-molybdenum(VI) was identified by single crystal X-ray diffraction. Using the method of cupric reducing antioxidant capacity, the ONN donor thiosemicarbazones (LV-LVIII) were found to have higher trolox equivalent antioxidant capacity values than those with ONS (LI-LIV). Furthermore, the inhibitory activities of xanthine oxidase and the scavenging effects of the compounds on the hydroxyl radical were examined. Complex VII was the most effective XO inhibitor with an IC50 value of 33.41 μM in similar to allopurinol as a potential XO inhibitor (IC50: 33.14 μM), and it can be used as XO inhibitor in treatment of XO-based disorders.

Cis-dioxomolybdenum(VI) complex bearing tridentate ONO isonicotinoyl hydrazone Schiff base: Synthesis, characterization, crystal structure, and catalytic activity investigation for the oxidation of sulfides

A cis-dioxomolybdenum Schiff base complex, MoO2(L)(CH3OH), has been synthesized by reacting MoO2(acac)2 with isonicotinic acid hydrazide in refluxed methanol. The synthesized dioxomolybdenum complex was characterized by elemental analysis and diverse spectroscopic methods, for example, UV-Vis, FT-IR, and 1H and 13C NMR. The single crystal X-ray diffraction technique was used to determine the structure of the complex, which indicates that Mo(VI) ion is hexa coordinated and adopts a distorted octahedral coordination geometry on complexation. The synthesized complex is novel for its catalytic potential for the oxidation of aryl and alkyl sulfides under refluxing conditions in the presence of hydrogen peroxide and ethanol. This method generates the required sulfoxides and sulfones with high yields in short intervals of time.

Crystal and Molecular Structure of the Island Tetranuclear Dioxomolybdenum(VI) Complex [MoO2(L1)]4 (H2L1 Is Acetylacetone Isonicotinoylhydrazone) with Large Intra- and Intermolecular Channels

Crystal and Molecular Structure of the Island Tetranuclear Dioxomolybdenum(VI) Complex [MoO2(L1)]4 (H2L1 Is Acetylacetone Isonicotinoylhydrazone) with Large Intra- and Intermolecular Channels

Molybdenum catalyzed deoxydehydration of aliphatic glycols under microwave irradiation

The effectiveness of microwave irradiation in promoting the deoxydehydration of aliphatic diols using dioxomolybdenum catalysts has been evaluated. The commercially available molybdenum precursor MoO2(acac)2 was found to be a superior catalyst as compared to dioxomolybdenum complexes stabilized by aminebisphenol ligands under these conditions. Octane-1,2-diol and decane-1,2-diol were converted to the corresponding olefins in 40−53% yields in 40 mins at 220−230 οC; this is a significant reduction in reaction time and higher activity when compared to reactions performed using conventional heating. More importantly, a similar yield (48%) of 1-decene could be achieved within 10 mins from a reaction carried out at 250 οC.

Protein binding studies and antioxidant activities of two mononuclear dioxomolybdenum(VI) complexes with 2-(3-methyl-5-phenyl pyrazol-1-yl) benzthiazole

Two yellow air-stable mononuclear dioxomolybdenum(VI) complexes, MoO2Cl2L (1) and MoO2Br2L (2) [where L = N,N donor ligand 2-(3-methyl-5-phenyl pyrazol-1-yl) benzthiazole], have been synthesized from their parent oxomolybdenum(V) complexes in dichloromethane. The binding affinity and binding mode of the molybdenum complexes with bovine serum albumin (BSA) have been explored by absorption and fluorescence titrations and time resolved fluorescence measurements. The number of binding sites for the complexes is nearly equal to unity, indicating there is only one binding site per BSA molecule. Molecular docking studies are also carried out to elucidate the binding mechanism, indicating that the complexes could quench the intrinsic fluorescence of BSA in a static quenching manner. Fluorescence resonance energy transfer study reveals that energy transfer takes place from Tryptophan residue of BSA to the synthesized complexes. The anti-oxidative properties of the complexes are examined by ABTS radical scavenging activities and DPPH radical quenching. The complexes exhibit different activities due to the influence of halogen substitution to the metal ion. MoO2Br2L (2) exhibits better activities than MoO2Cl2L (1) according to their EC50 values.

Silica-coated nanomagnetite-supported dioxomolybdenum(VI) complex: Synthesis, characterization, and catalytic application in the green sulfoxidation

Silica-coated nanomagnetite-supported dioxomolybdenum(VI) complex: Synthesis, characterization, and catalytic application in the green sulfoxidation

Selective synthesis of 2‐substituted 2,3‐dihydroquinazolin‐4(1H)‐ones and quinazolin‐4(3H)‐ones catalyzed by Schiff base dioxomolybdenum(VI) complex

AbstractSchiff base dioxomolybdenum(VI) complex is found to be a novel and efficient catalyst for the selective synthesis of 2‐substituted 2,3‐dihydroquinazolin‐4(1H)‐ones via condensation of 2‐aminobenzamide with aldehydes or ketones. Also, this catalyst is also found to be efficient for the construction of quinazolin‐4(3H)‐ones while in the presence of hydrogen peroxide as oxidant. At higher temperature the aldehydes undergo an oxidative cyclization reaction affording the quinazolin‐4(3H)‐ones. Herein we report a novel protocol with practical simplicity, broad substrate scope, good selectivity, moderate to excellent yields, and low catalyst loading (0.5% mol).

Investigation of spectroscopic, crystallographic, thermal and antioxidant properties of mononuclear dioxomolybdenum(VI) complexes derived from a new symmetric bisthiocarbohydrazone

A new symmetric bisthiocarbohydrazone [1,5-bis(5-allyl-2-hydroxy-3-methoxybenzylidene)thiocarbohydrazone (H2L)] was prepared from the reaction of thiocarbohydrazide with 5-allyl-2-hydroxy-3-methoxybenzaldehyde. Five new solvate dioxomolybdenum(VI) complexes of close formulas [MoO2(L)R-OH] (R: methyl for Mo1, ethyl for Mo2, propyl for Mo3, butyl for Mo4 and pentyl for Mo5) were synthesized by reacting bis(acetylacetonato)dioxomolybdenum(VI) [MoO2(acac)2] with this proligand H2L. The structures of all compounds were verified by IR, UV–vis and 1H NMR spectroscopies, elemental analysis, magnetism and molar conductivity measurings. The solid-state structures of Mo1 and Mo2 were also elucidated using the X-ray crystallography technique. X-ray crystallographic studies indicated that symmetric bisthiocarbohydrazone is coordinated to the cis-MoO22+ ion through sulfur atom, imine nitrogen and phenolic oxygen as the tridentate ONS donor. The sixth coordination of the molybdenum atom, which has distorted octahedral geometry around it, is completed by solvent (R-OH). The thermal characteristics of the compounds were studied by thermogravimetric analysis (TGA). TGA results support the presence of solvent molecules coordinated to molybdenum atoms in the complexes. Antioxidant capacities of the compounds were measured using the CUPric Reducing Antioxidant Capacity (CUPRAC) method. The compounds were also examined for their free radical scavenging activities by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical method. When compared to a standard, Trolox, all of the compounds demonstrated good antioxidant activity.

Synthesis, structural and DFT studies on thiosemicarbazone-based dioxomolybdenum(VI) complexes with co-ligands

5-Chloro-2-hydroxybenzophenone-S-methyl-4-phenylthiosemicarbazone (Η2L1) was synthesized from 4-phenylthiosemicarbazide. Reaction of Η2L1 with [bis(acetylacetonato)dioxomolybdenum(VI)] gave the dioxomolybdenum(VI) complexes with [MoO2(L1)(L2)] composition where L2 is n-pentanol, ethylene glycol monomethyl ether, ethyl acetate, isoamyl alcohol, pyridine, or γ-picoline. The structures of the stable solid complexes were elucidated using elemental analysis, electronic, FTIR, and 1H NMR spectra. Crystallographic analysis of [MoO2(L1)(n-pentanol)] (1) clearly indicated the O,N,N-chelating thiosemicarbazone backbone and the distorted octahedral environment of the molybdenum atom. Complex 1 crystallizes in the monoclinic system with P21/n space group and Z = 4. Moreover, the quantum chemical calculations supporting the experimental data of 1–6 are also reported in this study. Geometric optimization and theoretical vibrational spectra calculations of the complexes were performed by using the B3LYP density functional level of theory with LANL2DZ basis set employing density functional theory (DFT). Also, the non-covalent interaction (NCI) plot index analysis reveals the presence of different kinds of non-covalent interactions in [MoO2(L1)(n-pentanol)] (1).

Biomimetic Oxidation of Sulfides Catalyzed by Polystyrene-Bound Dioxomolybdenum Complex as an Efficient Recoverable Heterogeneous Catalyst

Biomimetic Oxidation of Sulfides Catalyzed by Polystyrene-Bound Dioxomolybdenum Complex as an Efficient Recoverable Heterogeneous Catalyst

Dioxomolybdenum (VI) and oxomolybdenum (IV) complexes with N, O, and S bidentate ligands, syntheses, spectral characterization, and DFT studies

Two dioxomolybdenum (VI) complexes with the chemical formula [MoO2(acac)(HPY)], [MoO2(DTO)(HPY)], and oxomolybdenum (IV) complexes [MoO(acac)(HPY)], [MoO(DTO)(HPY)] have been prepared and characterized by different spectral techniques such as (FTIR, UV-Vis., Mass, 1H NMR) spectra, magnetic susceptibility, and theoretical studies. The ligands used in this study were acetylacetone, 2-hydrazinopyridine, and dithiooximid. The spectroscopic data and the theoretical calculations suggested distorted octahedral structures for the dioxomolybdenum(VI) complexes. The dioxomolybdenum(VI) complexes were diamagnetic. The oxomolybdenum(IV) complexes are paramagnetic and have distorted square pyramidal structures. Theoretical calculations of the free ligands and the prepared complexes have been done by using DFT calculations using (G 09 W) software. The complexes were very stable and their energies ranged from (−708.85 to −921.99 a.u.) whereas the free (HPY) and (DTO) ligands were (−359.06 and −984.54 a.u.), respectively. The prepared complexes are polar (8.11–10.80 Debye) for Mo(VI), and (6.63–13.72 Debye) for Mo(IV). The HOMO orbital energies of the Mo(VI) complexes are (−0.229, and −0.377 a.u.), respectively whereas for the Mo(IV) complexes are (−0.192, −0.318 a.u.), respectively while for the (HPY) and (DTO) ligands are (−0.216, −0.262 a.u.). The LUMO orbitals energies of the Mo(VI) complexes are (−0.124, and −0.247 a.u.) and for the Mo(IV) are (−0.093, −0.208 a.u.), respectively.

Magnetic nanoparticles-supported dioxomolybdenum(VI) complex: An effective reusable heterogeneous nanocatalyst for the green selective sulfoxidation

A dioxomolybdenum(VI) complex with the tridentate ONO Schiff base ligand was derived from the condensation reaction of 3-ethoxysalicylaldehyde with isonicotinohydrazide and then was immobilized on the surface of silica-coated magnetite nanoparticles. The resultant organic–inorganic hybrid material was characterized by infrared spectroscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy, transmission electron microscopy, vibrating sample magnetometry, and X-ray powder diffraction. The catalytic performance of the synthesized nanocatalyst was tested for the selective sulfoxidation of the different sulfides by using H2O2 as a safe oxidizing agent in ethanol as a green solvent under reflux conditions. The heterogeneous catalyst was recovered magnetically and reused at least five times without a notable decrease in its activity.

Crystal structures of two dioxomolybdenum complexes stabilized by salan ligands featuring phenyl and cyclo-hexyl backbones.

Two cis-dioxomolybdenum complexes based on salan ligands with different backbones are reported. The first complex, dioxido{2,2'-[l,2-phenyl-enebis(imino-methyl-ene)]bis-(phenolato)}molybdenum(VI) di-methyl-formamide disolvate, [Mo(C20H18N2O2)O2]·2C3H7NO (PhLMoO2, 1b), features a phenyl backbone, while the second complex, (6,6'-{[(cyclo-hexane-1,2-di-yl)bis(aza-nedi-yl)]bis-(methyl-ene)}bis-(2,4-di-tert-butyl-phenolato))dioxidomolybdenum(VI) methanol disolvate, [Mo(C36H56N2O2)O2]·2CH3OH (CyLMoO2, 2b), is based on a cyclo-hexyl backbone. These complexes crystallized as solvated species, 1b·2DMF and 2b·2MeOH. The salan ligands PhLH2 (1a) and CyLH2 (2a) coordinate to the molybdenum center in these complexes 1b and 2b in a κ2 N,κ2 O fashion, forming a distorted octa-hedral geometry. The Mo-N and Mo-O distances are 2.3475 (16) and 1.9567 (16) Å, respectively, in 1b while the corresponding measurements are Mo-N = 2.3412 (12) Å, and Mo-O = 1.9428 (10) Å for 2b. A key geometrical feature is that the N-Mo-N angle of 72.40 (4)° in CyLMoO2 is slightly less than that of the PhLMoO2 angle of 75.18 (6)°, which is attributed to the flexibility of the cyclo-hexane ring between the nitro-gen as compared to the rigid phenyl ring in the PhLMoO2.