A new di-μ-oxo bis[oxovanadium(V)] complex containing Schiff base ligand derived from 1,2-diaminopropane and 2′-hydroxy-4′-methoxyacetophenone: Synthesis, structure and catalytic properties

Systematic Development of Vanadium Catalysts for Sustainable Epoxidation of Small Alkenes and Allylic Alcohols

The catalytic epoxidation of small alkenes and allylic alcohols includes a wide range of valuable chemical applications, with many works describing vanadium complexes as suitable catalysts towards sustainable process chemistry. But, given the complexity of these mechanisms, it is not always easy to sort out efficient examples for streamlining sustainable processes and tuning product optimization. In this review, we provide an update on major works of tunable vanadium-catalyzed epoxidations, with a focus on sustainable optimization routes. After presenting the current mechanistic view on vanadium catalysts for small alkenes and allylic alcohols' epoxidation, we argue the key challenges in green process development by highlighting the value of updated kinetic and mechanistic studies, along with essential computational studies.

Crystal structure of (E)-N-cyclo-hexyl-2-(2-hy-droxy-3-methyl-benzyl-idene)hydrazine-1-carbo-thio-amide

The asymmetric unit of the title compound, C15H21N3OS, comprises of two crystallographically independent mol-ecules (A and B). Each mol-ecule consists of a cyclo-hexane ring and a 2-hy-droxy-3-methyl-benzyl-idene ring bridged by a hydrazinecarbo-thio-amine unit. Both mol-ecules exhibit an E configuration with respect to the azomethine C=N bond. There is an intra-molecular O-H⋯N hydrogen bond in each mol-ecule forming an S(6) ring motif. The cyclo-hexane ring in each mol-ecule has a chair conformation. The benzene ring is inclined to the mean plane of the cyclo-hexane ring by 47.75 (9)° in mol-ecule A and 66.99 (9)° in mol-ecule B. The mean plane of the cyclo-hexane ring is inclined to the mean plane of the thio-urea moiety [N-C(=S)-N] by 55.69 (9) and 58.50 (8)° in mol-ecules A and B, respectively. In the crystal, the A and B mol-ecules are linked by N-H⋯S hydrogen bonds, forming 'dimers'. The A mol-ecules are further linked by a C-H⋯π inter-action, hence linking the A-B units to form ribbons propagating along the b-axis direction. The conformation of a number of related cyclo-hexa-nehydrazinecarbo-thio-amides are compared to that of the title compound.

Schiff base-nickel, palladium, and platinum complexes derived from N-cyclohexyl hydrazine carbothioamide and 3-hydroxy-4-methoxybenzaldehyde: Selective antiproliferative and proapoptotic effects against colorectal carcinoma

The bidentate N-cyclohexyl-2-(3-hydroxy-4-methoxybenzylidene)hydrazine-1-carbothioamide Schiff base ligand (HL) was coordinated to divalent nickel, palladium and platinum ions to form square planar complexes. The nickel and palladium complexes, [NiL₂ ], [PdL₂ ] form square planar complexes with 2:1 ligand to metal ratio. The platinum complex, [PtL(dmso)Cl] formed a square planar complex with 1:1 ligand to metal ratio. Platinum undergoes in situ reaction with DMSO before complexing with the ligand in solution. The cytotoxicity of HL, [NiL₂ ], [PdL₂ ], and [PtL(dmso)Cl] were evaluated against human colon cancer cell line (HCT-116), human cervical cancer (Hela) cell line, melanoma (B16F10) cells, and human normal endothelial cell lines (Eahy926) by MTT assay. The [NiL₂ ] complex displayed selective cytotoxic effect against the HCT 116 cancer cell line with IC₅₀ of 7.9 ± 0.2 μM. However, HL, [PdL₂ ], and [PtL(dmso)Cl] only exhibited moderate cytotoxic activity with IC₅₀ = 75.9 ± 2.4, 100.0 ± 1.8, and 101.0 ± 3.6 μM, respectively. The potent cytotoxicity of [NiL₂ ] was characterized using Hoechst and Rhodamine assays. The nickel complex, [NiL₂ ], caused remarkable nuclear condensation and reduction in mitochondrial membrane potential. In addition, molecular docking studies confirms that [NiL₂ ] possesses significant binding efficiency with Tyrosine kinase. Altogether, the results revealed that [NiL₂ ] exhibits cytotoxicity against the cancer cells via Tyrosine kinase-induced proapoptosis pathway. This study demonstrates that the [NiL₂ ] complex could be a promising therapeutic agent against colorectal carcinoma.

Analysis of energies of halogen and hydrogen bonding interactions in the solid state structures of vanadyl Schiff base complexes

Four vanadyl Schiff base complexes have been prepared and characterized. Energies of supramolecular interactions in complexes 1, 2 and 3 were estimated using DFT calculations, and further corroborated with NCI plot index computational tool.

Stabilization of two conformers via intra- or inter-molecular hydrogen bonds in a dinuclear vanadium(v) complex with a pendant Schiff base: theoretical insight

A dinuclear vanadium(v) complex, (μ-O)₂[V(O)(L)]₂, [where HL = 2-methoxy-6-((2-(2-hydroxyethylamino)ethylimino)methyl)phenol] has been synthesized and characterized by spectral and elemental analysis. A single crystal X-ray diffraction study confirms it structure. Two different conformations, stabilized via either intra- or inter-dinuclear hydrogen bonding interactions, co-exist in the solid-state structure. The energies of these intra- or inter-dinuclear hydrogen bonding interactions have been estimated by Density functional theory (DFT) calculations. A ‘Non-covalent interaction’ (NCI) plot has also been used to characterize these interactions.

Two different hydrogen bonded conformers coexist in a synthesized dinuclear oxovanadium(v) Schiff base. Density functional theory (DFT) calculations were utilized to calculate the energies involved in two different conformers.

Crystal structure of (E)-2-[3-(tert-but-yl)-2-hy-droxy-benzyl-idene]-N-cyclo-hexyl-hydrazine-1-carbo-thio-amide

In the title compound, C18H27N3OS, the cyclo-hexane ring has a chair conformation. The azomethine C=N double bond has an E configuration. The nearly planar hydrazinecarbo-thio-amide moiety and substituted benzene ring are twisted by 31.13 (5)° relative to each other. The amide moiety and the cyclo-hexane ring are almost perpendicular to each other; a similar conformation was previously observed in reported structures. In the crystal, mol-ecules are linked by N-H⋯S hydrogen bonds, forming inversion dimers with an R 2 2(8) ring motif.

Influence of the lanthanide(iii) ion in {[Cu3Ln2(oda)6(H2O)6]·nH2O}n (LnIII: La, Gd, Yb) catalysts on the heterogeneous oxidation of olefins

{[Cu₃Ln₂(oda)₆(H₂O)₆]·nH₂O}_n (Ln^III: La, Gd, Yb; odaH₂: oxydiacetic acid) are reported as reusable heterogeneous catalysts in the oxidation of olefins.

Development of a multifunctional biomimicking l-cysteine based oxovanadium(iv) complex: synthesis, DFT calculations, bromo-peroxidation and nuclease activity

An oxovanadium complex [VO(sal-l-cys)(phen)] (sal-l-cys = Schiff base derived from salicylaldehyde and l-cysteine; phen = 1,10-phenanthroline) has been synthesized and characterized by spectroscopic studies (IR, UV-vis, ESI-MS and EPR studies).

Di-μ-oxido-bis-[(2-eth-oxy-6-{[2-(2-hy-droxy-ethyl-amino)-ethyl-imino]-meth-yl}phenolato-κN,N',O)oxidovanadium(V)]

In the title centrosymmetric dinuclear dioxidovanadium(V) complex, [V₂(C₁₃H₁₉N₂O₃)₂O₄], the V^V ion is coordinated by an N,N′,O-tridendate 2-eth­oxy-6-{[2-(2-hy­droxy­ethyl­amino)­ethyl­imino]­meth­yl}phenolate ligand and three oxide O atoms, forming a distorted cis-VN₂O₄ octa­hedral geometry. The bridging O atoms show one short and one long bond to their two attached V^V atoms. The dihedral angle between the benzene ring of the ligand and the V₂O₂ plane is 75.2 (3)°. The deviation of the V^V ion from the plane defined by the three donor atoms of the tridentate ligand and one bridging oxide O atom is 0.337 (2) Å towards the terminal oxide O atom. Two N—H⋯O hydrogen bonds help to establish the conformation of the dimer. In the crystal, the complex mol­ecules are linked by O—H⋯O hydrogen bonds, forming [100] chains.

2-{(1E)-1-[(3-{(E)-[1-(2-Hydroxy-4-methoxyphenyl)ethylidene]amino}-2,2-dimethylpropyl)imino]ethyl}-5-methoxyphenol

Mol­ecules of the title compound, C₂₃H₃₀N₂O₄, are located on a crystallographic mirror plane. The mol­ecule has a curved shape with the dihedral angle formed between the two benzene rings being 55.26 (5)°. Intra­molecular O—H⋯N hydrogen bonds are noted. In the crystal, supra­molecular layers are formed in the ac plane owing to the presence of C—H⋯π inter­actions.

Di-μ-oxido-bis-({(R)-(-)-2-[1-(2-amino-propyl-imino)eth-yl]-1-naphtholato-κN,N',O}oxidovanadium(V))

In the title dinuclear compound, [V₂(C₁₅H₁₇N₂O)₂O₄], each V^V atom is six-coordinated by one oxide group, and by two N and one O atom of the tridentate Schiff base ligand, and bridged by two additional oxide O atoms, resulting in a centrosymmetric dimer. The metal centre has a distorted octa­hedral coordination with the monoanionic Schiff base ligand occupying one equatorial and two axial coordination positions. The separation between V atoms is 3.214 (3) Å. In the crystal structure, there are N—H⋯O, C—H⋯O and C—H⋯π hydrogen bonds, and π–π inter­actions.