Chloromethylated polystyrene cross-linked with divinylbenzene and grafted with vanadium(IV) and vanadium(V) complexes having ONO donor ligand for the catalytic activity

Mononuclear/Binuclear [VIVO]/[VVO2] Complexes Derived from 1,3-Diaminoguanidine and Their Catalytic Application for the Oxidation of Benzoin via Oxygen Atom Transfer

Ligands H₄sal-dag (I) and H₄Brsal-dag (II) derived from 1,3-diaminoguanidine and salicylaldehyde or 5-bromosalicylaldehyde react with one or 2 mol equivalent of vanadium precursor to give two different series of vanadium complexes. Thus, complexes [V^IVO(H₂sal-dag) (H₂O)] (1) and [V^IVO(H₂Brsal-dag) (H₂O)] (2) were isolated by the reaction of an equimolar ratio of these ligands with [V^IVO(acac)₂] in MeOH. In the presence of K⁺/Cs⁺ ion and using aerially oxidized [V^IVO(acac)₂], the above reaction gave complexes [K(H₂O){V^VO₂(H₂sal-dag)}]₂ (3), [Cs(H₂O){V^VO₂(H₂sal-dag)}]₂ (4), [K(H₂O){VO₂(H₂Brsal-dag)}]₂ (5), and [Cs(H₂O){V^VO₂(H₂Brsal-dag)}]₂ (6), which could also be isolated by direct aerial oxidation of complexes 1 and 2 in MeOH in the presence of K⁺/Cs⁺ ion. Complexes [(H₂O)V^IVO(Hsal-dag)V^VO₂] (7) and [(H₂O)V^IVO(HBrsal-dag)V^VO₂] (8) were isolated upon increasing the ligand-to-vanadium precursor molar ratio to 1:2 under an air atmosphere. When I and II were reacted with aerially oxidized [V^IVO(acac)₂] in a 1:2 molar ratio in MeOH in the presence of K⁺/Cs⁺ ion, they formed [K(H₂O)₅{(V^VO₂)₂(Hsal-dag)}]₂ (9), [Cs(H₂O)₂{(V^VO₂)₂(Hsal-dag)}]₂ (10), [K₂(H₂O)₄{(V^VO₂)₂(Brsal-dag)}]₂ (11), and [Cs₂(H₂O)₄{(V^VO₂)₂(Brsal-dag)}]₂ (12). The structures of complexes 3, 4, 5, and 9 determined by single-crystal X-ray diffraction study confirm the mono-, bi-, tri-, and tetra-anionic behaviors of the ligands. All complexes were found to be an effective catalyst for the oxidation of benzoin to benzil via oxygen atom transfer (OAT) between DMSO and benzoin. Under aerobic condition, this oxidation also proceeds effectively in the absence of DMSO. Electron paramagnetic resonance and ⁵¹V NMR studies demonstrated the active role of a stable V(IV) intermediate during OAT between DMSO and benzoin.

Photocatalyzed oxidative cleavage of CC bond to carbonyl compounds by a recyclable homogeneous carbon nitride semiconductor/aqueous system

The development of methods based on direct oxidative cleavage of alkynes to carbonyls is an extremely challenging task. In this work, we describe a UV light-driven, potassium/sodium poly(heptazine imide) (K,Na-PHI)-catalyzed protocol for the selective oxidative cleavage of alkynes to acids under an O₂ atmosphere using water as a solvent. Various aromatic alkynes can be selectively cleaved to afford aromatic acids in good to high yield under clean, mild conditions. Mechanistic investigation indicates that the photogenerated hydroxyl radicals in situ act as green oxidation active species. Moreover, this protocol could be further developed as a sequential oxidative cleavage/esterification process for the preparation of aryl esters. Notably, the KNaPHI-II/water catalyst system could be used several times without significant loss of activity.

An Indole-Based Fluorescent Chemosensor for Detecting Zn2+ in Aqueous Media and Zebrafish

An indole-based fluorescent chemosensor IH-Sal was synthesized to detect Zn²⁺. IH-Sal displayed a marked fluorescence increment with Zn²⁺. The detection limit (0.41 μM) of IH-Sal for Zn²⁺ was greatly below that suggested by the World Health Organization. IH-Sal can quantify Zn²⁺ in real water samples. More significantly, IH-Sal could determine and depict the presence of Zn²⁺ in zebrafish. The detecting mechanism of IH-Sal toward Zn²⁺ was illustrated by fluorescence and UV–visible spectroscopy, DFT calculations, ¹H NMR titration and ESI mass.

C3N4-Photocatalyzed aerobic oxidative cleavage of CC bonds in alkynes with diazonium salts leading to two different aldehydes or esters in one pot

C₃N₄-Photocatalyzed oxidative cleavage of CC bonds in alkynes with diazonium salts to obtain two different aldehydes or esters.

In vitrocytotoxicity and catalytic evaluation of dioxidovanadium(v) complexes in an azohydrazone ligand environment

Synthesis, characterization,in vitrocytotoxicity and catalytic potential of the dioxidovanadium(v) complexes of azohydrazones.

Chemistry of Monomeric and Dinuclear Non-Oxido Vanadium(IV) and Oxidovanadium(V) Aroylazine Complexes: Exploring Solution Behavior

A series of mononuclear non-oxido vanadium(IV) [V(IV)(L(1-4))2] (1-4), oxidoethoxido vanadium(V) [V(V)O(L(1-4))(OEt)] (5-8), and dinuclear μ-oxidodioxidodivanadium(V) [V(V)2O3(L(1))2] (9) complexes with tridentate aroylazine ligands are reported [H2L(1) = 2-furoylazine of 2-hydroxy-1-acetonaphthone, H2L(2) = 2-thiophenoylazine of 2-hydroxy-1-acetonaphthone, H2L(3) = 1-naphthoylazine of 2-hydroxy-1-acetonaphthone, H2L(4) = 3-hydroxy-2-naphthoylazine of 2-hydroxy-1-acetonaphthone]. The complexes are characterized by elemental analysis, by various spectroscopic techniques, and by single-crystal X-ray diffraction (for 2, 3, 5, 6, 8, and 9). The non-oxido V(IV) complexes (1-4) are quite stable in open air as well as in solution, and DFT calculations allow predicting EPR and UV-vis spectra and the electronic structure. The solution behavior of the [V(V)O(L(1-4))(OEt)] compounds (5-8) is studied confirming the formation of at least two different types of V(V) species in solution, monomeric corresponding to 5-8, and μ-oxidodioxidodivanadium [V(V)2O3(L(1-4))2] compounds. The μ-oxidodioxidodivanadium compound [V(V)2O3(L(1))2] (9), generated from the corresponding mononuclear complex [V(V)O(L(1))(OEt)] (5), is characterized in solution and in the solid state. The single-crystal X-ray diffraction analyses of the non-oxido vanadium(IV) compounds (2 and 3) show a N2O4 binding set and a trigonal prismatic geometry, and those of the V(V)O complexes 5, 6, and 8 and the μ-oxidodioxidodivanadium(V) (9) reveal that the metal center is in a distorted square pyramidal geometry with O4N binding sets. For the μ-oxidodioxidodivanadium species in equilibrium with 5-8 in CH2Cl2, no mixed-valence complexes are detected by chronocoulometric and EPR studies. However, upon progressive transfer of two electrons, two distinct monomeric V(IV)O species are detected and characterized by EPR spectroscopy and DFT calculations.

Vanadium(iv and v) complexes of pyrazolone based ligands: Synthesis, structural characterization and catalytic applications

Four different types of novel vanadium(iv and v) complexes have been isolated and characterized. Complexes [V^VO(OMe)(L)] are used as catalysts in the oxidative aromatization of Hantzsch 1,4-dihydropyridine derivatives and in the oxidation of tetralin.

A family of mixed-ligand oxidovanadium(v) complexes with aroylhydrazone ligands: a combined experimental and computational study on the electronic effects of para substituents of hydrazone ligands on the electronic properties, DNA binding and nuclease activities

Substituents at 5-position in the acetophenone ring of the hydrazone ligands in a family of mixed-ligand oxidovanadium(v) complexes show marked influence on the electronic properties, DNA binding ability and nuclease activity.