Mono Versus Dinuclear Vanadium(V) Complexes: Solvent Dependent Structural Versatility and Electro Syntheses of Mixed-Valence Oxovanadium(IV/V) Entities in Solution

Two mononuclear oxidovanadium(V) complexes type of [V^VO(L¹)(OMe)(MeOH)] (1), [V^VO(L²)(OMe)(MeOH)] (2) and two [V₂O₃]⁴⁺ core of μ-oxidodioxidodivanadium(V) complexes (L¹)(O)V^V-O-V^V(O)(L¹) (3) and (L²)(O)V^V-O-V^V(O)(L²) (4) and two complexes [V^VO(L¹)(8-Hq)] (5) and [V^VO(L²)(8-Hq)] (6) incorporating 8-hydroxyquinoline (8-hq) as co-ligand have been reported where L¹ [(E)-N'-(2-hydroxybenzylidene)cinnamohydrazide] and L² [(2E,N'E)-N'-(2-hydroxybenzylidene)-3-(naphthalen-1-yl)acrylohydrazide] are the dianionic forms of the conjugated keto-imine functionalized substituted hydrazone ligands. The μ-oxidodioxidodivanadium complexes are generated upon switching the solvent from methanol to acetonitrile. The X-ray analysis showed octahedral geometry for the mononuclear complexes 1, 2 and 5 but oxido-bridged dinuclear complexes 3 and 4 formed penta-coordinated square-pyramidal geometry about metal atoms. Two mixed-valence species of type II, 3a and 4a, of general formulae (L)(O)V^IV-O-V^V(O)(L), are being generated upon constant potential electrolysis (CPE) of 3 and 4 respectively. Frozen solution EPR spectra have 13 hyperfine lines, revealing the unpaired electron is majorly localized on one of the two vanadium centres. All these complexes have been well characterized by physio-chemical techniques and the density functional theory (DFT) calculations were applied to obtain further insight into the electronic structure of this type of molecule. The oxidomethoxido complexes 1 and 2 were taken to investigate the catechol oxidase mimicking activity following the oxidation of 3,5-di-tert-butyl catechol (3,5-DTBC) to 3,5-di-tert-butyl benzoquinone (3,5-DTBQ).

Green synthesis of fluorescent Schiff bases: chemo-photophysical characterization, X-ray structures, and their bioimaging

Two Schiff bases have been prepared by mechano- and ultrasound-assisted synthesis and their structures were elucidated by X-ray diffraction. One of them showed good fluorescent cell staining in vitro and low cytotoxicity.

Preferential intermolecular interactions in a racemic mixture of amino acid Schiff base, conformational structures in solid state, and DFT studies

In this work, we report the green synthesis of a Shiff base [N-(2-hydroxy-1-naphthylidene)-l-phenylalanine (1)] derived from an α-amino acid through an ultrasound-assisted synthesis method with excellent chemical yield in a short period of time.

Chiral arylideneaminoimidazolidin-4-ones: green synthesis and isomerisation mechanism in solution

Arylideneaminoimidazolidin-4-ones synthesized from (l)-α-amino acid via a full green procedure in water (atom economy 91.7% and E-factor 0.09) have been investigated by NMR spectroscopies and DFT calculations, highlighting a development of the species according to an isomerization mechanism.

Green synthesis of new chiral 1-(arylamino)imidazo[2,1-a]isoindole-2,5-diones from the corresponding α-amino acid arylhydrazides in aqueous medium

New chiral 1-(arylamino)imidazo[2,1-a]isoindole-2,5-dione derivatives were obtained in good to excellent yields via the cyclocondensation of 2-formylbenzoic acid and various α-amino acid arylhydrazides using water as the solvent in the presence of sodium dodecyl sulfate as the surfactant and under simple and minimum manipulation, without purification. The reaction is totally diastereoselective and gives access to the nitrogenated tricyclic core with a relative trans stereochemistry.