Antiplatelet properties of novel N-substituted-phenyl-1,2,3-triazole-4-acylhydrazone derivatives

Efficient synthesis of 3-alkyl-2-(-1H-1,2,3-triazolyl)methyl)thio)-2,3-dihydroquinazolin-4(1H)-one derivative via multistep synthesis approach by novel Cu@Py-Oxa@SPION catalyst

In this pared, an efficient method is introduced for the synthesis of 3-alkyl-2-(((4-(2-oxopropyl)-1H-1,2,3-triazol-1-yl)alkyl)thio)-2,3-dihydroquinazolin-4(1H)-one derivatives. These novel products have both 1,2,3-triazole and quinazolinone in their structures. For the synthesis of these products, a novel catalyst is designed, synthesized, and characterized by the immobilization of copper onto modified magnetic iron oxide. The catalyst (denoted: Cu@Py-Oxa@SPION) was characterized by several characterization techniques. In this regard, 16 3-alkyl-2-(((4-(2-oxopropyl)-1H-1,2,3-triazol-1-yl)alkyl)thio)-2,3-dihydroquinazolin-4(1H)-one derivatives were synthesized in high isolated yields (77-86%). As an advantage, the catalyst is highly recoverable and its activity has not decreased after 7 sequential runs. The method is very efficient for the synthesis of the products in high isolated yields under mild reaction conditions in a green solvent. The scope of the method is broad and several examples were successfully synthesized using starting materials with different functional groups.

Structure-Activity Relationship Analysis of Rhosin, a RhoA GTPase Inhibitor, Reveals a New Class of Antiplatelet Agents

Current antiplatelet therapies have several clinical complications and are mostly irreversible in terms of suppressing platelet activity; hence, there is a need to develop improved therapeutic agents. Previous studies have implicated RhoA in platelet activation. Here, we further characterized the lead RhoA inhibitor, Rhosin/G04, in platelet function and present structure-activity relationship (SAR) analysis. A screening for Rhosin/G04 analogs in our chemical library by similarity and substructure searches revealed compounds that showed enhanced antiplatelet activity and suppressed RhoA activity and signaling. A screening for Rhosin/G04 analogs in our chemical library using similarity and substructure searches revealed compounds that showed enhanced antiplatelet activity and suppressed RhoA activity and signaling. SAR analysis revealed that the active compounds have a quinoline group optimally attached to the hydrazine at the 4-position and halogen substituents at the 7- or 8-position. Having indole, methylphenyl, or dichloro-phenyl substituents led to better potency. Rhosin/G04 contains a pair of enantiomers, and S-G04 is significantly more potent than R-G04 in inhibiting RhoA activation and platelet aggregation. Furthermore, the inhibitory effect is reversible, and S-G04 is capable of inhibiting diverse-agonist-stimulated platelet activation. This study identified a new generation of small-molecule RhoA inhibitors, including an enantiomer capable of broadly and reversibly modulating platelet activity.

Synthesis, structural characterization, and evaluation of new peptidomimetic Schiff bases as potential antithrombotic agents

New Schiff bases functionalized with amide and phenolic groups synthesized by the condensation of 2-hydroxybenzaldehyde and 2-hydroxyacetophenone with amino acid amides which in turn were prepared in two steps from N-Boc-amino acids and homoveraltrylamine through intermediate compounds N-Boc-amino acids amides. The compounds were characterized by elemental analysis, FT-IR, UV–Vis, and NMR spectroscopy. The crystal structures of three Schiff bases were determined by single crystal X-ray diffraction. There exists O–H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\cdots $$\end{document}⋯N, N–H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\cdots $$\end{document}⋯O, and C–H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\cdots $$\end{document}⋯O types of hydrogen bonds and C–H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\cdots\uppi $$\end{document}⋯π secondary bonding interactions in these crystalline solids. The Schiff bases have been screened for anticoagulant and antiplatelet aggregation activities. All the compounds showed procoagulant activity which shortens the clotting time of citrated human plasma in both platelet-rich plasma and platelet-poor plasma except the derivatives of L-methionine which showed anticoagulant activity by prolonging the clotting time. In addition, the compounds derived from benzyl cysteine and phenylalanine showed adenosine diphosphate induced antiplatelet aggregation activity, whereas others did not show any role. Moreover, all these compounds revealed non-hemolytic activity with red blood cells.

Molecular docking studies on COVID-19 and antibacterial evaluation of newly synthesized 4-(methoxymethyl)-1,2,3-triazolean analogues derived from (E)-1-phenyl-3-(2-(piperidin-1-yl)quinolin-3-yl) prop-2-en-1-one

A series of novel quinolone-based 4-(methoxymethyl)-1,2,3-triazole derivatives were synthesized, and their structures were characterized by ¹H, ¹³C NMR and mass spectroscopy. The compounds (IXa-l) were screened in vitro antibacterial activity against five gram-positive and five gram-negative bacterial strains, viz. M. Tuberculosis, M. Luteus, MRSA, B. Subtilis, B. Cereus, P. Aerginosa, K. Pneumonia, E. Coli, P. Vulgaris and S. Typhi, used and compared with standard gentamycin. The combination of the pharmacologically active moieties in a single scaffold results in their synergistic effect and high antimicrobial activity against several bacterial strains. COVID-19 has spread rapidly around the globe since its first identification in Wuhan, China, in December 2019. Coronavirus Disease 2019 (COVID‐19 Mpro) has become a major health problem causing severe acute respiratory illness in humans. The causative virus is called severe acute respiratory syndrome coronavirus 2, and the World Health Organization named the new epidemic disease Coronavirus Disease (COVID-19). Also, docking studies demonstrated that all derivatives exhibit a good theoretical affinity with Autodock 4.2 software score in between − 9.89 and − 13.4 kCal/mol against the main protease of COVID‐19 Mpro that caused worldwide epidemics. We believe that newly synthesized quinolone-based 4-(methoxymethyl)-1,2,3-triazole derivatives can guide many future studies in organic synthesis, medicine and pharmaceutical applications.

Bioactive 1,2,3-Triazoles: An Account on their Synthesis, Structural Diversity and Biological Applications

The triazole heterocycle is a privileged scaffold in medicinal chemistry, since its structure is present in a large number of biologically active molecules, including several drugs currently in the market. Due to their vast applications, a wide variety of methods are described for their preparation, such as the 1,3-dipolar cycloaddition and processes involving diazo compounds and diazo transfer reactions. Considering the significant number of contributions from our research group to this chemistry in recent decades, in this account we discuss both the development of new methods for the synthesis of 1,2,3-triazoles and the preparation of new triazole-functionalized biologically active molecules using classical approaches.

Synthesis, Molecular Docking Studies and Biological Evaluation of N-Acylarylhydrazones as Anti-Inflammatory Agents

In the present work a series of N'-arylidene-2-(benzamido)-3-(naphthalen-2-yl)acrylohydrazides were synthesized by refluxing the intermediate 2-(benzamido)-3-(naphthalen-2-yl)acrylohydrazide with various substituted benzaldehyde in the presence of glacial acetic acid. The intermediate 2-(benzamido)-3-(naphthalen-2-yl)acrylohydrazide 2 was prepared by stirring 4-((naphthalen-2-yl)methylene)-2-phenyloxazol-5(4H)-one with hydrazine hydrate in the presence of absolute ethanol. The chemical structures of the compounds were established by IR, ¹H NMR and mass spectral data. All the compounds were evaluated for anti-inflammatory (in vivo, in vitro) activity and performed docking against COX-2. The compounds 3a, 3c and 3o showed good inhibition of COX-2 in in vitro studies (0.75 μM, 0.5 μM and 0.7 μM as IC50, respectively). The compounds 3c, 3e and 3f were found to be more active than standard drug phenylbutazone at equidose. Molecular docking studies showed that compound 3 m exhibited good binding affinity against COX-2 with docking score 9.328 kcal/mol, when compared to the standard celecoxib.

Synthesis of 4-Methoxy-1, 3-Benzenediolylhydrazones and Evaluation of Their Anti-Platelet Aggregation Activity

In our present investigation, a series of novel 4-methoxy-1,3-benzenediolyl-hydrazones were designed and synthesized, and their ability to inhibit platelet aggregation was evaluated by adenosine diphosphate (ADP) and arachidonic acid (AA). The structures of the synthesized compounds were confirmed by spectral data. Results demonstrated that the activities of all compounds excelled the positive drug Picotamide (25.1% inhibition rate) and seven compounds (PNN01, PNN03, PNN05, PNN07, PNN09, PNN12, and PNN14) have efficiently inhibited platelet aggregation even higher than Clopidogrel (37.6% inhibition rate) induced by AA. Among them, PNN07 (39.8% inhibition rate) was considered as the most potent analogue. Evaluation of cytotoxic activity of the compounds against L929 cell line revealed that none of the compounds have significant cytotoxicity. Thus, diolylhydrazones derives are potential to be antiplatelet aggregation inhibitors and maybe working in AA-induced selectively.

Simultaneous formation of non-oxidovanadium(iv) and oxidovanadium(v) complexes incorporating phenol-based hydrazone ligands in aerobic conditions

A family of non-oxidovanadium(iv) complexes incorporating multidentate hydrazone ligands were synthesized through a thermodynamically unfavourable process along with oxidovanadium(v) species.

A Series of New Hydrazone Derivatives: Synthesis, Molecular Docking and Anticholinesterase Activity Studies

BACKGROUND

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are known to be serine hydrolase enzymes responsible for the hydrolysis of acetylcholine (ACh), which is a significant neurotransmitter for regulation of cognition in animals. Inhibition of cholinesterases is an effective method to curb Alzheimer's disease, a progressive and fatal neurological disorder.

OBJECTIVE

In this study, 30 new hydrazone derivatives were synthesized. Then we evaluated their anticholinesterase activity of compounds. We also tried to get insights into binding interactions of the synthesized compounds in the active site of both enzymes by using molecular docking approach.

METHODS

The compounds were synthesized by the reaction of various substituted/nonsubstituted benzaldehydes with 6-(substitute/nonsubstituephenyl)-3(2H)-pyridazinone-2-yl propiyohydrazide. Anticholinesterase activity of the compounds was determined using Ellman's method. Molecular docking studies were done by using the ADT package version 1.5.6rc3 and showed by Maestro. RMSD values were obtained using Lamarckian Genetic Algorithm and scoring function of AutoDock 4.2 release 4.2.5.1 software.

RESULTS

The activities of the compounds were compared with galantamine as cholinesterase enzyme inhibitor, where some of the compounds showed higher BChE inhibitory activity than galantamine. Compound F111 was shown to be the best BChE inhibitor effective in 50 μM dose, providing 89.43% inhibition of BChE (IC50=4.27±0.36 μM).

CONCLUSION

This study supports that novel hydrazone derivates may be used for the development of new BChE inhibitory agents.

Arylhydrazone ligands as Cu-protectors and -catalysis promoters in the azide-alkyne cycloaddition reaction

A series of water soluble copper(ii) complexes, [Cu(κO¹O²N-H₂L¹)(H₂O)₂]·2H₂O (2), [Cu(κO-H₃L¹)₂(H₂O)₄] (3), [Cu(κO-H₄L²)₂(H₂O)₄] (5) and [Cu(H₂O)₆]·2H₂L³·2(CH₃)₂NCHO (7), were prepared by the reaction of Cu(NO₃)₂·3H₂O with sodium (Z)-2-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)benzenesulfonate, [Na(μ₄-1:2κO¹,2κO²,3κO³,4κO⁴-H₃L¹)]_n (1; for 2 and 3), sodium (Z)-3-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)-4-hydroxybenzene-sulfonate, [Na(μ-1κO¹,2κO²-H₄L²)]₂ (4; for 5) or sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazineyl)naphthalene-1-sulfonate, [Na(μ-1κO¹O²,2κO³-H₂L³)(CH₃OH)₂]₂ (6; for 7). Compounds 1-7 were fully characterized, also by single-crystal X-ray diffraction analysis, and applied as homogeneous catalysts for the azide-alkyne cycloaddition (AAC) reaction to afford 1,4-disubstituted 1,2,3-triazoles. A structure-catalytic activity relationship has been recognized for the first time on the basis of the occurrence of resonance- and charge-assisted hydrogen bond interactions (RAHB and CAHB), in charge and ligand binding modes, enabling the catalytic activity of the compounds to be ordered as follows: Cu(NO₃)₂≪7 (complex salt with RAHB and CAHB) < 3 (with RAHB and CAHB) < 5 (with RAHB) < 2 (neither RAHB nor CAHB). Complex 2, without such non-covalent interactions, was found to be the most efficient catalyst for the AAC reaction, affording up to 98% product yield after being placed for 15 min, at 125 °C, in a water/acetonitrile mixture under low power (10 W) MW irradiation.

Synthesis, characterization, and cytotoxic and antimicrobial activities of mixed-ligand hydrazone complexes of variable valence VOz+ (z = 2, 3)

Mixed-ligand complexes of VO²⁺ and VO³⁺ motifs incorporating a family of hydrazone ligands were reported, which exhibited promising cytotoxic activity against lung cancer cell line and antimicrobial activity against four pathogenic bacterial stains.

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.

Exploring the effect of substituent in the hydrazone ligand of a family of μ-oxidodivanadium(v) hydrazone complexes on structure, DNA binding and anticancer activity

The reaction of 2-hydroxybenzoylhydrazine (H₂bh) separately with equimolar amounts of [V^IVO(aa)₂] and [V^IVO(ba)₂] in CHCl₃ afforded the complexes [VO₃(HL¹)₂] (1) and [VO₃(HL²)₂] (2) respectively in good to excellent yield ((HL¹)^2- and (HL²)^2- represent respectively the dianionic form of 2-hydroxybenzoylhydrazones of acetylacetone (H₃L¹) and benzoylacetone (H₃L²) (general abbreviation H₃L)). From X-ray structure analysis, the V^V-O-V^V angle was found to be ∼115° and 180° in 1 and 2 respectively. Upon one-electron reduction selectively at one V centre at an appropriate potential, each of 1 and 2 generated mixed-valence [(HL)V^VO-(μ-O)-OV^IV(HL)]^- species 1A and 2A respectively, which showed valence delocalization at room temperature and localization at 77 K, and the V^IV-O-V^V bond angles were calculated to be 177.5° and 180° respectively. The intercalative mode of binding of the two complexes 1 and 2 with CT DNA has been suggested by UV-visible spectroscopy (K_b = 7.31 × 10⁵ M^-1 and 8.71 × 10⁵ M^-1 respectively for 1 and 2), fluorescence spectroscopy (K_sv = 6.85 × 10⁵ M^-1 and 8.53 × 10⁵ M^-1 respectively for 1 and 2) and circular dichroism spectroscopy. Such intercalative mode of binding of these two complexes with CT DNA and HPV DNA has also been confirmed by molecular docking study. Both complexes 1 and 2 exhibited promising anti-cancer activity against SiHa cervical cancer cells with IC₅₀ values of 28 ± 0.5 μM and 25 ± 0.5 μM respectively for 24 h which is significantly better than that of widely used cisplatin (with IC₅₀ value of 63.5 μM). Nuclear staining experiments reveal that these complexes kill the SiHa cells through apoptotic mode. It is interesting to note that these two complexes are non-toxic to normal T293 cell line. Complex 2 showed higher DNA binding ability with CT DNA and HPV DNA as well as better anti-cancer properties towards SiHa cervical cancer cells in comparison to complex 1, a fact which can be explained by considering the lower energy of LUMO (which favours electron transition from DNA to the metal complex) and also the higher surface area of complex 2 in comparison to complex 1 due to the presence of one extra electron-withdrawing phenyl group in the former.

Hetero-Diels-Alder reactions of novel 3-triazolyl-nitrosoalkenes as an approach to functionalized 1,2,3-triazoles with antibacterial profile

The generation and reactivity of 3-triazolyl-nitrosoalkenes are reported for the first time. The study showed that hetero-Diels-Alder reaction of these heterodienes is an interesting synthetic strategy to functionalized 1,2,3-triazoles, including 1,2,3-triazolyl-pyrroles, 1,2,3-triazolyl-dipyrromethanes and 1,2,3-triazolyl-indoles. The evaluation of the antibacterial profile against Gram-positive and Gram-negative strains revealed the new 5,5'-diethyldipyrromethane bearing a side chain incorporating a triazole and oxime moieties. The antibacterial profile detected was within the Clinical and Laboratory Standard Institute (CLSI) range and against important Staphylococcus species including Methicillin-resistant strain (S. aureus ATCC 25923, S. epidermidis ATCC 12228 and S. simulans ATCC 27851 and MRSA). Interestingly, this new 1,2,3-triazole presented hemocompatibility and low in silico toxicity profile similar to antibiotics current in use. It also has an usual antibiofilm activity against MRSA, which reinforced its potential as a new antibacterial prototype.

Exploring the effect of hydroxylic and non-hydroxylic solvents on the reaction of [VIVO(β-diketonate)2] with 2-aminobenzoylhydrazide in aerobic and anaerobic conditions

Refluxing [V^IVO(β-diketonate)₂], namely [V^IVO(acetylacetonate)₂] and [V^IVO(benzoylacetonate)₂], separately with an equivalent or excess amount of 2-aminobenzoylhydrazide (ah) in laboratory grade (LG) CH₃OH in aerobic conditions afforded non-oxidovanadium(iv) and oxidovanadium(v) complexes of the type [V^IV(L¹)₂] (1), [V^VO(L¹)(OCH₃)]₂ (3) and [V^IV(L²)₂] (2), and [V^VO(L²)(OCH₃)] (4), respectively. (L¹)^2- and (L²)^2- represent the dianionic forms of 2-aminobenzoylhydrazone of acetylacetone (H₂L¹) and benzoylacetone (H₂L²), respectively, (general abbreviation, H₂L), which was formed by the in situ condensation of ah with the respective coordinated [β-diketonate] in medium-to-good yield. The yield of different resulting products was dependent upon the ratio of ah to [V^IVO(β-diketonate)₂]. For example, the yield of 1 and 2 complexes increased significantly associated with a decrease in the amount of 3 and 4 with an increase in the molar ratio of ah. Upon replacing CH₃OH by a non-hydroxylic solvent, LG CHCl₃, the above reaction yielded only oxidovanadium(v) complexes of the type [V^VO(L¹)(OH)]₂ (5), [V^VO(L²)(OH)] (6) and [VO₃(L)₂] (7, 8) whereas, upon replacing CHCl₃ by another non-hydroxylic solvent, namely LG CH₃CN, only the respective [VO₃(L)₂] (7, 8) complex was isolated in 72-78% yield. However, upon performing the above reactions in the absence of air using dry CH₃OH or dry CHCl₃, only the respective [V^IV(L)₂] complex was obtained, suggesting that aerial oxygen was the oxidising agent and the type of pentavalent product formed was dependent upon the nature of solvent used. Complexes 3 and 4 were converted, respectively, to 7 and 8 on refluxing in LG CHCl₃via the respective unstable complex 5 and 6. The DFT calculated change in internal energy (ΔE) for the reactions 2[V^VO(L²)(OCH₃)] + 2H₂O → 2[V^VO(L²)(OH)] + 2CH₃OH and 2[V^VO(L²)(OH)] → [VO₃(L²)₂] + H₂O was, respectively, +3.61 and -7.42 kcal mol^-1, suggesting that the [V^VO(L²)(OH)] species was unstable and readily transformed to the stable [VO₃(L²)₂] complex. Upon one-electron reduction at an appropriate potential, each of 7 and 8 generated mixed-valence [(L)V^VO-(μ-O)-OV^IV(L)]^- species, which showed valence-delocalisation at room temperature and localisation at 77 K. Some of the complexes showed a wide range of toxicity in a dose-dependent manner against lung cancer cells comparable with that observed with cis-platin.

Synthesis and mechanistic evaluation of novel N'-benzylidene-carbohydrazide-1H-pyrazolo[3,4-b]pyridine derivatives as non-anionic antiplatelet agents

Cardiovascular diseases (CVDs) account for over 17 million deaths globally each year, with atherosclerosis as the underlying cause of most CVDs. Herein we describe the synthesis and in vitro mechanistic evaluation of novel N'-benzylidene-carbohydrazide-1H-pyrazolo[3,4-b]pyridines (3-22) designed as non-anionic antiplatelet agents and presenting a 30-fold increase in potency compared to aspirin. The mechanism underlying their antiplatelet activity was elucidated by eliminating potential targets through a series of in vitro assays including light transmission aggregometry, clot retraction, and quantitative ELISA, further identifying the reduction in biosynthesis of thromboxane B2 as their main mechanism of action. The intrinsic fluorescence of the compounds permits their binding to platelet membranes to be readily monitored. In silico structure-activity relationship, molecular docking and dynamics studies support the biological profile of the series revealing the molecular basis of their activity and their potential as future molecular therapeutic agents.

Design, synthesis, molecular-docking and antimycobacterial evaluation of some novel 1,2,3-triazolyl xanthenones

As part of an ongoing effort to develop new antitubercular and antimicrobial agents, a series of substituted xanthenone derivatives (7a-p) were synthesized. Xanthenone derivatives (7a-p) were prepared via a one-pot three-component thermal cyclization reaction of β-naphthol (5), substituted 1-aryl-1H-[1,2,3]triazole-4-carbaldehydes (4a-h), and cyclic-1,3-diones (6a, b) in the presence of a catalytic amount of iodine. The newly synthesized compounds were characterized by IR, NMR, mass spectral data, and elemental analysis. These compounds (4a-h and 7a-p) were screened for in vitro antitubercular activity against the M. tuberculosis H37Rv (ATCC 27294) strain, for antibacterial activity against Gram-positive and Gram-negative strains, and for antifungal activity against a pathogenic strain of fungi. Among the compounds tested, most of them showed good to excellent antimicrobial and antitubercular activity. The active compounds displaying good potency in the MTB were further examined for toxicity in a HEK cell line. In addition, the structure and antitubercular activity relationship were further supported by in silico molecular-docking studies of the active compounds against the pantothenate synthetase (PS) enzyme of M. tuberculosis.

Regiospecific Synthesis of 1,4,5-Trisubstituted 1,2,3-Triazoles via Enolate–Azide Cycloaddition between 1,3-Dicarbonyl Compounds and Aryl Azides

A cycloaddition reaction at room temperature between aryl azides and 1,3-dicarbonyl compounds in the presence of potassium carbonate in dimethylsulphoxide yielded 10 4-ethoxycarbonyl-1-aryl-5-methyl-1 H-1,2,3-triazoles and seven other closely-related compounds. The 1,2,3-triazoles, nine of which are new, were obtained in good to high yields and only the 1,4-regioisomers were formed.

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.