1H-NMR study on the tautomer ratios between the hydrazone imine and diazenylenamine forms in 3-(arylhydrazono)-methyl-2-oxo-1,2-dihydroquinoxalines

The o-substituted 3-(arylhydrazono)methyl-2-oxo-1,2-dihydroquinoxalines 1a-c and 2a , c were synthesized to investigate the tautomeric behavior between the hydrazone imine A and diazenylenamine B forms in a series of mixed dimethyl sulfoxide/trifluoroacetic acid media. The chemical shifts of the hydrazone NH, N₄-H, hydrazone CH, and diazenyl CH protons for o-, m-, and p-substituted 3-(arylhydrazono)methyl-2-oxo-1,2-dihydroquinoxalines 1 and 2 synthesized so far are summarized in Tables 3 and 4, respectively, which are found to be useful for the specification of the proton signals due to the hydrazone imine form A (hydrazone NH, hydrazone CH) and diazenylenamine form B (N₄-H, diazenyl CH).     

Synthesis and crystal structures of N′-(3-ethoxy-2-hydroxybenzylidene)-3-methylbenzohydrazide and its dioxomolybdenum(VI) complex

A new hydrazone N′-(3-ethoxy-2-hydroxybenzylidene)-3-methylbenzohydrazide (H₂L), derived from condensation of 3-ethoxysalicylaldehyde with 3-methylbenzohydrazide, and its dioxomolybdenum(VI) complex [MoO₂L(CH₃OH)], have been prepared and characterized by physico-chemical methods and single crystal X-ray diffraction. The hydrazone coordinates to Mo through the phenolate O, imine N, and enolic O. The Mo is six-coordinate in a distorted octahedral geometry, with the three donors of L and one oxo defining the equatorial plane, and with one methanol and another oxo occupying the axial positions. The bond values especially for those related to the donors in the complex are different from those in H₂L.     

New hydroxylated metabolites of 4-monochlorobiphenyl in whole poplar plants

Background

The importance of the isatinic quinolyl hydrazones arises from incorporating the quinoline ring with the indole ring. Quinoline ring has therapeutic and biological activities whereas, the indole ring occurs in Jasmine flowers and Orange blossoms. As a ligand, the isatin moiety is potentially ambidentate and can coordinate the metal ions either through its lactam or lactim forms. In a previous study, the ligational behavior of a phenolic quinolyl hydrazone towards copper(II)- ions has been studied. As continuation of our interest, the present study is planned to check the ligational behavior of an isatinic quinolyl hydrazone.

Results

New homo- and heteroleptic copper(II)- complexes were obtained from the reaction of an isatinic quinolyl hydrazone (HL) with several copper(II)- salts viz. Clˉ, Brˉ, NO₃ˉ, ClO₄ ^-, SO₄ ^2- and AcO^-. The obtained complexes have O_h, T_d and D_4h- symmetry and fulfill the strong coordinating ability of Clˉ, Brˉ, NO₃ˉ and SO₄ ^2- anions. Depending on the type of the anion, the ligand coordinates the copper(II)- ions either through its lactam (NO₃ˉ and ClO₄ ^-) or lactim (the others) forms.

Conclusion

The effect of anion for the same metal ion is obvious from either the geometry of the isolated complexes (O_h, T_d and D_4h) or the various modes of bonding. Also, the obtained complexes fulfill the strong coordinating ability of Clˉ, Brˉ, NO₃ˉ and SO₄ ^2- anions in consistency with the donor ability of the anions. In case of copper(II)- acetate, a unique homoleptic complex (5) was obtained in which the AcO^- anion acts as a base enough to quantitatively deprotonate the hydrazone. The isatinic hydrazone uses its lactim form in most complexes.     

Transition metal complexes of novel tridentate S,N,O donor ligands

Summary Complexes of chromium(III), iron(III), cobalt(III), nickel(II) and copper(II) with salicylaldehyde N(1-piperidyl) thiocarbonyl hydrazone (spthH₂), salicylaldehyde N-(1-morpholyl) thiocarbonyl hydrazone (smthH₂), 2-hydroxy 4-methyl acetophenone N-(1-piperidyl) thiocarbonyl hydrazone (apthH₂) and 2-hydroxy 4-methyl acetophenone N-(1-morpholyl) thiocarbonyl hydrazone (amthH₂) have been prepared and characterized by analytical, spectral and magnetic measurements. Mixed ligand complexes of Cu^II-thiocarbonyl hydrazones and heterocyclic bases have been isolated. Depending on the nature of the metal salts used and the reaction conditions the thiocarbonyl hydrazones act as neutral or dibasic tridentate ligands.     

Crystal structures of new 4-hydroxy-<Emphasis Type="Italic">N</Emphasis>′-(3,5-diiodo-2-hydroxybenzylidene)benzohydrazide methanol and 4-hydroxy-<Emphasis Type="Italic">N</Emphasis>′-(2-methoxynaphth-1-yl-methylene)benzohydrazide dimethanol solvate

Two new hydrazone compounds C₁₄H₁₀I₂N₂O₃·CH₃OH (1) and C₁₉H₁₆N₂O₃·2CH₃OH (2) are synthesized by the condensation reactions of the equimolar quantities of 4-hydroxybenzohydrazide with 3,5-diiodo-2-hydroxybenzaldehyde and 2-methoxynaphth-1-yl-methylene respectively in methanol solutions. Compound 1 consists of a hydrazone molecule and a methanol molecule of crystallization, and compound 2 consists of a hydrazone molecule and two methanol molecules of crystallization. Both compounds are characterized by elemental analysis, IR spectra, and single crystal X-ray diffraction. As expected, each hydrazone molecule adopts an E configuration about the C=N double bond. In the crystal structures of both compounds, the hydrazone and methanol molecules are linked through intermolecular N-H...O and O-H...O hydrogen bonds, forming layers along the bc direction.     

Synthesis,characterization and crystal structures of oxidovanadium(V) hydrazone complexes with antibacterial activity

Abstract

Reaction of VO(acac)₂ with the hydrazone ligands N’-(2-hydroxybenzylidene)-3methylbenzohydrazide (H₂L¹) and N’-(2-hydroxybenzylidene)-3-methyl-4-nitrobenzohydrazide (H₂L²) afforded two oxidovanadium(V) complexes, [VOL¹(OMe)(MeOH)] (1) and [VOL²(OEt)(EtOH)] (2), respectively. The complexes have been characterized by elemental analyses, IR, UV-Vis, molar conductivity and X-ray single crystal diffraction techniques. The hydrazone ligands coordinate to the V ions through the phenolate oxygen, imino nitrogen and enolate oxygen atoms. The V ions in both complexes are in octahedral coordination, with the three donor atoms of the hydrazone ligands, and with the other three sites furnished by one methanol or ethanol oxygen atom, one deprotonated methanol or ethanol oxygen atom, and one oxo oxygen. The complexes were assayed for their antibacterial activity on the bacteria B. subtilis, E. coli, P. putida and S. aureus.     

Synthesis,characterization and crystal structures of cyclometallated Ru(II) carbonyl complexes formed by hydrazones

Cyclometallated Ru(II) complexes of the type [Ru(CO)(EPh₃)₂(L)] (E = P or As; L = tridentate hydrazone-derived ligand) have been obtained by refluxing an ethanolic solution of [RuHCl(CO)(PPh₃)₃] or [RuHCl(CO)(AsPh₃)₃] with the hydrazone derivatives H₂php (2-[(2,4-dinitro-phenyl)-hydrazonomethyl]-phenol), H₂phm (2-[(2,4-dinitro-phenyl)-hydrazonomethyl]-6-methoxy-phenol) and H₂phn (2-[(2,4-dinitro-phenyl)-hydrazonomethyl]-naphthalen-1-ol). The formation of stable cyclometallated complexes has been authenticated by single crystal X-ray structure determination of two of the complexes, and the mechanism of C–H activation is discussed in detail. The spectral (IR, UV–Vis and ¹H NMR) and electrochemical data for all the complexes are reported. Electrochemistry shows a substantial variation in the metal redox potentials with regard to the electronic nature of the substituents present in the hydrazone derivative.     

Two mononuclear molybdenum(VI) oxo complexes with tridentate hydrazone ligands: Synthesis and crystal structures

Reaction of [MoO₂(Acac)₂] (Acac = acetylacetonate) with two similar hydrazone ligands in methanol yielded two mononuclear molybdenum(VI) oxocomplexes with general formula [MoO₂(L)(CH₃OH)], where L = L¹ = (4-nitrophenoxy)acetic acid [1-(3-ethoxy-2-hydroxyphenyl)methylidene]hydrazide (H₂L¹) and L = L² = (4-nitrophenoxy)acetic acid [1-(5-bromo-2-hydroxyphenyl)methylidene]hydrazide (H₂L²). Crystal and molecular structures of the complexes were determined by single crystal X-ray diffraction method. All investigated compounds were further characterized by elemental analysis and FT-IR spectra. Single crystal X-ray structural studies indicate that the hydrazone ligands coordinate to the MoO₂ cores through enolate oxygen, phenolate oxygen, and azomethine nitrogen. The Mo atoms in both complexes are in octahedral coordination.     

Synthesis,spectral characterization and crystal structure studies of a new hydrazone Schiff base and its dioxomolybdenum(VI) complex

A new hydrazone Schiff base, (E)-N′-(3-ethoxy-2-hydroxybenzylidene)isonicotinohydrazide (H₂L), has been prepared and characterized by elemental analyses, spectroscopic methods, and single-crystal X-ray diffraction. The corresponding dioxomolybdenum(VI) complex [Mo(O)₂(L)(CH₃OH)] was synthesized and characterized by spectroscopic methods and by single-crystal X-ray diffraction. The hydrazone ligand coordinates to Mo through the phenolate O, imine N, and enolic O. The Mo center displays a distorted octahedral geometry with the three donors of the ligands and an oxo defining the equatorial plane, and one methanol and another oxo occupying the axial positions.     

Coumarin-naphthohydrazone ligand with a rare coordination mode to form Mn(II) and Co(II) 1-D coordination polymers: synthesis,characterization, and crystal structure

The hydrazone (E)-3-hydroxy-N’-(1-(2-oxo-2H-chromen-3-yl)ethylidene)-2-naphthohydrazide (H₂L) was synthesized from the reaction of 3-acetylcoumarin and 3-hydroxy-2-naphthoic hydrazide in methanol. Compounds [Mn(H₂L)(NO₃)₂(CH₃OH)]·CH₃OH (1a), [Mn(HL)(NO₃)(CH₃OH)]_n (1b), [Co(HL)(NO₃)(CH₃OH)]_n (2), and [Cu(HL)(NO₃)] (3) were obtained by reaction of an equimolar amount of H₂L with nitrate salts of Mn(II), Co(II), or Cu(II) in methanol. The reaction of ligand and Mn(NO₃)₂·4H₂O was also carried out in the presence of sodium azide which led to the 1-D coordination polymer, [Mn(HL)(N₃)(CH₃OH)]_n (4). All of the synthesized compounds were characterized by elemental analyses and spectroscopic methods. Single-crystal X-ray analysis of 1–4 indicated that H₂L is neutral (in 1a) or mononegative ligand (in 1b, 2, 3 and 4). In 1b, 2 and 4 the 1-D polymeric chain is found by a rare coordination mode of this kind of hydrazone ligand since the naphtholic oxygen is coordinated to the neighboring metal ions while the NH moiety of hydrazone remains intact, also confirmed by FT-IR spectroscopic studies. The thermal stability of 2 and 4 were also studied from 30–1000 °C.     

Synthesis,crystal structures and catalytic epoxidation properties of dioxomolybdenum(VI) complexes with hydrazone ligands

A series of dioxomolybdenum(VI) complexes with similar hydrazone ligands have been prepared, specifically [MoO₂L¹(MeOH)] (1), [MoO₂L²(MeOH)] (2) and [MoO₂L³(MeOH)] (3), where L¹, L² and L³ are the dianionic forms of 2-chloro-N′-(2-hydroxybenzylidene)benzohydrazide, 2-chloro-N′-(2-hydroxy-5-methylbenzylidene)benzohydrazide and N′-(3-bromo-5-chloro-2-hydroxybenzylidene)-2-chlorobenzohydrazide, respectively. The complexes were characterized by physicochemical and spectroscopic methods and also by single-crystal X-ray determination. The hydrazone ligands coordinate to the Mo atoms through their phenolate O, imine N and enolic O atoms. The Mo atoms are six-coordinated in octahedral geometries. The complexes show high catalytic activities and selectivities in the epoxidation of cyclohexene with tert-butylhydroperoxide as primary oxidant.     

Two mononuclear molybdenum(VI) oxo complexes with tridentate hydrazone ligands: Synthesis,structures, and thermal stability

A reaction of [MoO₂(acac)₂] (where acac = acetylacetonate) with two hydrazone ligands in methanol yields two mononuclear molybdenum(VI) oxo complexes with the general formula [MoO₂L(CH₃OH)], where L = L¹=(4-nitrophenoxy)acetic acid [1-(5-chloro-2-hydroxyphenyl)methylidene]hydrazide (H₂L¹) and L = L²=4-dimethylaminobenzoic acid [1-(2-hydroxy-3-methoxyphenyl)methylidene]hydrazide (H₂L²). The crystal and molecular structures of the complexes are determined by the single crystal X-ray diffraction method. All of the investigated compounds are further characterized by the elemental analysis, FT-IR spectra, and thermogravimetric analysies. Single crystal X-ray structural studies indicate that hydrazone ligands coordinate to MoO₂ cores through enolate oxygen, phenolate oxygen, and azomethine nitrogen atoms. The Mo atoms in both complexes are in octahedral coordination.     

Synthesis,Spectral Characterization of Polymeric Nickel(II) Tetrathiocyanato Diargentate(I) Complexes with Some Acylhydrazones and Their Bio-activity

Polymeric heterobimetallic complexes of the type Ni[Ag(SCN)₂]₂.L (where L = acetophenone benzoylhydrazone (abh), acetophenone isonicotinoyl hydrazone (ainh), acetophenone salicyloyl hydrazone (ash), acetophenone anthraniloyl hydrazone (aah), p-hydroxy acetophenone benzoylhydrazone (phabh), p-hydroxy acetophenone isonicotinoyl hydrazone (phainh), p-hydroxy acetophenone salicyloyl hydrazone (phash) and p-hydroxy acetophenone anthraniloyl hydrazone (phaah) were synthesized and characterized with the help of elemental analyses, electrical conductance, magnetic moment, electronic and IR spectra, thermal and X-ray diffraction studies. Nickel(II) in the complexes has spin-free octahedral geometry. The hydrazone ligands are bi-coordinate bonding through > C═O and > C═N-groups. The complexes form a polymeric structure by bridging SCN groups between two metal centers. Thermal studies (TGA and DTA) on Ni[Ag(SCN)₂]₂.ash indicate multi-steps decomposition pattern which are both exothermic and endothermic. X-ray powder diffraction parameters for Ni[Ag(SCN)₂]₂.ash and Ni[Ag(SCN)₂]₂.phainh correspond to tetragonal and orthorhombic crystal lattices respectively. The ligands, as well as their complexes, show significant antifungal and antibacterial activity. The metal complexes are more active than the parent ligands.     

Synthesis and Rearrangement of Mono and Bis-(p-Fluorophenyl)Hydrazones of Dehydro-L-Ascorbic Acid

Abstract

The mono- and bis-(p-fluorophenyl)hydrazones of dehydro-L-ascorbic acid were prepared. Oxidation of the bis(hydrazone) afforded 3,6-anhydro-3-C-(p-fluorophenylazo) L-xylo-2-hexul osono-1,4-1 actone-2-(p-fluorophenyl)hydrazone. Rearrangement of the bis(hydrazone) gave T-(p-fluorophenyl)-3-(L-threo-glycerol-1-yl)-pyrazoli n-4,5-di one-4-(p-fluorophenyl)hydrazone, whose periodate oxidation gave 3-formyl-1-(p-fluorophenyl pyrazol in-4.5-dione-3-4-(p-fluorophenyl)hydrazone that upon reduction gave 1-(p-fluorophenyl)-3-hydroxymethyl pyrazol in-4,5-dione-4-(p-fluorophenyl)hydrazone. The compounds were characterized as their acetates and benzoates.     

Structural similarities among eight benzoylhydrazones

The crystal structures of eight benzoylhydrazones with different substituents have been investigated, namely 1‐benzoyl‐2‐(propan‐2‐ylidene)hydrazone, C₁₀H₁₂N₂O, (I), 1‐benzoyl‐2‐(1‐cyclohexylethylidene)hydrazone, C₁₅H₂₀N₂O, (II), 1‐benzoyl‐2‐[1‐(naphthalen‐2‐yl)ethylidene]hydrazone, C₁₉H₁₆N₂O, (III), 1‐benzoyl‐2‐(1‐cyclohexylbenzylidene)hydrazone, C₂₀H₂₂N₂O, (IV), 1‐benzoyl‐2‐(1‐phenylbenzylidene)hydrazone, C₂₀H₁₆N₂O, (V), 1‐benzoyl‐2‐[1‐(4‐chlorophenyl)benzylidene]hydrazone, C₂₀H₁₅ClN₂O, (VI), 1‐benzoyl‐2‐(4‐hydroxybenzylidene)hydrazone methanol monosolvate, C₁₄H₁₂N₂O₂·CH₃OH, (VII), and 1‐benzoyl‐2‐(1,1‐diphenylpropan‐2‐ylidene)hydrazone, C₂₂H₂₀N₂O, (VIII). The ten molecules in the eight crystal structures [there are two independent molecules in the structures of (V) and (VI)] show similar conformations and hydrogen‐bonding patterns. The C=N—NH—C=O group is planar, but the plane of the phenyl ring of the benzoyl group is rotated by about 30° with respect to that of the keto group [except for (IV), where the groups are coplanar]. Only in the amide group of (VIII) is the N—H group syn to the C=O bond, whereas the seven other compounds exhibit the anti conformation. Unless prevented by steric hindrance, N—H...O hydrogen bonds help to stabilize the crystal structure, which leads to infinite chains or dimers depending upon the molecular conformation. The molecular packing is supported by intermolecular C—H...O interactions. In the crystal structure of (VII), the methanol solvent molecule participates in two strong hydrogen bonds and two weak C—H...O interactions, thus acting as a link between the molecular chains.     

The optical sensor fac-tri­carbonyl­chloro­(di-2-pyridyl­methanone p-nitro­phenyl­hydrazone)­rhenium(I) di­methyl sulfoxide solvate

The first metal complex of di-2-pyridyl­methanone p-nitro­phenyl­hydrazone (dpknph), i.e. the title compound, fac-[ReCl(C₁₇H₁₃N₅O₂)(CO)₃]·C₂H₆OS, crystallizes as well separated pseudo-tetrahedral DMSO (DMSO is di­methyl sul­foxide) and pseudo-octahedral fac-[ReCl(dpknph)(CO)₃] moieties. Two N atoms from dpknph, three C atoms from the carbonyl groups and one chloride ion occupy the coordination sphere around rhenium. The coordinated dpknph ligand forms a six-membered ring in a boat conformation, with the pyridine rings in a butterfly formation. The p-nitro­phenyl­hydrazone moiety is planar, with all C and N atoms in sp²-hybridized forms. The mol­ecules pack as stacks of interlocked fac-[ReCl(dpknph)(CO)₃]·DMSO units via a network of non-covalent bonds that include solute–solute, solvent–solute and π–π interactions.     

Copper(II) complexes based on 2-thenoyltrifluoroacetone aroyl hydrazones: Synthesis,spectroscopy, and X-ray diffraction analysis

Copper(II) complexes CuL ? NH₃ are synthesized by the interaction of ethanol solutions of parasubstituted 2-thenoyltrifluoroacetylmethane aroyl hydrazones (H₂L¹–H₂L⁴) and an aqueous-ammonia solution of copper(II) acetate in an equimolar ratio. The copper(II) complexes are studied by elemental analysis, IR spectroscopy, and EPR spectroscopy. Single crystals of CuL³ ? NH₃ are grown from 1-(2-thenoyl)- 3,3,3-trifluoroacetone para-methylbenzoyl hydrazone and studied using X-ray diffraction analysis (CIF file CCDC 1045841).     

Synthesis of N,N-Disubstituted Lactone Hydrazones via (Sulfonylimino)-ethers

The dihydropyran 3 reacts with sulfonyl azides to give the known (sulfonylimino)-ethers ( = lactone sul-fonylimines) 4 and 18 . Reaction of 4 with NH₂NH₂ · H₂O leads to the aminoiriazole-dibulanol 5 , characterized as its tetraacetate 8 , and not, as previously claimed, to 6 or 7 . Similarly, the dihydrofuran-derived (tosylimino)-ether 10 yields 11 The structure of 5 was established by X-ray analysis, and a mechanism for its formation is proposed. Reaction of 4 with NH₂NMe₂ afforded the lactone hydrazone 16 and the hydrazidine 17. Catalysis by imidazole suppressed the formation of 17 similarly, the [(trifluoromethyl)sulfonyl]imine 18 yielded 16, and, by reaction with NH₂N(Me)Ph or 4-amino-4H-1,2,4-triazole, the lactone hydrazone 19 and the adduct 20 , respectively. The 1,4-lactone hydrazone 21 was obtained from 10 or from 22 . The structure of 20 was established by X-ray analysis. Treatment of 16 with BuLi followed by BnBr yielded the α-alkylated lactone hydrazone 23 .     

N′-(3-Bromo-2-hydroxybenzylidene)isonicotinohydrazide and its oxovanadium(V) complex: synthesis,structures, and catalytic properties

A new hydrazone N′-(3-bromo-2-hydroxybenzylidene)isonicotinohydrazide (H₂L) and its oxovanadium(V) complex, [VOLL′]·2H₂O (L′ = 2-hydroxybenzohydroxamate), were prepared and structurally characterized by physico-chemical, spectroscopic methods, and single-crystal X-ray determination. The hydrazone coordinates to V through the phenolate oxygen, imino nitrogen, and enolate oxygen. The hydroxamate coordinates to V through the carbonyl oxygen and deprotonated hydroxyl oxygen. Vanadium in the complex is octahedral. The oxidation of olefins with the complex as catalyst was evaluated, which indicated that the complex showed catalytic efficiency in oxidation of several aliphatic and aromatic substrates under mild conditions, using tert-butyl hydrogen peroxide as oxidant.     

15N NMR study of azo-hydrazone tautomerism of 15N-labelled azo dyestuffs

¹⁵N chemical shifts of 3-methyl-1-phenylpyrazole-4,5-dione 4-phenylhydrazone (1), 4-hydroxyazobenzene (2), 2-hydroxy-5-tert-butylazobenzene (3) and 1-phenylazo-2-naphthol (4), monolabelled with ¹⁵N at α-(compounds prepared from ¹⁵N-aniline) and β-positions (compounds prepared from Na¹⁵NO₂), have been measured and the temperature dependence of these chemical shifts followed between 240 and 360 K. For 4, representing a mixture of the azo and hydrazone forms, the hydrazone content has been calculated from the ¹⁵N chemical shifts of both nitrogen atoms at various temperatures. The two calculations gave identical results.