Hydrazone Unit Research Articles

New chromogenic bis(isatin hydrazonyl)calix[4]arenes for dual recognition of fluoride and silver ions

New calixarene based dual chromogenic receptors bearing isatin hydrazone units have been synthesized and evaluated for their ion recognition potential. The synthesized molecular receptors can effectively and selectively recognize fluoride and silver ions through visible color changes and pronounced bathochromic shifts in their UV–visible spectra. NMR titration data further support the preliminary conclusions.

Ferrocene-based compartmental ligand for the assembly of neutral ZnII/LnIII heterometallic complexes

A ferrocene-based compartmental ligand, H2L, was synthesized by the reaction of diacetyl ferrocene with hydrazine hydrate followed by a condensation reaction with o-vanillin. [L](2-) possesses a dual coordination pocket, an inner pocket of 2 imino nitrogens and two phenolate oxygens and an outer pocket of two phenolate and two methoxy oxygen atoms. Utilizing this ligand, several Zn(II)/Ln(III) heterobimetallic complexes were assembled: [LZn(μ-OAc)Dy(NO3)2] (2), [LZn(μ-OAc)Tb(NO3)2] (3), [LZn(μ-OAc)Gd(NO3)2·2CHCl3] (4), [LZn(μ-OAc)Er(NO3)2] (5), [LZn(μ-OAc)Ho(NO3)2] (6), [LZn(μ-OAc)Eu(NO3)2] (7). All of these metal complexes are neutral and isostructural: the Zn(II) ion occupies the inner coordination pocket while the Ln(III) ion occupies the outer coordination pocket of the doubly deprotonated ligand [L](2-). Zn(II) has a coordination number of 5 (2N, 3O) in a square pyramidal coordination geometry while Ln(III) has a coordination number of 9 (9O) in a distorted tricapped trigonal prismatic geometry. Zn(II) and the 4f metal ion are bridged to each other by two phenolate oxygen atoms and an acetate ligand. ESI-MS reveals that 2-7 retain their structural integrity in solution. Cyclic voltammetry of 1-7 revealed a quasi-reversible oxidation (involving the ferrocene motif) and an irreversible reduction of the hydrazone unit. Magnetic studies of 2, 3 and 6 were carried out. Ac susceptibility studies did not reveal slow relaxation of magnetization.

Synthesis of Hydrazone‐Modified Nucleotides and Their Polymerase Incorporation onto DNA for Redox Labeling

Abstract5‐(5‐Formylthiophen‐2‐yl)cytosine, 7‐(5‐formylthiophen‐2‐yl)‐7‐deazaadenosine 2′‐deoxyribonucleosides, and their 5′‐O‐triphosphates (dNTPs) were converted into the 2,4‐dinitrophenylhydrazone or nitrobenzofurazanyl. The hydrazone‐modified dNTPs were enzymatically incorporated into DNA by polymerase catalyzed primer extension (PEX). This direct incorporation of hydrazone‐linked dNTPs was compared to previously reported incorporation of aldehyde‐modified dNTPs followed by postsynthetic hydrazone formation on DNA to show that the direct incorporation can be used for incorporation of more hydrazone units, however, cleaner PEX products are formed by incorporation of aldehydes and subsequent reaction with hydrazines. Extensive study of electrochemical behavior of the nitroarylhydrazone‐linked nucleosides and DNA was performed confirming the potential utility of the hydrazone, nitroaryl, and benzofurazane groups for redox labeling of DNA.

Octahedral Complexes of Cobalt(III) and Nickel(II) Incorporating with Unsymmetrical NNO-Donor Hydrazone Ligand: Synthesis and Structural Aspects

Two new octahedral cobalt(III) and nickel(II) complexes, [CoL2]·ClO4 (1) and [NiL2]·H2O·NO3 (2) containing the potentially tridentate Schiff base like hydrazone ligand, N′-[1-(pyridin-2-yl)ethylidene]acetohydrazide (L) (1:1 condensation product of acetichydrazide and 2-acetylpyridine) were synthesized and characterized by spectral a well as thermal analysis and single crystal X-ray diffractometry. Structural investigation shows that in both complexes, the central Co or Ni atom belongs into N4O2 coordination sphere, developed with the NNO donor sets of two independently hydrazone units. The corresponding M–N(pyridine) bonds being significantly longer than the M–N(imino) bonds, Co1–N1 and Co1–N4 [1.934(3) and 1.926(3) A] for 1 and Ni1–N1 and Ni1–N4 [2.076(3) and 2.085(3) A] for 2, Co1–N2 and Co1–N5 [1.846(3) and 1.854(3) A] for 1 and Ni1–N2 and Ni1–N5 [2.001(3) and 1.972(3) A] for 2 respectively. Two new octahedral cobalt(III) and nickel(II) complexes containing the potentially tridentate hydrazone ligand, N’-[1-(pyridin-2-yl)ethylidene]acetohydrazide (L) were synthesized and characterized by IR and UV–Vis spectra as well as thermal analysis and single crystal X-ray diffractometry.

Supramolecular [M4L4] Tetrahedra Based on Triangular Acylhydrazone Catechol Ligands

AbstractThe ligands 1‐H6 and 2‐H6 are prepared by condensation of the triangular triamines 5 and 2,3‐dihydroxybenzoic acid hydrazide 7. The ligands form container‐type tetrahedral coordination compounds Mx [(1 or 2)4M′4] (M = Li, Na, K; M′ = Ti, x = 8; M′ = Ga, x = 12). The complexes are characterized by NMR spectroscopy and ESI mass spectrometry. Despite the relatively labile acyl hydrazone unit, the complexes show high stability in water. Ligand 3‐H6 is prepared from the trisacyl hydrazide 8 and 2,3‐dihydroxybenzaldehyde 9 but does not form well‐defined coordination compounds with gallium(III) or titanium(IV) ions.

Calix[4]arene-based ditopic receptors for simultaneous recognition of fluoride and cobalt(II) ions

A series of calix[4]arene based ditopic receptors possessing bipyridyl and hydrazone units have been synthesized and evaluated for ionic recognition. It has been observed that the synthesized derivatives function as allosteric receptors for simultaneous recognition of Co2+and F− ions through non-covalent interactions. Significant bathochromic shifts in the UV–visible spectrum with a profound colour change promise their use to engineer novel applications.

ChemInform Abstract: Synthesis, Characterization and Photochromic Properties of Novel Naphthopyrans with Hydrazone Unit Residue.

AbstractAll new compounds (I) possess good photochromic properties and high fatigue resistance.

Synthesis, Characterization and Photochromic Properties of Novel Naphthopyrans with Hydrazone Unit Residue

AbstractA series of naphthopyrans with hydrazone unit (8a–8m), were synthesized and characterized by 1H NMR, 13C NMR, IR and HRMS. The photochromic properties were investigated under continuous irradiation, in particular regard to the fatigue resistance and the lifetime of the colored open form in solution and polymers. The results showed that these compounds had both good photochromic properties and high fatigue resistance. Detailed studies showed that representative compound 8d (3,3‐di‐4‐methoxybenzoic acid methylenehydrazino‐[3H]‐naphtho [2,1‐b]pyran) had good photochromic properties in THF solution, in solid state, and in polymers, and exhibited a significant bathochromic shift in the spectra of the open forms compared to known naphthopyrans 9 (3,3‐diphenyl‐[3H]‐naphtho[2,1‐b]pyran). On the other hand, the higher melting points of target compounds are promising for the polymer film preparation through hot‐melt method.

(1E)-1-(3-Bromophenyl)ethanone 2,4-dinitrophenylhydrazone

The title compound, C14H11BrN4O4, contains 3-bromo­phenyl and 2,4-dinitro­phenyl groups on opposite sides of a hydrazone unit and crystallizes with two mol­ecules in the asymmetric unit. The dihedral angles between the two ring systems in each mol­ecule are 2.0 (1) and 2.5 (4)°. Weak C—H⋯O hydrogen bonds and weak π–π stacking inter­actions [centroid–centroid distance = 3.7269 (14) Å] help to establish the packing. Intra­molecular N—H⋯O hydrogen bonds are also observed. On one of the rings, the Br atom is disordered over two equivalent positions of the phenyl ring [occupancy ratio 0.8734 (10):0.1266 (10).

Synthesis, characterization, thermal, and redox properties of a vic-dioxime and its metal complexes

A new vic-dioxime ligand containing benzophenone hydrazone units, N′-(benzophenone hydrazone)glyoxime [LH2] has been prepared from benzophenone hydrazone and anti-chloroglyoxime in absolute ethanol. Mononuclear nickel(II), cobalt(II), copper(II), zinc(II), and cadmium(II) complexes were also synthesized. Ligand and complexes were characterized by elemental analyses, FT-IR, 1H NMR, and 13C NMR spectroscopy, magnetic moments, and DTA/TG techniques. On the basis of the magnetic and spectral evidences a square-planar geometry for Ni(II) and Cu(II) complexes, tetrahedral for Cd(II) and Zn(II) complexes, and octahedral for Co(II) complex were proposed. Redox behaviors of ligand and its complexes were also investigated by cyclic voltammetry at the glassy carbon electrode.

Control of Relative Direction and Amplitude in Extension/Contraction Motions of Molecular Strands Induced by Ion Binding

The shape of ligand strands composed of six-membered aza-heterocycles (het) connected at the alpha and alpha' positions by hydrazone (hyz) units is determined in a predictable fashion by the nature of the heterocyclic groups (pyridine, pyrimidine, pyrazine etc.), and covers the range from extended linear to compact helical structures. The binding of metal ions to the coordination subunits, defined by the het-hyz sequences, leads to marked shape changes by inter-converting bent and linear conformations of the subunits, thus inducing relative motions of strand domains either in the same (con-sense, "twirling") or in opposite (dis-sense, "flapping") directions. The amplitude of the motion induced by metal-ion binding and release and the relative directions of the formal motions can be controlled by the nature of the heterocyclic units. Thus, motions around a central 4,6-disubstituted pyrimidine are dis-sense motions, whereas there are con-sense motions around a central 2,5-disubstituted pyrazine unit, as illustrated by model ligands 1 and 2, respectively. The more extended helical 3 and undulating (zigzag shape) 4 ligands undergo larger-amplitude motions combining the relative displacements displayed by 1 and 2. Ligands 3 and 4 form linear tetranuclear Pb(II) and Zn(II) complexes, thus producing an extension motion. The same holds for [Ru(4)(terpy)(4)](PF(6))(8) (terpy=terpyridine). Reversible acid-base-triggered molecular motions have been generated with [Zn(4)(4)(OTf)(8)] (TfOH=triflic acid).

Crystal structure and properties of (Z)-N′-((E)-2-(hydroxyimino)-1-phenylethylidene) isonicotinohydrazide

Compound I contains in its molecule pyridyl, monoxime and hydrazone functions. A non-merohedral twin crystal of the compound with two reciprocal lattices differently oriented and giving rise to double diffraction spot sets with the 0.5:0.5 ratio of the twin components was studied. The hydrazone and oxime units are approximately planar. The dihedral angles between this plane and the planes of the pyridine and phenyl rings are 30.79(19)° and 18.43(13)°, respectively. Both the oxime and hydrazone units in I have an E configuration. The molecules of I are linked via C-H⋯O and O-H⋯N hydrogen bonds forming a 3D framework. The compound was also characterized by IR, 1H NMR and elemental analyses.

First phosphorous d-xylose-derived glycodendrimers

Phosphorous glycodendrimers have been prepared in quantitative yields by grafting xylose-derived moieties on phosphorous dendrimers involving hydrazone units. These dendrimers could be hydrophobic or amphiphilic, respectively, with acetylated or unprotected sugar moieties.

Self‐Assembly, Structure and Solution Dynamics of Tetranuclear Zn2+ Hydrazone [2×2] Grid‐Type Complexes

AbstractWe describe the self‐assembly processes as well as the structural and physico‐chemical properties of [2×2]Zn2+4 grid complexes involving the bis‐tridentate ligands 7–12, based on bis(hydrazone)pyrimidine complexation subunits and octahedrally coordinated Zn2+ ions. The NMR spectroscopic data and the X‐ray crystal structure results indicate that in solution and in the solid state the complexes 13–18 adopt a very compact arrangement providing stable [2×2] hydrazone‐grid arrays. The π–π stacking between the phenyl ring and the hydrazone units of the perpendicular ligands in the complexes induces a perfect orthogonal arrangement suitable for applications in self‐organized metallosupramolecular systems. Zinc complexes provide an opportunity to study the acid–base chemistry without the added effects due to paramagnetism or redox chemistry. The intermediate protonated grids undergo relatively rapid proton exchange on the NMR timescale, the presence of a sharp pyrimidine proton resonance suggesting that there is significant delocalization of the negative charge along the backbone of the ligand. Rotation of the phenyl ring is observed. It involves probably a mechanism in which one of the ligands partially dissociates allowing the initially intercalated phenyl group to rotate, before recoordination of the terminal pyridine. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Mixed‐Valence, Mixed‐Spin‐State, and Heterometallic [2×2] Grid‐type Arrays Based on Heteroditopic Hydrazone Ligands: Synthesis and Electrochemical Features

An extended family of heterometallic [(M1)2(M2)2(L-)4](n+) [2x2] grid-type arrays 1-9 has been prepared. The three-tiered synthetic route encompasses regioselective, redox and enantioselective features and is based on the stepwise construction of heteroditopic hydrazone ligands A-C. These ligands contain ionisable NH and nonionisable NMe hydrazone units, which allows the metal redox properties to be controlled according to the charge on the ligand binding pocket. The 2-pyrimidine (R) and 6-pyridine (R') substituents have a significant effect on complex geometry and influence both the electrochemical and magnetic behaviour of the system. 1H NMR spectroscopic studies show that the Fe(II) ions in the grid can be low spin, high spin or spin crossover depending on the steric effect of substituents R and R'. This steric effect has been manipulated to construct an unusual array possessing two low-spin and two spin-crossover Fe(II) centres (grid 8). Electrochemical studies were performed for the grid-type arrays 1-9 and their respective mononuclear precursor complexes 10-13. The grids function as electron reservoirs and display up to eight monoelectronic, reversible reduction steps. These processes generally occur in pairs and are assigned to ligand-based reductions and to the Co(III)/Co(II) redox couple. Individual metal ions in the heterometallic grid motif can be selectively addressed electrochemically (e.g., either the Co(III) or Fe(II) ions can be targeted in grids 2 and 5). The Fe(II) oxidation potential is governed by the charge on the ligand binding unit, rather than the spin state, thus permitting facile electrochemical discrimination between the two types of Fe(II) centre in 7 or in 8. Such multistable heterometallic [2x2] gridlike arrays are of great interest for future supramolecular devices incorporating multilevel redox activity.

Dimeric Rhenium(I) Carbonyl Complexes with Thiosemicarbazone Backbone

AbstractDimeric, neutral rhenium(I) complexes of the composition [Re2(CO)6X(LR)] (X = Cl or Br) are formed when [NEt4]2[Re(CO)3Br3] or [Re(CO)3Cl(CH3CN)2] react with 2, 2′‐dipyridylketone thiosemicarbazones (HLR, R = H, Ph). The thiosemicarbazones deprotonate during the reaction and connect two tricarbonylrhenium(I) units as formally pentadentate bridging ligands. This results in an extremely rare coordination mode, in which the two nitrogen atoms of the hydrazone unit bind to each one of the rhenium atoms. The bond lengths inside the thiosemicarbazonato backbone reflect a large degree of delocalization of electron density.

Novel Hydrazone Based Hole Transport Materials for Electrophotography

Monomeric, dimeric and polymeric hydrazone based hole transporting materials (TM) with the following structures were developed and evaluated for electrophotography.The general synthesis for all of these derivatives involves the reaction of the suitable aldehydes, having heterocyclic or aromatic chromophores (Ar), with the phenylhydrazine, followed by the reaction with epichlorohydrin. The dimeric and polymeric structures require an additional reaction step involving structures a-e (denoted as X above) to bind the hydrazone units into the dimeric structure or polymeric chain. The final products were purified several times and their structures were confirmed by H-NMR, C-NMR, and UV and IR spectra. The ionization potential (Ip) and hole mobility (using xerographic time of flight technique) were measured for all the compounds. The presence of oxiranyl or hydroxyl groups improves adhesion and compatibility not only with traditional polycarbonate (PC) binder material but also with polyvinylbutyral (PVB). Meanwhile, such dimeric or polymeric hole TM can be chemically cross-linked in the layer, for example, by reaction of the hydroxyl groups with polyisocyanates. Monomers with two oxiranyl groups can be cross-linked with polythiols. These TM properties increase the layer stability to bending, stretching and abrasion, as well as the effects of abrasion. The synthesized TM and compositions with binder exhibit good hole transporting properties and high mobility making them useful for preparation of high sensitivity electro-photographic photoconductors. They also can be used for preparation of bipolar transporting compositions and single layer photoreceptors.

Synthesis of polyhydrazones by diazo coupling reaction of bisacetoacetamides with diazonium salts

Hydrazone polymers were prepared by the diazo coupling reaction of bisacetoacetamides with diazonium salts under mild basic conditions. Bisacetoacetamides 1 and 2 having two 1,3-diketo groups were prepared by the reaction of aromatic diamines with diketene. Diazonium salts 3–5 were prepared by the reaction of aromatic diamines with nitrous acid in an aqueous HCl. A diazonium salt was isolated in a stable form after exchanging chloride with fluoroborate. The resulting polymer structure was determined by spectroscopic methods to be mainly polyhydrazone. The hydrazone unit was found stabilized by the intramolecular hydrogen bonding. The polymer obtained from 2 and 5 was soluble in organic solvents and showed the UV maximum peak at 376 nm in dimethyl sulfoxide.

Azo pigments and their intermediates. A new class of couplers for red and near-IR sensitive photogenerating azo pigments

The synthesis of azoic couplers, 2,8-dihydroxy-3-naphthanilide and its derivatives, by first converting 2,8-dihydroxy-3-naphthoic acid into its phenyl ester followed by condensing the phenyl ester with an aniline derivative, is reported. Photogenerating bisazo and trisazo pigments have been prepared by coupling 2,8-dihydroxy-3-naphthanilide with 2,7-diamino fluorenone and tris( p-aminophenyl)amine, respectively. The absorption spectra of these pigments are found to be red-shifted relative to analogous pigments synthesized from 2-hydroxy-3-naphthanilide. The data suggest that 2,8-dihydroxy-3-naphthanilides are new coupler components for red and near-IR absorbing photogenerating azo pigments. Evidence is provided that the red shift is a result of an intramolecular H-bonding between the 8-OH group in the coupler moiety and the nitrogen atom in the hydrazone unit of the pigment. Comparison of the pigments synthesized in this work with those from 2-hydroxy-11 H-benzo(si)carbazole-3-carboxanilides suggests that the wavelength extension achieved by carbazole-couplers may also be a H-bonding effect, between the N-H group in the carbazole ring and the nitrogen in the hydrazone unit. The advantage of using the couplers described in this work for preparing red and near-IR absorbing photogenerating pigments is discussed.

Lanthanide ion complexes of a ligand derived from salicylaldehyde and malonyl dihydrazone

The chelates Na 2[Ln(C 34H 28N 8O 8)Cl]· nH 2O of the malonyl dihydrazone of salicylaldehyde with the lanthanides have been prepared and characterized by elemental analysis, IR, UV, molar conductance and TGA. It is shown that the ligand coordinates to the central ion with one hydrazone unit in the keto form and one chloride ion participates in coordination to the metal ion. These chelates are 1:2 electrolytes in DMF and are more thermostable than their ligand due to the formation of chelate rings.