Synthesis and structure determination of pyrazine-containing macrocyclic polyazomethines

Two pyrazine-containing macrocyclic polyazomethines 2 and 3 were synthesized by direct [2 ＋ 2] and [3 ＋ 3] condensation reactions between 2,21-[pyrazine-2,3-diylbis（oxy）]dibenzaldehyde （1） and hydrazine. Both 2 and 3 were characterized by NMR, HRMS, and their structures were determined via X-ray crystal diffraction studies.

Survey of recent advances of in the field of π-conjugated heterocyclic azomethines as materials with tuneable properties

This account gives an overview of our recent work in the area of conjugated azomethines derived from 2-aminothiophenes.It will be presented that mild reaction conditions can be used to selectively prepare symmetric and unsymmetric conjugated azomethines.It further will be demonstrated that azomethines consisting of various 5-membered aryl heterocycles lead to chemically,reductively,hydrolytically,and oxidatively robust compounds.The optical and electrochemical properties of these materials can be tuned contingent on the degree of conjugation,type of aryl heterocycle,and by including various electronic groups.The end result is materials having colors spanning 250 nm across the visible spectrum.These colors further can be tuned via electrochemical or chemical doping.The resulting doped states have high color contrasts from their corresponding neutral states.The collective opto-electronic properties and the means to readily tune them,make thiophenoazomethine derivatives interesting materials for potential use in a gamut of applications.

Spectrophotometric Determination of Trace Amounts of Vanadium(Ⅴ) by Means of Its Catalytic Effect on Oxidation of Azomethine-H by Bromate

A new selective and sensitive kinetic method for determination of trace amounts of vanadium(Ⅴ) (0.5～40ng/ml) based on its catalytic effect on the oxidation of azomethine H by bromate at pH 4.2 and 25 ℃ was reported and its reaction mechanism was studied.The reaction was monitored spectrophotometrically by measuring the increase in absorbance of oxidation product of azomethine H at 436 nm after a fixed time ( 5 min ).The detection limit of the method is down to 2.0×10 -10 g/ml and the relative standard deviation (RSD) for 30 ng/ml of V(Ⅴ) is 0.26 % ( n =6). The effect of foreign ions on V(Ⅴ) determination was also discussed,and the method is mostly free from interferences of other ions.The proposed method was successfully applied to the determination of trace amounts of vanadium in water samples.

New Azomethine Compounds on the Basis <i>m</i>-Phenylenediamine and Substituted Benzaldehydes Capable of Oxidative Polymerization

Low-temperature condensation of m-phenylene diamine and various aromatic aldehydes (benzaldehyde, m-, o-nitrobenzaldehyde, p-diethylaminobenzaldehyde, o-, p-hydroxybenzaldehyde and 4-hydroxy-3,5-ditert-butylbenzaldehyde) in the ethyl alcohol medium synthesized new azomethine compounds. With the help of spectral methods and elemental analysis, the structure of the azomethine compounds obtained was confirmed. It was founded that irradiation of azomethine compounds with UV light at a wavelength of 300 - 330 nm results in their emission. The luminescent properties of the resulting compounds are due to the presence of chromophore azomethine groups in the molecule structure. In particular, the π-electrons of the azomethine bonds can undergo irradiation to a different energy levels, accompanied by fluorescence. It was shown that synthesized azomethine compounds are capable of oxidative polymerization. Based on azomethine compounds in hydrochloric acid solution synthesized polymers with conjugated bonds, which had low molecular-mass characteristics. It is shown that the oxidative polymerization of azomethines proceeds through a slow (one-electron transfer) and rapid (recombination of the radical cations) stage.

Synthesis and Electrochemical Characterization of Azomethine Containing N-Ethylcarbazole Group

Conjugated aromatic azomethines containing a carbazole group were synthesized. Their structures have been confirmed by IR, MS and UV spectrometries. When iodine was used as the dope to the conjugated compounds, the electrical conductivities （EC） of the doped conjugated compounds were increased by several orders of magnitude. The thermal stability of these two compounds investigated by TGA shows a good result, which guarantees the correct result of EC when the compounds are heated. As can be seen from the CV characterization of the electrochemical properties of these two compounds, the azomethine diamine and p-aminophenyl-9-ethylcarbazolyl azomethine possess electrochemical activity, which arises from the heteroatom of molecules.

MELTING AND CRYSTALLIZATION BEHAVIOR OFAN AROMATIC POLY (AZOMETHINE ETHER) WITH NON-LINEARLY SHAPED MOLECULAR CONFORMATIONS

The melting and crystallization behavior have been investigated for an aromatic poly (azomethine ether)with non-linearly shaped molecular conformations. This polymer was found to undergo multiple melting processes and its phase transition behavior was influenced sensitively by the thermal history of sample. A significant difference between the polymer chain aggregation abilities of samples cooled from the different states was observed. The possible molecular morphology and aggregation models for describing the structures of this polymer were proposed and discussed. The crystallization behavior of the samples cooled from the partially isotropic state and the influence of cooling rate on it have also been examined with DSC.

Synthesis and Crystal Structure of 1-Ethyl 3-Methyl 6-Benzyl-2-methyl-5-oxo-5,6-dihydropyrrolo[1,2-c]quinazoline-1,3-dicarboxylate

The crystal structure of the title compound（C24H22N2O5, Mr = 418.44） has been determined by single-crystal X-ray diffraction. The crystal is of orthorhombic, space group P21/c with a = 7.751（2）, b = 12.392（4）, c = 21.326（6）, V = 2048.4（1）3, Z = 4, Dc = 1.357 g/cm3, F（000） = 880, μ（MoKα） = 0.096 mm-1, the final R = 0.0731 and wR = 0.1982 for 3335 observed reflections（I 〉 2σ（I））. Intermolecular C（24）–H（24B）···O（1） hydrogen bond is observed in the structure.

Synthesis and Crystal Structure of 3′-Ethyl 5′-Methyl 1-Benzyl-4′-methyl-2-oxo-3′,4′-dihydrospiro-[indoline-3,2′-pyrrole]-3′,5′-dicarboxylate

The crystal structure of the title compound（C24H24N2O5, Mr = 420.45） has been determined by single-crystal X-ray diffraction. The crystal is of triclinic, space group P1 with a = 8.991（1）, b = 11.166（1）, c = 11.169（1） , α = 91.413（2）, β = 105.887（2）, γ = 90.992（2）°, V = 1077.8（2） 3, Z = 2, Dc = 1.296 g/cm^3, F（000） = 444, μ（MoKα） = 0.091 mm^-1, the final R = 0.0466 and wR = 0.1507 for 4185 observed reflections（I 〉 2σ（I））. The single-crystal X-ray diffraction data indicated intermolecular C（17）–H（17）O（4）, C（5）–H（5）… O（4） hydrogen bonds and C–H…π interaction in the structure.

Examination of Polymeric Azomethine Compounds and Their Transition Metal Complexes by Using XRF and XRD Technique

In this study,the electronic transition properties and structural analysis of the metal complexes(Ni(Ⅱ),Co(Ⅱ),Cu(Ⅱ)and Mn(Ⅱ))of three different polymer ligands were performed by using XRF and X-ray diffraction(XRD)techniques,respectively.The structural analysis of the polymers and their complexes were performed by XRD technique and some of the polymers were found to be in the face-centred cubic(fcc)structure.In addition,the values of the present K X-ray intensity ratios are significantly greater than the values reported in literature.

Solution Processable Material Derived from Aromatic Triazole, Azomethine and Tris: Preparation and Hole-Buffering Application in Polymer Light-Emitting Diodes

This work presents the synthesis of a new hole-buffering material TAZS and its successful application in polymer light-emitting diodes to enhance device performance. The TAZS is composed of aromatic 1,2,4-triazolylcore linked with three trihydroxy tert-butyl terminals via azomethine linkages. The TAZS forms ashomogeneous film deposited by spin-coating process. The HOMO and LUMO levels of TAZS are -5.23 eV and -2.40 eV, respectively, as estimated from cyclic voltammogram. The current density results of hole-only and electron-only devices confirm strong hole-buffering capability of TAZS layer. Multilayer PLEDs with different thickness of TAZS (ITO/PEDOT: PSS/TAZS (x nm)/SY/ETL/LiF/Al) have been successfully fabricated, using spin-coating process to deposit hole-injecting PEDOT: PSS, TAZS, and emissive SY layers. The PLED with 16 nm TAZS reveals the optimal device performance, with maximum luminance and maximum current efficiency of 19,046 cd/m2 and 4.08 cd/A, respectively, surpassing those without TAZS as HBL (8484 cd/m2, 2.13 cd/A). The hole-buffering characteristic of TAZS contributes greatly to improved charges’ recombination ratio and enhanced emission efficiency.

Synthesis, Characterization and Metal Ion Adsorption Studies on Novel Aromatic Poly(Azomethine Amide)s Containing Thiourea Groups

A series of novel ladder-type poly(azomethine amide)s (PAMs) were prepared from new azomethine containing carboxylic acid monomer (TCA) with simple aromatic diamines and aromatic diamines with thiourea groups (TDAs) by means of phosphorylation polycondensation reaction. Molecular weights of the polyamides were evaluated viscometrically, and the inherent viscosities were in the range of 0.31 - 0.58 g/dl. These ladder-type polymers were not freely soluble in common organic solvents. Structure of monomers and polymers were confirmed using FT-IR, 1H-NMR and 13C-NMR spectroscopic analysis. Removal of Cu2+ and Cd2+ from aqueous solutions by adsorption onto the polyamides was investigated. The effect of pH, initial metal ion concentrations and contact time were studied in batch experiments. The polyamides were found to be highly effective adsorbents for the removal of Cu2+ and Cd2+ metal ions from aqueous solutions. In a mixture of metal ions, the selectivity order was found to be Pb(II) > Cu(II) > Cr(IV) > Cd(II).

Synthesis and Characterization of Poly(azomethine ester)s with a Pendent Dimethoxy Benzylidene Group

Recently, soluble poly(azomethine ester)s with good thermal stability and liquid crystalline properties are much sought after in opto-electronic field. One such attempt was to synthesize poly(azomethine ester)s with a pendent group. In this study, the newly synthesized diacid monomer benzalaniline 3’-4’dimethoxy terepthalic acid was condensed with two diol monomers to get the polymers with pendent benzylidene group. The diacid monomer was characterized by UV, IR, NMR and CHNS analysis. The polymers were characterized by IR, TGA, and for liquid crystalline property. Polymer-I showed the highest thermal stability upto 335°C. Polymer-II exhibited liquid crystalline nature along with good solubility and thermal stability.

1,3-Dipolar Cycloaddition of Polycyclic Aromatic Azomethine Ylides and Alkynylbenziodoxoles for Synthesis of Functional Dibenzoullazines

A new family of dibenzoullazine derivatives was synthesized through 1,3-dipolar cycloaddition of polycyclic aromatic azomethine ylides with alkynylbenziodoxoles followed by oxidation.The benziodoxole moiety in the resulting products was used as a versatile linchpin for the synthesis of structurally diverse functional dibenzoullazines that are difficult to access by other synthetic methods.

Catalyst-free and atom-economical [4+3] cycloaddition of azadienes with cyclic azomethine imines for facile synthesis of 1,2,4-triazepines

A catalyst-free and atom-economical[4+3]cycloaddition of azadienes with C,N-cyclic azomethine imines has been developed,providing an efficient and environmentally benign access to 1,2,4-triazepines with high diastereoselectivities and yields.This reaction can be performed in 2-methyltetrahydrofuran under mild conditions smoothly.

Pyridine-Fused Azacorannulene:Fine-Tuning of the Structure and Properties of Nitrogen-Embedded Buckybowls

Heteroatom-embedded buckybowl molecules provide a fundamental molecular framework that has potential applications in various research fields.However,selective introduction of heteroatoms into buckybowls is challenging,and thus,studies investigating the effect of introduced heteroatoms have been limited.Here,we report the synthesis of pyridine-fused azacorannulene molecules.The influence of nitrogen atoms introduced into the peripheral positions on the structural,electronic,and optical properties is discussed.

A New Method of Synthesis of Azo Schiff Base Ligands with Azo and Azomethine Donors： Synthesis of N-4-Methoxybenzylidene-2-（3-hydroxyphenylazo）-5-hydroxyaniline and Its Nickel（Ⅱ） Complex

A new method for the synthesis of azo Schiff an base ligand in which the azo and azomethine groups are coordination sites was developed through a Schiff base precursor. The precursor, N-4-methoxybenzylidene-3-hydroxyphenylamine （SB） derived from 3-aminophenol was regioselectively coupled with a diazonium ion para to the hydroxyl group of the amine component of the Schiff base. The para selectivity was controlled by the directing effect of the hydroxyl group. The ligand and its nickel（Ⅱ） complex were characterized by elemental analyses, IR and UV-Vis spectroscopy. The analytical and spectral data supported the mononuclear formulation of the complex with metal to ligand ratio （M ： L = 1 ： 2） and suggested a square planar geometry for the complex.

New Insights on the Mechanism of Thermal Cleavage of Unsaturated Bicyclic Diaziridines： A DFT Study

A DFT calculations are carried out at UB3LYP/6-311＋ ＋G （3df, 2p） levels of theory to study electrocyclic thermal cleavage of four （R） derivatives of unsaturated bicyclic diaziridines, Ix-R, to produce corresponding （Z） and （E） azomethine imides （2X-Z, 2X-E, 3X-Z and 3X-E）, where X=H, Me, t-Bu and Ph. Cleavage of 1X-R series to form the most stable 3X-Z product, （path 2） is found the favored procedure because of delocalized negative charge on five atoms and lower steric effect in related transition state. According to IRC calculations in paths 1 and 2, C6--N1 bond is cleaved before the rate determinating step （transition state）. The stability of unsaturated bicyclic diaziridines and their corresponding （Z） and （E） azomethine imides is in the following order in gas phase and chloroform, tetrahydrofuran, and acetone solvents： 3X-Z〈3X-F〈2X-Z 〈2X-E 〈 1X-R 〈 1X-S.

Synergistic Catalysis with Azomethine Ylides

Azomethine ylides are useful intermediates for the rapid construction of chiral N-containing compounds.However,its synthetic potential has not been fully developed due to the limited reaction models.In combination with synergistic catalysis and azomethine ylide chemistry,we have developed several types of novel catalytic system including Cu/Pd,Cu/Ir and PTC/Ir catalysis;which can convert readily-available azomethine ylides to various high-valued molecules such as unnatural a-amino acids,homoallylic amines and N-heterocycles.Compared with the traditional mono-catalysis,the synergistic catalyst system exhibits enhanced catalytic efficiency and chiral induction ability in many cases.In addition,we have demonstrated that these strategies could be applied in the construction of bioactive compounds and natural products.

A Facile Access to Fluorinated Pyrrolidines via Catalytic Asymmetric 1,3-Dipolar Cycloaddition of Azomethine Ylides with Methyl a-Fluoroacrylate

Asymmetric 1,3-dipolar cycloaddition of methyl a-fluoroacrylate with azomethine ylides for the construction of optically active fluorinated pyrrolidines bearing one unique fluorinated quaternary and two tertiary stereogenic cen- ters has been achieved with Cu（CH3CN）4BF4/TF-BiphamPhos complexes for the first time. This catalytic system performs well over a broad scope of substrates, providing the synthetically useful adducts in good yields and excel- lent diastereoselectivities and good to high enantioselectivities.

Mesomorphic behavior of new azomethine liquid crystals having terminal iodo group

A series of azomethine esters,3-hydroxy-4-{[（4-iodophenyl）imino]methyl}phenyl alkanoates possessing even number of carbon atoms at the terminal alkanoyloxy chain（C_（n-1）H_（2n-1）COO-,n = 4,6,8,10,12,14） was synthesized.n-Butanoyloxy was found non-mesogenic,whilst n-hexanoyloxy to n-tetradecanoyloxy exhibited enantiotropic smectic A phase with fan-shaped texture.It was found that the length of terminal alkanoyloxy chain influenced the mesomorphic properties.