Synthesis,film-forming properties,and photosensitivity of 4-alkoxy(acyloxy)-3-alkoxyphenylmethylene-(biphenyl-4-yl)amines

The reactions of ethers and esters of the vanillin series with biphenyl-4-ylamine in absolute methanol yielded previously unknown E isomers of biphenyl-substituted azomethines (Schiff bases). The film properties and photosensitivity of the new compounds were examined.     

Selective cleavage of phenolic tert-butyldimethylsilyl ethers using simple organic nitrogen bases

<正>Simple organic nitrogen bases,such as Et_3N,pyridine,DBU,etc.,were found to be convenient and useful reagents for deprotection of TBDMS groups on acidic hydroxyl groups.The efficiency of these bases has an apparent order:1°amine2°amine3°amine and aliphatic basearomatic base.In aqueous DMSO and at room temperature,phenolic TBDMS ethers were removed selectively in the presence of alcoholic TBDMS ethers.And catalytic base can make these reactions complete.This method is high-yielding,fast,clean,safe and cost-effective.     

Quantification of derivatives of bisphenol A diglycidyl ether (BADGE) and novolac glycidyl ether (NOGE) migrated from can coatings into tuna by HPLC/fluorescence and MS detection

A reversed phase high performance liquid chromatographic method combined with fluorescence and mass spectrometric detection in series is presented for the separation and quantification of bisphenol A diglycidyl ether (BADGE) and novolac glycidyl ether (NOGE) derivatives in extracts from food can coatings, tuna and oil. Fifteen samples of tuna cans bought in four European countries were investigated. Atmospheric pressure chemical ionization mass spectrometry in the positive ion mode (APCI(+)-MS) allowed to tentatively identify BADGE and NOGE related compounds originating from reactions of the glycidyl ethers with bisphenols, phenol, butanol, water and hydrochloric acid. Quantification was based on the external standard method and fluorescence detection. Mass fractions up to 3.7 micrograms/g were found for hydrochlorination products of bisphenol F diglycidyl ether (BFDGE + 2HCl) in tuna. Furthermore, total migration quantities of phenolic ether compounds were estimated. The highest values found were 20 micrograms/g in tuna and 43 micrograms/g in the oil phase.     

双冠醚的研究(Ⅶ)——Schiff碱型和仲胺型双(苯并-18-冠-6)的合成

4′-氨基苯并-18-冠-6分别与间-硝基苯甲醛、对-硝基苯甲醛、间-苯二甲醛及其取代物和对-苯二甲醛缩合制得6种新的Schiff碱型单冠醚和双冠醚。4′-甲酰基苯并-18-冠-6分别与4′-氨基苯并-15-冠-5、4′-氨基苯并-18-冠-6作用制得2个醚环大小相同和不同的Schiff碱型双(苯并冠醚)。这些双冠醚经硼氢化钠还原得到相应的6种新的仲按型双冠醚。     

Synthesis, potentiometric and antimicrobial studies on metal complexes of isoxazole Schiff bases

The metal complexes of Cu(II), Ni(II) and Co(II) with Schiff bases of 3-(2-hydroxy-3-ethoxybenzylideneamino)-5-methyl isoxazole [HEBMI] and 3-(2-hydroxy-5-nitrobenzylidene amino)-5-methyl isoxazole [HNBMI] which were obtained by the condensation of 3-amino-5-methyl isoxazole with substituted salicylaldehydes have been synthesized. Schiff bases and their complexes have been characterized on the basis of elemental analysis, magnetic moments, molar conductivity, thermal analysis and spectral (IR, UV, NMR and Mass) studies. The spectral data show that these ligands act in a monovalent bidentate fashion, co-ordinating through phenolic oxygen and azomethine nitrogen atoms. Chelates of Co(II), Ni(II) appear to be octahedral and Cu(II) appears to be distorted octahedral. To investigate the relationship between formation constants of binary complexes and antimicrobial activity, the dissociation constants of Schiff bases and stability constants of their binary metal complexes have been determined potentiometrically in aqueous solution at 30+/-1 degrees C and at 0.1 M KNO3 ionic strength and discussed. Antimicrobial activities of the Schiff bases and their complexes were screened. The structure-activity correlation in Schiff bases and their metal(II) complexes are discussed, based on the effect of their stability constants. It is observed that the activity enhances upon complexation and the order of activity is in accordance with stability order of metal ions.     

羟甲基环氧树脂的“邻位效应”的探讨

邻位羟甲基环氧树脂由于在其缩水甘油醚基的邻位引入了羟甲基而使环氧基反应活性提高。本文合成了邻位和对位羟甲基苯基缩水甘油醚作为模型化合物,通过差热分析和红外光谱研究了它们与4,4′-二氨基二苯甲烷的反应,并对Schwarzer提出的“邻位效应”进行了探讨。     

Iron(III) Schiff base complexes with asymmetric tetradentate ligands: synthesis,spectroscopy, and antimicrobial properties

The synthesis and characterization is reported of four iron(III) complexes of general formula [Fe(pythsalX)(H₂O)₂]Cl₂, derived from the NSNO-donor tetradentate Schiff base ligands pythsalHX ([5-X-N-(2-pyridylethylsulfanylethyl)salicylideneimine] (X = OMe, N₂Ph, I, NO₂). The complexes were characterized by physico-chemical and spectroscopic methods. The thermal stabilities of both the free Schiff bases and their complexes were studied by differential scanning calorimetry and thermogravimetric analyses. The spectroscopic data suggest that the Schiff base ligands coordinate through deprotonated phenolic oxygen, imine, and pyridine-type nitrogens and the thioether sulfur atoms to give an octahedral geometry around the iron(III) atom in all these complexes. The free Schiff bases and their complexes have been screened for antimicrobial activities and the results show that the free Schiff bases are more potent antibacterials than the complexes.     

Solvent-free synthesis of dihydroxy dithiacrown ethers

The solvent-free reaction of oligoethylene glycol diglycidyl ethers with dimercaptoethane in the presence of benzyltrimethylammonium hydroxide (Triton B) gave, via regiospecific epoxide opening reactions, dihydroxy dithiacrown ethers in excellent yields and in short reaction times.     

Schiff碱型双冠醚的合成及性质

用脂链或芳环桥联两个苯并—15—冠—5单元的双冠醚报道较多,而桥联苯并-18-冠-6或苯并-12-冠-4单元的双冠醚报道较少。本文报道以α,ω-二卤代烷或二(对甲苯磺酸)二甘醇酯与邻羟基苯甲醛反应,制成相应的二醛化合物1_(α-∫)后使它们分别与4′-氨基苯并-18-冠-6或4′-氨基苯并-12-冠-4反应,得到脂芳混合桥联的schiff碱型双冠醚2_(b-∫)或3_(?)。     

Polymeric Schiff Bases. III. Some Prototype Exchange Reactions of Schiff Bases

The amine moiety in Schiff bases can be exchanged quantitatively by another amine to yield new Schiff bases if the volatility of the replacing amine is lower than the derived amine, thereby allowing the latter to distilled from the reaction mass. This amine exchange was shown to be quantitative also for diamines and di-Schiff bases. Similarly, quantitative conversions were found for aldehydes and acetal exchanges with Schiff bases for both monofunctional and difunctional reactants. The bis exchange, involving two complementary Schiff bases, was quantitative also when the reactants were so selected that one of the new derived Schiff bases could be removed by distillation. The bis exchange was demonstrated with mono and di-Schiff bases.

Mechanisms are suggested for these Schiff base exchange reactions: attempts to isolate the proposed intermediates physically were unsuccessful; however spectroscopic evidence indicates the formation of intermediate compounds.

The Schiff base exchanges involving polyfunctional reactants are of interest in the synthesis of polymers.     

Quantification of derivatives of bisphenol A diglycidyl ether (BADGE) and novolac glycidyl ether (NOGE) migrated from can coatings into tuna by HPLC/fluorescence and MS detection

A reversed phase high performance liquid chromatographic method combined with fluorescence and mass spectrometric detection in series is presented for the separation and quantification of bisphenol A diglycidyl ether (BADGE) and novolac glycidyl ether (NOGE) derivatives in extracts from food can coatings, tuna and oil. Fifteen samples of tuna cans bought in four European countries were investigated. Atmospheric pressure chemical ionization mass spectrometry in the positive ion mode (APCI(+)-MS) allowed to tentatively identify BADGE and NOGE related compounds originating from reactions of the glycidyl ethers with bisphenols, phenol, butanol, water and hydrochloric acid. Quantification was based on the external standard method and fluorescence detection. Mass fractions up to 3.7 μg/g were found for hydrochlorination products of bisphenol F diglycidyl ether (BFDGE + 2HCl) in tuna. Furthermore, total migration quantities of phenolic ether compounds were estimated. The highest values found were 20 μg/g in tuna and 43 μg/g in the oil phase. Received: 16 October 2000 / Accepted: 17 November 2000     

Spectral,magnetic, biological,and thermal studies of metal(II) complexes of some unsymmetrical Schiff bases

New nickel(II) and copper(II) complexes with unsymmetrical Schiff bases derived from aromatic 2-hydroxy aldehydes were synthesized and characterized by elemental analyses, melting points, ¹H-NMR, magnetic susceptibility, thermogravimetric analysis, differential scanning calorimetry (DSC), infrared (IR), and electronic spectral measurements. Comparison of IR spectra of the Schiff bases and their metal complexes indicated that the Schiff bases are tetradentate, coordinated via the two azomethine nitrogens and the two phenolic oxygens. Magnetic moments and electronic spectral data confirm square-planar geometry for the complexes. Thermal studies reveal a general decomposition pattern, whereby the complexes decomposed partially in a single step due to loss of part of the organic moiety. A single endothermic profile, corresponding to melting point, was observed from the DSC of all complexes, except those whose ligand contained the nitro group, which decomposed exothermally without melting. The Schiff bases and their complexes were screened in vitro against 10 human pathogenic bacteria. The metal(II) complexes exhibited higher antibacterial activity than their corresponding Schiff bases.     

Potentiometric Studies of Copper(II) Complexes of Some Substituted Benzylidene-2-Hydroxyanilines in Dioxane–Water Media

The formation and protonation constants of 17 Schiff bases-derived 2-hydroxyaniline with some substituted benzaldehydes, and the stability constants of Cu(II) complexes of these Schiff bases, have been determined potentiometrically in 20, 40, and 60% dioxane–water media. The data from the potentiometric titrations were evaluated with the BEST computer program. For all Schiff bases studied, it was observed that the log K_OH values related to the protonation equilibria of the phenolic oxygen are increased, and the log K_NH values related to the protonation equilibria of the azomethine nitrogen are decreased, as the dioxane content is increased. The variation of these constants is discussed on the basis of specific solute–solvent interactions and structural changes of Schiff bases from water to the dioxane–water media. Also, titrimetric-pH investigation of substituted benzilidene-2-hydroxyaniline systems has revealed the formation of stable mono-Schiff base complexes with the metal ion Cu(II).     

Coordination compounds of hydrazine derivatives with transition metals,part XVIII. Cobalt(II) and cobalt(III) chelates with schiff bases derived from hydrazine-S-methyldithiocarboxylate and thiosemicarbazide

Summary The reactions of aldehydic and ketonic Schiff bases derived from hydrazine-S-methyl dithiocarboxylate and thiosemicar-bazide with cobalt(II) acetate were investigated. Octahedral tris ligand cobalt(III) chelates were formed with aldehydic Schiff bases whereas tetrahedral bis ligand cobalt (II) chelates were isolated with ketonic Schiff bases.N-isopropylidene hydrazine-S-methyldithiocarboxylate, however, gave both octahedral tris cobalt(III) and tetrahedral bis cobalt(II) chelates. These results are interpreted in terms of the steric requirements of the Schiff base used.     

N,N'-dipyridoxyl Schiff bases: synthesis, experimental and theoretical characterization

Three N,N'-dipyridoxyl Schiff bases (L1, L2 and L3) have been newly synthesized and characterized by IR, (1)H NMR, mass spectrometry and elemental analysis. Their optimized geometries together with the theoretical assignment of the vibrational frequencies and the (1)H NMR chemical shifts of them have been computed by using density functional theory (DFT) method. In the optimized structures of the Schiff bases, two pyridine rings are not in a same plane; however the substitutions are essentially in the same plane with the pyridine rings. Also, the benzene ring(s) in the bridge region is (are) not in the same plane with the pyridine rings and azomethine moieties. In all the species, engagement in intramolecular-hydrogen bonds causes to weakness of the phenolic O-H bonds. Consistency between the theoretical results and experimental evidence confirms suitability of the optimized geometries for the synthesized Schiff bases.     

Antioxidant properties of phenolic Schiff bases: structure–activity relationship and mechanism of action

Phenolic Schiff bases are known for their diverse biological activities and ability to scavenge free radicals. To elucidate (1) the structure–antioxidant activity relationship of a series of thirty synthetic derivatives of 2-methoxybezohydrazide phenolic Schiff bases and (2) to determine the major mechanism involved in free radical scavenging, we used density functional theory calculations (B3P86/6-31+(d,p)) within polarizable continuum model. The results showed the importance of the bond dissociation enthalpies (BDEs) related to the first and second (BDE_d) hydrogen atom transfer (intrinsic parameters) for rationalizing the antioxidant activity. In addition to the number of OH groups, the presence of a bromine substituent plays an interesting role in modulating the antioxidant activity. Theoretical thermodynamic and kinetic studies demonstrated that the free radical scavenging by these Schiff bases mainly proceeds through proton-coupled electron transfer rather than sequential proton loss electron transfer, the latter mechanism being only feasible at relatively high pH.     

三种水杨醛类席夫碱的合成与性质研究

以取代水杨醛和3-氨基噻吩为原料合成了三种水杨醛类席夫碱,探讨了水杨醛结构中酚羟基对位取代基结构变化对于该席夫碱探针的激发态内质子转移过程、pH响应和金属离子响应的影响。研究结果表明,改变取代基团的推、吸电子能力,可调节酚氧负离子对活泼氢的束缚能力,进而影响这些席夫碱分子的激发态内质子转移性能。同时,酚氧负离子的电荷密度也决定了其与阳离子的配位能力,从而表现出不同结构的席夫碱对金属离子的选择性和灵敏性差异。     

Liquid-crystalline quinoline derivatives

A number of novel liquid crystals have been synthesized. 2-Phenylquinolines with alkyl or alkoxyl substituents in positions 6 and 4' show a texture typical of nematic mesophases and are characterized by a greater thermal stability than Schiff bases bearing the same substituents. The possibility of lowering the melting temperatures by means of eutectic mixtures is discussed.     

Synthesis, characterization, tautomerism and theoretical study of some new Schiff base derivatives

New Schiff base derivatives were prepared by the condensation of 5-chloro and 5-bromo salicylaldehyde with bis(o-aminophenol)ethers. Five bis(o-nitrophenol)ether compounds were synthesized using some ditosylate, 1,3-dibromopropane and 1,4-dibromobuthane with o-nitrophenol. These compounds were reduced to bis(o-aminophenol)ethers. The products have been characterized by elemental analysis, FTIR, 1H, 13C NMR, HETCOR and HMBC spectroscopic techniques. The tautomerisms of all of the Schiff bases compounds were determined in DMSO, CHCl3, C2H5OH and C6H12 solvents and in both acidic and basic media using the UV-vis spectrophotometric method. The heat of formation (ΔHf), enthalpy (ΔH), entropy (ΔS), Gibbs free energy (ΔGf and ΔG), stable isomers, conformations and tautomers of the synthesized compounds are calculated using the MOPAC2009 (PM6) program.     

Synthesis and characterization of nitro-Schiff bases derived from 5-nitro-salicylaldehyde and various diamines and their complexes of Co(II)

Some neutral tetradentate N₂O₂ type complexes of Co(II) have been synthesized using Schiff bases formed by condensation of 5-nitro-salicylaldehyde with various diamines in alcohol. The nature of the ligands and complexes was established by spectroscopic techniques. The Schiff bases are bivalent anions with tetradentate ONNO donors derived from phenolic oxygen and azomethine nitrogen. IR and UV-Vis spectral data suggest that all the complexes are square-planar.