Synthesis,tautomeric stability,spectroscopy and computational study of a potential molecular switch of (Z)-4-(phenylamino)pent-3-en-2-one

The (Z)-4-(phenylamino) pent-3-en-2-one (PAPO) was synthesised applying carbon-based solid acid and described by experimental techniques. Calculated results reveal that its keto-amine form is more stable than its enol-imine form. A relaxed potential energy surface scan has been accomplished based on the optimised geometry of NH tautomeric form to depict the potential energy barrier related to intramolecular proton transfer. The spectroscopic results and theoretical calculations demonstrate that the intramolecular hydrogen bonding strength of PAPO is stronger than that in 4-amino-3-penten-2-one)APO(. In addition, molecular electrostatic potential, total and partial density of stats (TDOS, PDOS) and non-linear optical properties of the compound were studied using same theoretical calculations. Our calculations show that the title molecule has the potential to be used as molecular switch.     

Study of Enol-Keto Tautomerism of N-(2-Hydroxy-1-Naphthylidene)anils

The enol-keto tautomerism of N-(2-hydroxy-1-naphthylidene)anilines was studied. In response to the action of salts (e.g. CaCl₂), in ethanolic solution the equilibrium is shifted extensively in the direction of the keto form; this allows determination of the concentration of the keto form and of the equilibrium constant of the process. In accordance with the Hammett equation, the equilibrium constant varies as a function of the constants a of the substituents on the aniline ring.     

Synthesis and Spectroscopic Studies of Some New Polyether Ligands of the Schiff Base Type

Abstract

New polyether ligands of Schiff base type (3–13) were synthesized from the reaction of diethylene glycol bis(2‐aminophenyl)ether and triethylene glycol bis(2‐aminophenyl)ether with salicylaldehyde, 5‐methoxysalicylaldehyde, 5‐bromosalicylaldehyde, 5‐nitro salicylaldehyde, and 2‐hydroxy‐1‐naphthaldehyde. The products were characterized by elemental analysis, IR, ¹H, ¹³C NMR, and UV‐VIS techniques. The UV‐VIS spectra of those Schiff bases with an OH group in the ortho position to the imino group were studied in polar and nonpolar solvents in acidic and basic media. The compounds are in tautomeric equilibrium (enol‐imine, O–H · N?keto‐amine, O · H–N forms) in solvents, acidic chloroform, and benzene solutions and basic DMSO, chloroform, and benzene solutions. These tautomers were not observed in polar and non‐polar solvents and in basic solutions of DMSO, chloroform, and benzene for the Schiff bases 5–10. Tautomer proportions, which were obtained from ¹H NMR and UV‐VIS data in DMSO, were compared for compounds 3, 4, 11, and 12.     

Influence of oxygen in lower homologues of Schiff-base compounds: a comparative study

The lower homologues (n/m?≤?5) of Schiff base mesogenic compounds, obtained by placing the electro-negative oxygen atom at the bridging site to the essential rigid core, are synthesized, and investigated by polarized-light thermal microscopy and differential scanning calorimetry. The influence of oxygen atoms, to the extent of increase of thermal range, depression in melting temperatures, elevation of clearing temperatures and quenching of liquid crystalline phases, is presented as a function of contributions to the longitudinal dipole moment of the molecule.     

一种新型希夫碱锌配合物的合成及光谱学性质

合成了一种希夫碱有机金属配合物2-羟基-1-萘甲醛缩邻苯二胺合锌(ZnL)。通过质谱、元素分析、红外光谱、热重分析对其结构进行了表征;利用紫外-可见光吸收光谱、激发和发射光谱研究了该配合物的光物理性能。结果表明:ZnL的热分解温度为433.2℃,具有很好的热稳定性;在DMF溶液体系中,配合物ZnL的紫外吸收带位于250~500nm,荧光激发带位于343~493nm,在紫外光的激发下发射峰在626nm处,为橙红色光,最佳激发波长为470nm,禁带宽度2.32eV。

     

Infra-Red Study of Tautomerism in Some Schiff Bases.

Infra-Red spectra of a series of substituted salicylaldehyde and 2-hydroxy-naphthaldehyde Schiff bases were used to investigate enol-keto tautomeric equilibrium. Two model compounds, namely, salicylidinaniline and naphthylidinequinolineamine Schiff bases were used to represent the enol and keto forms, respectively. From the IR spectra of the model compounds it was possible to assign the IR absorption for the C=O and the C=N groups in both the keto and the enol form. It was also possible to assign other absorptions which were either specific to the keto or the enol forms. Specific pattern were observed for all the studied compounds.     

Cu(Ⅱ)、Zn(Ⅱ)Schiff碱配合物的光谱分析及其对超氧离子的抑制作用

以水杨醛为原料,通过与混酸作用制备了5-硝基水杨醛,将其与盐酸氨基脲缩合制备出一种Schiff碱配体, 用Cu(Ⅱ)和Zn(Ⅱ)分别与配体在70 ℃左右的恒温水浴中反应1.5 h,合成出了新型Schiff碱配合物。用元素分析、红外光谱、紫外光谱、差热热重、摩尔电导率、核磁共振等分析方法对化合物进行表征和测试,采用蛋氨酸光照法测定了配合物对超氧离子的催化歧化作用。结果表明,该Schiff碱配体及其配合物,组成确定,热力学稳定性高,在核黄素光照产生-₂的体系中,配合物都表现出良好的生物活性,对超氧离子有很强的催化歧化作用,尤其是双配体铜配合物活性最强,对人红细胞内血红蛋白具有一定的保护作用。     

糠醛缩壳寡糖席夫碱及Cu（Ⅱ）配合物与DNA之间的作用机制

以糠醛和壳寡糖反应生成的席夫碱,与不同摩尔比的Cu²⁺配位合成配合物FCOS-Cu11、FCOS-Cu13和FCOS-Cu31,并研究配合物与DNA之间的作用机制。采用循环伏安、紫外-可见吸收光谱、粘度和DNA熔点测定的方法,分别研究了席夫碱及配合物与DNA之间的作用机制。合成的3种配合物具有电化学活性。加入DNA后,配合物的氧化峰电流减小,峰电位微弱移动。配合物的吸收峰强度减色显著,同时伴有峰位红移现象。配合物加入后,DNA的相对粘度和熔点呈增大趋势。结果表明,席夫碱及配合物与DNA之间存在嵌插结合,且3种配合物中的Cu²⁺含量与DNA的嵌插作用强度有关,结合强度依次为FCOS-Cu11>FCOS-Cu13>FCOS-Cu31。

     

光致变色Schiff碱N,N’-双(水杨醛缩)-1,2-环己二胺的荧光光谱

用稳态和时间分辨荧光光谱研究了Ｎ,Ｎ’ 双水杨醛缩 １,２ 环己二胺（Ｎ,Ｎ’ ｂｉｓ（ｓａｌｉ ｃｙｌｉｄｅｎｅ） １,２ ｃｙｃｌｏｈｅｘａｎｅｄｉａｍｉｎｅ,ＢＳＣ）在固态和四氯化碳、氯仿溶液中的光致变色行为。发现经过光照,ＢＳＣ的荧光光谱发生了明显、快速的改变,并且光致变色过程可重复进行。     

Mass Spectral Study of Tauotomerism in Some Schiff Bases

Mass spectra of a series of substituted salicylaldehyde and 2-hydroxy-naphthaldehyde Schiff bases were used to investigate enol-keto tautoraeric equilibrium. Two model compounds, namely, salicylidinaniline and naphthylidinequinolineamine Schiff bases were used to represent the enol and keto forms, respectively. Mass spectral measurements reveal the fragmentation pattern in all compounds studied. Only naphthylidinequinoline amine Schiff base show a different fragmentation pattern compared to the other Schiff bases in the series which give an evidence for its suggested keto structure.     

咔唑-硫脲席夫碱荧光探针对Hg~(2+)和Ag~+的可视化识别

以3-溴代-N-丁基咔唑和4-苯基-3-氨基硫脲为原料,合成了一种新型含咔唑基的硫脲席夫碱L,使用紫外-可见光谱、荧光光谱、核磁氢谱以及质谱等对其成分结构、离子识别性能、识别模式进行了研究。结果表明:L对Hg2+和Ag+具有快速响应的可视化选择性识别。当Hg2+或Ag+加入后,L溶液的颜色由无色立刻变为黄色;同时,L溶液中加入Hg2+和Ag+后,荧光光谱有不同变化,且其他离子的存在并不干扰L对Hg2+和Ag+的选择性识别。研究还发现,L对Hg2+和Ag+的荧光识别模式不同:加入Ag+后,L与Ag+生成了配合物,发生荧光猝灭;加入Hg2+后,L先与Hg2+络合发生荧光猝灭,然后脱去Hg S。     

The effect of some Schiff bases on the corrosion of aluminum in hydrochloric acid solution

The inhibition effect of Schiff bases benzylidene-(2-methoxy-phenyl)-amine (A), (2-methoxy-phenyl)-(4-methyl-benzylidene)-amine (B), (4-chloro-benzylidene)-(2-methoxy-phenyl)-amine (C) and (4-nitro-bezylidene)-(2-methoxy-phenyl)-amine (D) on the corrosion of aluminum in 1 M HCl has been studied by polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurements. It has been found that all the studied Schiff bases are excellent inhibitors. Maximum inhibition was obtained for 0.01 M Schiff base A. Results show that the inhibition efficiency increases with decreasing in temperature and increasing in concentration of Schiff base. Polarization curves reveal that the used inhibitors are mixed type inhibitors. The surface adsorption of the Schiff bases leads to a decrease of double layer capacitance as well as an increase of polarization resistance. The inhibitor performance depends strongly on the type of function groups substituted on benzene ring. The adsorption of used compounds on the aluminum surface obeys a Langmuir isotherm and has a physical mechanism. Thermodynamic parameters for both dissolution and adsorption processes were determined. The quantum chemical study of the corrosion inhibition efficiency of the Schiff bases on Al in molar HCl was carried out.