光致变色水杨醛缩胺类Schiff碱的荧光性质

测字了双杨醛缩邻苯二胺（１）,缩对苯二胺（２）、缩１,２－环已二胺（３）、缩乙二胺（４）、缩１,６－已二胺（５）中和水杨醛缩a－苯乙胺（６）在溶液中以及固态时的荧光光谱,研究了Ｓchiff减１,３,４,５和６在固态和溶液中的光致变色行为。     

Photochromic fluorescence switching from diarylethenes and its applications

The review describes the photochromic and fluorescent characteristics of various diarylethene (DAET) derivatives, and presents recent research into their applications. This comprises a discussion of the optical characteristics of some DAET-based molecules exhibiting red, green, or blue (RGB) colors or fluorescence. Molecular calculations of the optical properties of DAET interpret intriguing experimental observations and predict photochemical or photophysical properties. In particular, stabilization of HOMO in the BTFOn (n = 1, 2, 3, 4) increases the energy difference between the HOMO and the LUMO, which leads to the blue-shift of absorption and emission bands as the number of oxygen attached to sulfur (n) increases. Various devices and application studies have been designed as photon-mode systems based on photochemical control of the fluorescence energy. The photochromic DAET materials have shown promise as optical data storage, switching devices, and biological applications such as the development of biomaterial sensors, analysis of biological dynamics, and live cell imaging.     

Photochemical behaviour of Schiff base liquid crystals based on isoxazole and isoxazoline ring. A kinetic approach

ABSTRACT

The kinetic study on the hydrolysis of Schiff bases (SBs) 1a-c and 2a-c induced by UV-vis was undertaken as a complementary study of the stability in solution and in bulk of the SBs. Solutions in chloroform were exposed to UV-vis and acquisition data occurred for 1a-c and for 2a-c in 21°C, 30 °C, 35°C and 40°C. Kinetic profile for 1a-c and 2a-c displayed the similar photochemical behaviour in that four temperature values. At 21°C, two kinetic regimes were observed where the decomposition of SBs is faster at the initial stage, with no linear plot of absorbance vs time, and after the kinetic profile obeyed a linear behaviour. A mathematical treatment of the experimental data was applied, which allowed associating the initial stage data with a second-order reaction, and the final stage of the hydrolysis with a first-order reaction. The mechanism of photochemical hydrolysis of SBs 1a and 2a was addressed. It was composed of three parts, the excitation, then the isomerisation and activation processes of tetrahedral intermediate and, the last process, a collapse of the intermediate to the yielded products of the hydrolysis aldehydes and amines which were detected by their UV-vis spectrum.     

Polarisation switching and molecular relaxation behaviour of anthraquinone dye-dispersed polymer-stabilised ferroelectric liquid crystal composites

Guest–host polymer-stabilised ferroelectric liquid crystal (GH-PSFLC) composite films have been prepared with dispersion of small concentration (0.1, 0.25 and 0.5 wt%) of anthraquinone blue dye in PSFLC host matrix via a polymerisation-induced phase separation (PIPS) process. The variation in alignment and size of twisted fibril has been observed in the optical textures of the guest–host composites with different wt/wt ratio of anthraquinone dye. The electrical and dielectric properties of PSFLC mixture and its guest–host derivatives are studied. Our results showed that an optimum amount of dye concentration (0.1 wt%) enhances the dielectric permittivity as well as the spontaneous polarisation of the GH-PSFLC material in the SmC* phase.     

含席夫碱基的螺噁嗪类光致变色化合物的合成及性质

设计合成了一系列含席夫碱基的螺噁嗪双功能光致变色材料4a~4d. 通过¹H NMR, ¹³C NMR, IR和HRMS对其结构进行了表征. 新化合物在几种有机溶剂中均表现出了良好的光致变色性. 研究了化合物在几种高分子膜中的光致变色性. 比较了化合物4b的开环体在两种不同溶剂, 即甲醇和二甲亚砜, 以及3种高分子介质, 即聚甲基丙烯酸甲酯(PMMA)、聚乙烯醇缩丁醛(PVB)和聚乙烯醇(PVA)中的消色速率. 研究了化合物在甲醇、二甲亚砜、PMMA及PVB中的消色过程动力学, 根据化合物在溶液中和高分子介质中开环体消色过程的差别, 推测了存在两种动力学解释的原因. 研究结果显示, 化合物4d在PMMA膜中的耐疲劳度良好.     

含席夫碱基的螺吡喃双功能光致变色材料的合成及性质

设计合成了一系列含席夫碱基的螺吡喃双功能光致变色材料4a~4n. 通过1H NMR, IR和HRMS对其结构进行了表征. 研究了化合物在几种溶剂和PMMA膜中的光致变色性质, 研究了化合物4a在甲醇中, 以及化合物4a和4f在高分子介质聚甲基丙烯酸甲酯(PMMA)中的消色过程. 结果表明, 化合物4e在PMMA膜中光照后呈现出与其它化合物不同的颜色, 为罕见的绿色. 化合物4a在二氯甲烷溶液中有良好的荧光性能. 所合成的新型含席夫碱基的螺吡喃双功能光致变色材料在甲醇、二氯甲烷和环己烷溶液中及在PMMA膜中均表现出良好的光致变色性质.     

Photochromic and reductive electrochemical switching of a dithiazolylethene with large redox modulation

A new dipyridylthiazolylethene (1a) and its dicationic analogue (2a), with two N-methylated pyridyl rings, have been synthesized and structurally characterized. Due to the N-methylation of the pyridyl rings, 2 a displays not only very different photochromic properties, but also undergoes a reductive ring-closing reaction to generate its closed-ring isomer 2b. Careful electrochemical studies coupled with EPR spectroscopy show that this reductive ring-closing reaction takes place when 2a is two-electron reduced. DFT calculations suggest that such a ground-state electrocyclization is driven by a very large stabilization of the reduced closed-ring isomer 2b relative to the reduced open-ring isomer 2a. In addition, 2b exhibits two successive and reversible one-electron reductions at half-wave potentials of 0.04 and -0.14 V versus SCE and a redox modulation as large as 1 V is achieved when passing from 2a to 2b.     

Thiocyanate-selective electrode based on cobalt(II) complexes of pyrazolone heterocyclic Schiff bases

A new solvent polymeric membrane electrode based on pyrazolone heterocyclic Schiff base complexes of Co(II) is described. It shows a preferential response towards thiocyanate over a range of 2.0 × 10^–6 to 1.0 × 10^–1 mol L^–1 with a slope of –60.2 ± 0.6 mV/dec. The selectivity sequence observed is thiocyanate > hydroxide > nitrite > iodide > perchlorate > citrate > bromide > fluoride > chloride > nitrate > acetate > borate > sulfate > phosphate. The selectivity behavior is discussed in view of axial coordination by uv/vis spectroscopy and the transfer process of thiocyanate across the membrane interface is investigated by the ac impedance technique. The electrode was successfully applied to the determination of thiocyanate in human urine as an indicator for distinguishing between smokers and non-smokers.     

Synthesis,characterisation and liquid crystalline properties of some Schiff base and cinnamate central linkages involving 1,3,5-trisubstituted pyrazolone ring system and their Cu(II) complexes

Two new mesogenic homologous series, each containing 1,3,5-trisubstituted pyrazolone derivatives, 4-n-alkoxyphenyl and Schiff base–cinnamate central linkages, have been synthesised to give 4-[(5-hydroxy-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-4-yl) methyleneamino] phenyl 3-(4-n-alkoxyphenyl)acrylate [Series-A] and 4-[(5-hydroxy-3-methyl-1-p-tolyl-4,5-dihydro-1H-pyrazol-4-yl)methyleneamino] phenyl 3-(4-n-alkoxyphenyl)acrylate [Series-B] and their Cu(II) complexes have also been synthesised. These compounds were characterised by elemental analysis, Fourier transform infrared (FT-IR), proton nuclear magnetic resonance (¹H NMR), carbon-13 NMR (¹³C NMR) and ultraviolet (UV)-visible and mass spectral studies. Their mesomorphic behaviour was studied by polarising optical microscope (POM) with a heating stage. POM data were compared with differential scanning calorimetry thermograms. In Series-A and -B, all compounds exhibit mesomorphism. Series-A compounds exhibit an enantiotropic nematic mesophase except propyl derivative, while a smectic A (SmA) mesophase is observed from the heptyl derivative and persists up to the last member of the homologous series. n-Heptyloxy derivative is monotropic for SmA phase. Series-B compounds also exhibit the enantiotropic nematic mesophase, while the SmA mesophase is observed from the heptyl derivative and persists up to the last member of the homologous series. n-Dodecyloxy derivative exhibits monotropic SmA and nematic mesophases. The mesomorphic properties of both series are compared with each other and the other structurally related compounds. The study reveals that cinnamate linkage containing liquid crystals have higher thermal stability compared to structurally related series containing chalcone linkage. In case of complex series, only one compound from each series gives nematic mesophase.     

Thiocyanate-selective electrode based on cobalt(II) complexes of pyrazolone heterocyclic Schiff bases

A new solvent polymeric membrane electrode based on pyrazolone heterocyclic Schiff base complexes of Co(II) is described. It shows a preferential response towards thiocyanate over a range of 2.0 × 10^–6 to 1.0 × 10^–1 mol L^–1 with a slope of –60.2 ± 0.6 mV/dec. The selectivity sequence observed is thiocyanate > hydroxide > nitrite > iodide > perchlorate > citrate > bromide > fluoride > chloride > nitrate > acetate > borate > sulfate > phosphate. The selectivity behavior is discussed in view of axial coordination by uv/vis spectroscopy and the transfer process of thiocyanate across the membrane interface is investigated by the ac impedance technique. The electrode was successfully applied to the determination of thiocyanate in human urine as an indicator for distinguishing between smokers and non-smokers. Received: 30 September 1997 / Revised: 9 December 1997 / Accepted: 13 December 1997     

Photochromic coumarin spiropyranes with switching of optical properties by lanthanide ions

Russian Chemical Bulletin - Coumarin spiropyrans with terminal carbohydrazide substituents were synthesized. UV irradiation of their solutions was found to initiate rearrangement into a deeply...     

Photochromic behaviour of ozonated and photoirradiated cellulose studied by fluorescence spectroscopy

Samples of ozonated pure cotton cellulose have been subjected to three extended periods of irradiation with monochromatic light at 350 nm, with intervening dark periods. The changes during the treatments were monitored using fluorescence spectroscopy. Photochromic behaviour, comprising a fairly rapid emission intensity decrease during irradiation and a slower recovery of the emission intensity in the dark at ambient temperature, was observed. Starting from the completion of the first irradiation/dark treatment the intervening dark reaction almost completely restored the situation prevailing before irradiation. The photochromism observed for a reference sample of cellulose not pretreated with ozone and for microcrystalline cellulose was similar but differed both in amplitude and in fluorescence recovery during the dark periods. The ozonated sample was also irradiated with the entire spectrum of a medium pressure Hg lamp. This treatment caused a strong increase in the emission intensity and a red-shift of the emission maximum. The changes caused by ozonation and irradiation were also studied by diffuse reflectance FT-IR and UV-visible reflectance spectroscopy.     

Synthesis,DNA binding,and antimicrobial studies of novel metal complexes containing a pyrazolone derivative Schiff base

A novel series of Co(II), Ni(II), Cu(II), Zn(II), and VO(IV) complexes has been synthesized from the Schiff base derived from 4-[(3,4-dimethoxybenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one and 1,2-diaminobenzene. Structural features were determined by analytical and spectral techniques. Binding of synthesized complexes with calf thymus DNA (CT DNA) was studied by spectroscopic methods and viscosity measurements. Experimental results indicate that the complexes are able to form adducts with DNA and to distort the double helix by changing the base stacking. Lower DNA affinity of the VO(IV) complex is caused by the change of coordination geometry by the vanadyl ion resulting in a somewhat unfavorable configuration for the DNA binding. Oxidative DNA cleavage activities of the complexes were studied with supercoiled (SC) pUC19 DNA using gel electrophoresis; the mechanism studies revealed that the hydroxyl radical is likely to be the reactive species responsible for the cleavage of pUC19 DNA by the synthesized complexes. The in vitro antimicrobial screening effects of the investigated compounds were monitored by the disc diffusion method. The synthesized Schiff base complexes exhibit higher antimicrobial activity than the respective free Schiff base.     

Role of Knoevenagel condensate pyrazolone derivative Schiff base ligated transition metal complexes in biological assay and cytotoxic efficacy

A new bioessential Knoevenagel condensate Schiff base ligand (L) was synthesized by the reaction of 3‐(4‐hydroxy‐3‐methoxybenzyl)pentane‐2,4‐dione and 4‐aminoantipyrine. The ligand forms monomeric divalent transition metal complexes ( 1 – 4 ) which were characterized using spectral and analytical data. All these complexes have the general formula [ML]Cl₂, where M = Co(II), Ni(II), Cu(II) and Zn(II). They are electrolytic in nature and adopt square planar geometry. The binding propensity of these complexes with calf thymus DNA was investigated using absorption spectrophotometric titration, cyclic voltammetry and viscosity measurements. The binding constant values imply that the complexes bind with DNA via intercalation mode. The in vitro antibacterial and antifungal activities reveal that the complexes have good antimicrobial efficacy against a set of pathogens. The nucleolytic cleavage activity of these complexes on pUC18 DNA was investigated using agarose gel electrophoresis. Also, the in vitro cytotoxicity of the synthesized complexes against a panel of human tumour cell lines (MCF‐7 and HeLa) and normal cell lines (NHDF and HEK) was assayed using the MTT method. Interestingly, complex 1 exhibits more potent anticancer activity than cisplatin and other complexes.     

Photochromic switching of excited-state intramolecular proton-transfer (ESIPT) fluorescence: a unique route to high-contrast memory switching and nondestructive readout

Aiming at the high-contrast photochromic switching of fluorescence emission and its perfect nondestructive readout, a polymer film highly loaded with a specific photochromic compound, 1,2-bis(2'-methyl-5'-phenyl-3'-thienyl)perfluorocyclopentene (BP-BTE), and an excited-state intramolecular proton-transfer (ESIPT)-active compound, 2,5-bis(5'-tert-butyl-benzooxazol-2'-yl)hydroquinone (DHBO), was employed in this work. The special class of photochrome, BP-BTE, has negligible absorbance at 415 nm both in the open form and in the 365 nm photostationary state (PSS), and the ESIPT fluorophore, DHBO, emits large Stokes' shifted (175 nm; lambda(max)(abs) = 415 nm, lambda(max)(em) = 590 nm) and enhanced fluorescence (Phi(F)(powder) = 10%, Phi(F)(soln) = 2%). Bistability, high-contrast switching (on/off fluorescence switching ratio >290), nondestructive readout (over 125000 shots), and erasability were all together accomplished in this novel recording medium.     

Formation of enamine Schiff bases by ring cleavage of pyridine

On treatment with diphenyldichloromethane or anisal chloride in the presence of acetone and aqueous sodium hydroxide, pyridine undergoes condensation and ring cleavage to yield the enamine Schiff bases 1,1-diphenyl-2-azadeca-1,3Z,5Z,7E-tetraen-9-one (1) and 1-(4-methoxyphenyl)-2-azadeca-1E,3Z,5Z,7E-tetraen-9-one (7). The reaction proceeds through attack of acetonyl carbanion on the initially formed bis-pyridinium salt, followed by ring scission with elimination of one equivalent of pyridine. The structure and stereochemistry of the 2-azatetraene (1) was confirmed by X-ray crystallography.     

Synthesis and characterization of Ni(II) complexes of O,N-donor Schiff bases derived from acyl pyrazolone analogues

Two bidentate Schiff bases, 5-methyl-2-p-tolyl-4-(1-p-tolylimino-propyl)-2H-pyrazol-3-ol (L1) and 2-(3-chloro-phenyl)-5-methyl-4-(1-p-tolylimino-propyl)-2H-pyrazol-3-ol (L2), were synthesized by condensation of 4-acyl pyrazolones with p-toluidine in ethanol. These ligands have been characterized by elemental analysis, infrared (IR), ¹H NMR, and mass spectra. A single crystal molecular structure of ligand L2 was also solved. Nickel(II) complexes of these ligands with general formula [ML₂?·?2H₂O] have been prepared by the interaction of aqueous solution of Ni-acetate with ethanolic solution of the appropriate ligand. The complexes were separated, analyzed, and their structures were elucidated on the basis of elemental analysis, Ni(II) determination, IR, UV-Vis, conductance, mass, and TGA-DTA data. Octahedral structure was proposed for the synthesized complexes.     

含席夫碱基团的光致变色螺吡喃化合物的光谱性能和与DNA作用研究

本文合成6种带有席夫碱基团的螺吡喃光致变色化合物,并利用电子吸收光谱、荧光光谱研究了它们的光谱性质以及与DNA的相互作用,考察了不同基团对其作用的影响,对同一化合物研究了在不同pH值、不同离子强度条件下的作用情况,初步探讨了它们与DNA的作用方式.