分光光度法定量测定柠檬酸及其盐的含量

酸性介质中,柠檬酸(或盐)与Fe3+形成的黄色络合物在光照条件下发生光致变色现象,生成紫红色络合物,采用分光光度法可定量测定柠檬酸及其盐的含量.在冰水浴中,日光照射20 min,阴凉处静置30 min,检测波长为490nm.线性范围为(0～300)mg/L,相对标准偏差(RSD)为0.46％(n=6),检测限为3.46...     

Photochromism of dihydroindolizines. Part 12: synthesis and photochromism of novel π-conjugated rigid dihydroindolizines as potential molecular electronic devices

Novel carbon-rich photochromic dihydroindolizine DHI derivatives and new spirocyclopropenes have been synthesized. Three alternative synthetic pathways for the synthesis of DHI 10 have been established. Different Sonogashira-mediated coupling reactions have been applied to optimize the reaction conditions and to obtain the best yields. Palladium-mediated Sonogashira coupling of DHIs with 4-(thioacetyl)iodobenzene 13 and iodobenzene 17 yielded coupling products, which have potential applications in molecular electronics. Irradiation of photochromic DHIs 10a-f, 12a-f, 14a-f, 16a-f and 18a-f with polychromatic light leads to betaines 9a-f, 13a-f, 15a-f, 17a-f and 19a-f. The coloured betaine forms are obvious in CH₂Cl₂ solution with concentration of 1×10⁻⁵ mol/L at room temperature because of their slower 1,5-electrocyclization. All the absorption maxima of the coloured betaines were found to be in the visible region and lie between 524 (betaine 9a) and 639 nm (betaine 15f). The kinetics of the thermal 1,5-electrocyclization was studied using multichannel UV-vis spectrophotometry. The kinetic measurements showed that the half-lives of the coloured betaines are in the second domain and lie between 112 and 1379 s. A highly pronounced increase in the half-lives of betaines bearing dimethyl substituted pyridazine compared with non-substituted pyridazine betaines was monitored. A large increase in the photostability of both DHIs and betaines under investigation compared with the standard DHI was observed. The charged zwitterionic betaine structures were stabilized by increasing the solvent polarity due to the electrostatic interactions between them. The tuning of the absorption maxima and the kinetic properties by changing the substitution in the fluorene part (region A) and pyridazine part (region C) will help these compounds to find their applications.     

Highly stable and fluorescent switching spirooxazines

Two novel photochromic spirooxazines, SO-NA1 and SO-NA2, containing a naphthalimide unit were synthesized. The imide group of naphthalimide unit is incorporated at the naphthoxazine fragment, thus giving strong electron-withdrawing effect favoring the long-lived merocyanine (MC) in the dark giving good colorability in solution. Remarkably, their open merocyanine (MC) forms exhibit significantly long lifetimes, almost three magnitudes longer than that of unsubstituted spironaphthoxazine (1). Moreover, the fluorescence of naphthalimide unit can be switched on and off by photoinduced conversion between the open and closed forms.     

SYNTHESES OF PHOTOCHROMIC PIGMENTS

Photochromism is a phenomenon that a compound undergoes a reversible color change with the change of the wavelength of the irradiating light. Many photochromic compounds have been used in textiles as photochromic pigments.In this paper, some special techniques are used to prepare a photochromic compound of spirooxazines with an improved yield. Another photochromic spirooxazine with a sulfonate group which is soluble in water is also successfully synthesized. Tests are also conducted to find that they both display good photochromism in proper states.     

A highly selective fluorescent probe for Sn based on a new photochromic diarylethene with a phenol-containing Schiff base unit

A novel diarylethene with a phenol-containing Schiff base unit was successfully synthesized and its multi-responsive photoswitching property was investigated by the stimulation of base/acid and light. The diarylethene showed not only normal photochromism by photoirradiation, but also abnormal photochromism by base and light stimuli. By the stimulation of sodium hydroxide, the absorption maximum of its open-ring isomer showed extraordinarily large redshift of 60 nm, accompanied with a notable color change from colorless to yellow. Subsequent irradiation with 297 nm light further caused a dramatic change in its structure transformation from the deprotonated open-ring isomer to the original closed-ring isomer. Similarly, its deprotonated closed-ring isomer returned to its original open-ring isomer upon irradiation with appropriate visible light. Its deprotonated forms could be restored by the stimulation of hydrochloric acid. Moreover, the diarylethene could be served as a fluorescence probe for recognition of Sn²⁺ with high selectivity.     

双光子辐照下的螺吡喃聚合物薄膜偏振全息光栅记录研究

螺吡喃聚合物薄膜在短波辐照后的曝光灵敏度和偏振敏感性均得到显著提升.基于这一特性,在线偏振的蓝紫光(405nm)伴随下,用两束耦合的绿光(532nm)以s-p的记录模式在螺吡喃掺杂的PMMA聚合物薄膜上构建全息光栅,并通过低功率红光(632.8nm)进行探测.在405nm和532nm双光子共同作用下,衍射效率动力学特性强烈依赖于辅助光功率.研究发现,405nm激光辐照产生了两种作用:一方面为记录光提供了可取向的部花青分子;另一方面,扰乱了532nm激光形成的折射率光栅并降低了部花青分子的转化活性.考虑到光栅随机光场区的部花青分子聚集体的存在,本文建立了包含衍射效率与各分子光响应速率关系的理论模型.实验数据与拟合结果精准吻合,有效地解释了偏振全息记录中螺吡喃与部花青分子相互转化的微观机制.     

A sensitive sensor for Cu(II) based on a novel diarylethene with a bipyridyl moiety

A novel diarylethene with a bipyridyl unit has been designed and synthesized for the first time. Its photochromic behaviors could be modulated by protonation and coordination with Cu(II). The absorption maximum of the closed-ring isomer shifted from 569 to 666 nm when trifluoroacetic acid was added. Furthermore, the closed-ring isomer behaved as a sensitive colorimetric sensor, exhibiting an open-ring reaction upon exposure to Cu(II). Its high selectivity toward Cu(II) over other competitive species makes the ‘naked-eye’ detection of Cu(II) possible.     

Synthesis of 1′,3,3′,4-tetrahydrospiro[chromene-2,2′-indoles] as a new class of ultrafast light-driven molecular switch

A new class of ultrafast light-driven molecular switch has been designed and synthesized. The reaction of 1-substituted 2-methylidene-3,3-dimethyl-2,3-dihydro-1H-indoles with 2-chloromethyl-4-nitrophenol afforded 1′,3,3′,4-tetrahydrospiro[chromene-2,2′-indoles], following a basic workup. The spectroscopic properties and nanosecond-resolved photoinduced dynamics of five compounds in the 1′,3,3′,4-tetrahydrospiro[chromene-2,2′-indole] family were investigated.     

A simple strategy for constructing acylhydrazone photochromic system with visible color/emission change and its application in photo-patterning

As a potential photochromic system, acylhydrazones exhibit many outstanding advantages including low cost, simple synthesis and high modifiability compared with some classic photochromic systems. However, the absorption wavelengths of acylhydrazones usually locate in ultraviolet region, which makes the band separation between the absorbance maxima of its irradiated and unirradiated forms cannot be observed by naked eyes and greatly limits their practical applications. In this work, a simple strategy for constructing acylhydrazone photochromic system with visible color/emission change is provided. Rhodamine 6G hydrazine-2-aldehyde-pyridine Schiff base (compound 3) is designed and synthesized by combining acylhydrazone with Rhodamine 6G structure. The introduction of Rhodamine 6G moiety to 3 not only makes it remain all the advantages of acylhydrazone photochromic system but also exhibits visible photo-induced color/emission changes both in solution and in a solid matrix. Moreover, 3 exhibits reversible photochromic property with good fatigue resistance, which makes it an excellent candidate for photo-patterning.     

Synthesis and photoreaction mechanism of a novel bifunctional photochromic compound

New functionalized spiroxazine containing azo group has been prepared and its photochromic mechanism has been investigated by laser induced time-resolved techniques.