DMABN测定含溴化钠或正丁醇水溶液中表面活性剂的临界胶团浓度

以对二甲氨基苯甲腈(DMABN)为探针, 测定它在含NaBr或n-C4H9OH的表面活性剂十二烷基三甲基溴化铵(C12TABr)、季铵盐Gemini表面活性剂C12-3-C12·2Br和十二烷基硫酸钠(SDS)水溶液中的第二重荧光对应的强度(Ia)和特征波长(λa)对表面活性剂浓度(c)曲线. 由Ia-c曲线的转折点或λa-c曲线对应的一阶导数极小点可以获得临界胶团浓度(cmc), 扩展了DMABN探针测定表面活性剂cmc的适用性.     

分子内扭转电荷转移探针DMABN测定表面活性剂水溶液的临界胶团浓度

以对二甲氨基苯甲腈(DMABN)为探针, 测定它在表面活性剂(C12TABr、SDS、C12E23、C12-3-12·2Br)水溶液中的第二重荧光强度(Ia)和对应的特征波长(λa)对表面活性剂浓度(c)曲线, 由Ia-c 曲线的转折点或λa-c曲线对应的一阶导数极小点可以获得临界胶团浓度(cmc). 由于C12-3-C12·2Br在水溶液中强烈聚集, 利用λa-c曲线还可以获得其胶团结构松散度的信息.     

Preferential Solvation in Aqueous–Organic Mixed Solvents Using Solvatochromic Indicators

Solvatochromism of the twisted intramolecular charge-transfer (TICT) fluorescence of 4-(N,N-dimethylamino)benzonitrile (DMABN) in pure water, methanol, ethanol, 1-propanol, 2-propanol, acetone, acetonitrile, and in the corresponding aqueous–organic binary mixed solvents was systematically studied and an empirical solvent polarity scale (F _B) based on the DMABN solvatochromism was defined. The F _B parameters of the explored binary mixed solvents as a function of solvent composition were analyzed by a stepwise solvent-exchange (SSE) model to clarify the preferential solvation (PS) of the probe dye in these binary mixed solvents. Solvation diagrams toward DMABN in the mixed solvents, i.e., the local solvent composition in the solvation shell of DMABN molecules was depicted as a function of bulk solvent composition to visualize the PS in these mixed solvents. For comparison, a similar PS analysis was applied to the solvatochromism of 2,6-diphenyl-4-(2,4,6-triphenylpyridinium-1- yl)phenolate (ET-30) and pyrene (Py) in these mixed solvents; the responsive PS pattern of the mixed solvents toward the specific indicator dye of DMABN, ET-30, and Py was then discussed in terms of the chemical properties of the probe dye, the properties of the mixed solvents, and the solute–solvent and solvent–solvent interactions.     

DMABN在表面活性剂胶束水溶液中的荧光性质

研究了对二甲氨基苯甲腈(DMABN)在各种胶束水溶液中的荧光光谱性质, 发现不同胶束栅栏层区域的不同性质影响了探针的分子内扭转电荷转移(TICT)特性. 对离子型胶束, 头基电场是主要影响因素, 促进了DMABN分子TICT态的形成, 反离子解离度琢越大, 胶束溶液中的Ia/Ib越强. 在非离子表面活性剂胶束中, 聚氧乙烯链环外壳包裹的大量水使其氢键影响明显, 而很短的聚氧乙烯链还可能带来端基氢的氢键作用. 从DMABN的光物理特性看, 欲将胶束作为分散载体利用其TICT态特性, 选择反离子解离度较大的阴离子胶束(例如SDS或SDSO)较好.     

A new 4-(N,N-dimethylamino)benzonitrile (DMABN) derivative with tetrathiafulvalene unit: modulation of the dual fluorescence of DMABN by redox reaction of tetrathiafulvalene unit

A new derivative of 4-(N,N-dimethylamino)benzonitrile (DMABN) (compound 1) with TTF unit is reported. Compound 1 exhibits dual fluorescence, and moreover the dual fluorescence behavior can be modulated by reversible oxidation and reduction of TTF unit of 1 either chemically or electrochemically. Accordingly, a new molecular fluorescence switch is realized by coupling the features of TTF and DMABN.     

Determination of the Critical Micelle Concentration of Surfactant in Aqueous Solution by Twisted Intramolecular Charge Transfer Probe DMABN

With p-N,N-dimethylaminobenzonitrile (DMABN) as a probe, the variations of the intensity of its second fluorescence emission (I_a) and the corresponding characteristic wavelength (λ_a) with the surfactant concentration (c), here the examined surfactants (C₁₂TABr, SDS, C₁₂E₂₃, and C₁₂-3-C₁₂·2Br), were measured by Hitachi F4500 fluorescence spectrophotometer. The results showed that both the break points on the I_a–c curve and the minimum of the derivative variation corresponding to the λ_a–c curve agreed very well with the critical micelle concentration (cmc) of the surfactant in aqueous solution as measured by surface tension technique. Due to strong aggregation of C₁₂-3-C₁₂·2Br in aqueous solution, the information about loose micellar structure could be obtained by its λ_a–c curve.     

Influence of solvent basicity on DMABN photophysics

¹H‐NMR resonance measurements of 4‐(dimethylamino)benzonitrile (DMABN), dissolved in dichloromethane at temperatures over the range 300–195 K, confirm that the electronic charge transfer from its dimethylamino group to its cyano group increases with increasing dipolarity of the solvent and hence that the twisted internal charge transfer form of DMABN can be directly created by excitation of its electronic ground state. However, in tetrahydrofuran and 1,4‐dioxane, the DMABN molecules form complexes with the solvent, hindering charge transfer and reducing the electron‐releasing capability of the dimethylamino group. Irradiating a dilute solution of DMABN with an intensity as low as 7.8 × 10¹³ photons/s causes the formation of 4‐(methylamino)benzonitrile as photoproduct. The emission spectra of DMABN exhibit an isoemission point at a wavelength that is shifted with an increase in solvent dipolarity. The high efficiency with which the photoproduct is obtained seems to depend on the basicity of the solvent and challenges some former photophysical conclusions not considering this fact and drawn by using stronger irradiation sources, as well as the potential use of DMABN‐like compounds as solvent viscosity probes. Copyright © 2016 John Wiley & Sons, Ltd.