Influence of water on photophysical properties of N-bromobenzyl- or nitrobenzyl derivatives of substituted 4-hydroxystilbazolium hemicyanines
作者:Dorota Prukała、Wiesław Prukała、Igor Khmelinskii、Jerzy Karolczak、Marek Sikorski
DOI:10.1039/c1pp05119a
日期:2011.10
Absorption, steady-state and timed-resolved fluorescence spectra of nine N-p-bromobenzyl substituted (E)-4′-hydroxy-4-stilbazolium bromides and N-p-bromo- (or nitro-) benzyl substituted (E)-4′-hydroxy-3′methoxy-4-stilbazolium bromides, belonging to the hemicyanine class of compounds, were studied in dry and water-containing polar solvents and in water. All of the studied compounds displayed negative solvatochromism. In solvents with small amounts of water the solutions of each of the compounds change color to red, blue-green or blue, while in extra dry solvents they are all yellow. The new band causing the change in color is interpreted as belonging to the deprotonated form of the respective compound. The absorption and emission spectra of protonated and deprotonated forms of hemicyanines in solvents are presented in comparison with those of selected, isolated deprotonated forms (merocyanines) of the same compounds. The discrimination between the quinoid and zwitterionic deprotonated forms was achieved based on the absorption band location. Time-resolved fluorescence measurements in selected dry and water-containing solvents were also performed.
在干燥和含水极性溶剂以及水中,研究了九种 N-对溴苄基取代 (E)-4′-hydroxy-4-stilbazolium 溴化物和 N-对溴(或硝基)苄基取代 (E)-4′-hydroxy-3′methoxy-4-stilbazolium 溴化物的吸收、稳态和定时分辨荧光光谱、在干燥和含水极性溶剂中以及在水中研究了属于半氰胺类化合物的 N-溴和 N-溴化苄取代 (E)-4′-羟基-3′-甲氧基-4-苯并唑溴化物。研究的所有化合物都显示出负溶解色度。在含有少量水的溶剂中,每种化合物的溶液都会变为红色、蓝绿色或蓝色,而在超干溶剂中,它们都是黄色的。引起颜色变化的新色带被解释为属于相应化合物的去质子化形式。图中展示了质子化和去质子化半氰胺在溶剂中的吸收光谱和发射光谱,并与同类化合物中选定的、分离的去质子化形式(美拉氰胺)的吸收光谱和发射光谱进行了比较。根据吸收带的位置,可以区分醌类和齐聚物去质子化形式。此外,还在选定的干燥溶剂和含水溶剂中进行了时间分辨荧光测量。