Herein we report the synthesis and characterization of a new series of styryl-based push-pull dyes containing a free amino group and their Schiff base derivatives. The dyes include the dicyanomethylene group as an acceptor and different para-substituted alkylamines as donors. Morever as a proton-sensitive group a pyridin-2-yl substituent was attached to the para-position of the phenyl moiety in both series of compounds. The photophysical properties of the dyes were examined in various solvents with different polarities and showed absorption in the visible region and green-red emission with low quantum yields. The absorption and the emission maxima were shifted bathocromically by increasing the solvent’s polarity. However, there was no correlation with the polarity parameters of the solvents. The pH-sensitive properties of all prepared Schiff bases were examined against TBAOH in DMSO, via deprotonation of the OH group in the salicylidene moiety and their reverse protonation was also investigated using TFA. The Schiff bases exhibited a bathochromic shift upon the addition of TBAOH to their solutions in DMSO. Therefore, they showed potential to be utilized as colorimetric and luminescence pH sensors. The second-order nonlinear optical (NLO) responses of the dyes were measured by the electric field-induced second harmonic (EFISH) generation method. The highest μβ values were obtained for the dyes bearing the julolidine donor as 1430 × 10⁻⁴⁸ esu (for free amino derivative) and 1950 × 10⁻⁴⁸ esu (for Schiff base derivative), respectively. The structural and electronic properties of the dyes as well as their NLO properties were further studied using DFT calculations. The thermal stabilities of all dyes were evaluated by thermogravimetric analysis (TGA). The TGA data showed that all dyes were thermally stable up to 250 °C.

中文翻译：

---

基于苯乙烯基的新型有机发色团，带有游离氨基和甲亚胺基：合成，光物理，NLO和热性质

在这里，我们报告合成和表征的一系列新的基于苯乙烯基的推挽式染料，其中包含一个游离氨基及其席夫碱衍生物。染料包括二氰基亚甲基作为受体和不同的对位取代的烷基胺作为供体。此外，作为对质子敏感的基团，吡啶-2-基取代基连接到对两个系列化合物中苯基部分的-位。在具有不同极性的各种溶剂中检查了染料的光物理性质，并显示了在可见光区域的吸收和绿红色发射，且量子产率低。通过增加溶剂的极性，吸收和发射最大值发生了方差变化。但是，与溶剂的极性参数无关。通过在水杨基亚烷基部分中的OH基团去质子化，检查了所有制备的席夫碱对DMSO中的TBAOH的pH敏感性，并使用TFA研究了它们的反向质子化。将TBAOH添加到DMSO溶液中后，席夫碱表现出红移。因此，它们显示出可用作比色和发光pH传感器的潜力。染料的二阶非线性光学（NLO）响应是通过电场诱导的二次谐波（EFISH）生成方法测量的。含菊糖苷供体的染料的最高μβ值为1430×10^-48 esu（对于游离氨基衍生物）和1950×10 ^-48 esu（对于Schiff碱衍生物）。使用DFT计算进一步研究了染料的结构和电子性能以及其NLO性能。通过热重分析（TGA）评估所有染料的热稳定性。TGA数据表明，所有染料在高达250℃的温度下都是热稳定的。