Īmong dyestuffs classes, the push-pull fluorescent dyes are renowned to own such special behaviors. Moreover, some fluorescent dyes demonstrate remarkable ICT characteristics, and could therefore serve as NLO dyes. Fluorescent dyes as chemosensors offer unique merits such as low energy consumption, ease of handling, high selectivity, and notable sensitivity. These dyes show different spectral properties upon protonation/deprotonation processes. Therefore, pH-sensitive dyes play a critical role in various sensor applications for easy determination of such ions. Their presence in aqueous media directly determines the pH level that affects organisms living in the corresponding area. Some ions such as proton (H +) and hydroxide (OH −), in aqueous environments, play significant roles in industrial, biological, and environmental processes. The flexibility to change electron-donor and acceptor groups in the molecules allows to tune intramolecular charge transfer (ICT) intensity and it can increase NLO properties. Nowadays, organic NLO materials bearing strong donor–acceptor groups with a π-bridge have shown extensive usages in signal processing, optical storage, and telecommunication devices. One important feature of these molecules is an exceptional polarizability which is a crucial criterion for NLO materials. The dyes exhibit strong absorption and emission properties in solution and in the solid state. Push-pull organic molecules are a class of organic dyes comprising of electron-donating and accepting groups in a donor–π–acceptor (D–π–A) system. The TGA data showed that all dyes were thermally stable up to 250 ☌. The thermal stabilities of all dyes were evaluated by thermogravimetric analysis (TGA). The structural and electronic properties of the dyes as well as their NLO properties were further studied using DFT calculations. 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 second-order nonlinear optical (NLO) responses of the dyes were measured by the electric field-induced second harmonic (EFISH) generation method. Therefore, they showed potential to be utilized as colorimetric and luminescence pH sensors. ![]() ![]() The Schiff bases exhibited a bathochromic shift upon the addition of TBAOH to their solutions in DMSO. 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. ![]() However, there was no correlation with the polarity parameters of the solvents. The absorption and the emission maxima were shifted bathocromically by increasing the solvent’s polarity. 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. 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 dyes include the dicyanomethylene group as an acceptor and different para-substituted alkylamines as donors. 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.
0 Comments
Leave a Reply. |