Synthesis of novel styryl derivatives from 4-chloro-2-(morpholin-4-yl)-1,3-thiazole-5-carbaldehyde, study of their photophysical properties and TD-DFT computations
Introduction
The chromophoric systems like coumarins, acridines, perylenes, xanthenes, methines, hemicyanines and cyanines have good fluorescence property [1]. Among all the chromophoric systems, methine or styryl class of fluorophores are found to be the most interesting due to the ease of synthesis, purification and properties such as bright hue and high photostability [2]. They have been extensively studied as solar energy collectors [3], [4], organic light emitting diodes (OLED) [5], non-linear optical materials, [6], [7], organic semiconductors [8], probes for bioimaging [9], [10], [11], [12], metal ions as well as organic vapor sensors [13], [14], [15], [16].
The styryl chromophores having thiazole nucleus occur in NLOphoric materials [17], reactive dyes [18] and disperses dyes [18], [19]. The textile colorants based on thiazole show excellent wet fastness and light fastness properties [19], [20]. The incorporation of a cyano group into a styryl dye enhances both the bathochromicity and the sublimation fastness of the dyes. As a part of the ongoing research [21] on the styryl colorants, we report here novel styryl analogs based on 4-chloro-2-(morpholin-4-yl)-1,3-thiazole-5-carbaldehyde having solid state fluorescence.
Section snippets
Materials and equipments
All the commercial reagents and solvents were procured from s.d. fine chemicals (India). The reaction was monitored by TLC using 0.25 mm E-Merck silica gel 60 F254 precoated plates, which were visualized with UV light. Melting points were measured on standard melting point apparatus from Sunder Industrial Product, Mumbai, and are uncorrected. The FT-IR spectra were recorded on a Perkin–Elmer Spectrum 100 FT-IR Spectrometer. 1H-NMR spectra were recorded on VXR 300 MHz instrument using TMS as an
Photophysical properties
The compounds 9a–9c show solid state fluorescence while the compound 9d with the barbituric acid unit does not fluoresce in the solid state (Fig. 1a). The photograph of the compounds 9a–9c is shown in Fig. 1b. The compound 9a shows solid state absorption maxima at 430 nm and emission maxima at 563 nm. In the case of the compound 9b the solid state maxima was observed at 446 nm and the emission maxima at 606 nm. The absorption maxima of the compound 9c in the solid state is similar to the compound 9a
Conclusion
In summary, we have developed an efficient and a simple protocol for the synthesis of the fluorescent styryl derivatives from the intermediate 4-chloro-2-(morpholin-4-yl)-1,3-thiazole-5-carbaldehyde. The synthesized D-π-A type styryl derivatives were confirmed by FT-IR, 1H-NMR and mass spectral analysis. The synthesized dyes have good thermal stability and have solid state fluorescence. The dye 9c has excellent solid state fluorescence. The solvatochromism and solvatofluorism studies in
Acknowledgments
The authors (Prashant Umape and Rajratna Tayade) are thankful to UGC for providing fellowship under UGC-SAP programme. Vikas Padalkar is thankful to the Institute of Chemical Technology for encouragement.
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