Green synthesis of ethyl cinnamates under microwave irradiation: photophysical properties, cytotoxicity, and cell bioimaging.

A simple and green method for the synthesis of six ethyl cinnamates was performed via Horner-Wadsworth-Emmons reaction under microwave irradiation. The photoluminescent properties of all compounds in ethyl acetate solutions were evaluated demonstrating that all compounds exhibit fluorescence. Five compounds exhibited blue emissions in the 369-442 nm range, and another compound exhibited blue-green emission at 504 nm. This last compound showed the largest Stokes shift (134 nm), and the highest quantum yield (17.8%). Two compounds showed extinction coefficient values ( ε ) higher than 30 000 M -1 cm -1 , which are appropriate for cell bioimaging applications. In this sense, cytotoxicity assays were performed using Vero cells at different concentrations; the results showed that these compounds were not cytotoxic at the highest concentration tested (20 μg mL -1 ). Finally, the analysis by fluorescence microscopy for localization and cellular staining using Vero cells demonstrated that the compounds stained the cytoplasm and the nuclei in a selective way.