The Influence of the Number and Position of the Methoxy Group on the Physicochemical Properties and Possible Applications of Rhodanine-3-Acetic Acid Derivatives

In this study, we investigated the effect of the number and position of the methoxy group substitution on selected physicochemical and biological properties of rhodanine-3-acetic acid derivatives. We conducted our studies on a group of eight compounds (C-1–C-8) obtained by Knoevenagel condensation, with yields ranging from 49% to 99%. All synthesized compounds were thermally stable above 240 °C. Luminescence studies revealed the ICT nature of the absorption and emission spectra. Derivative C-4 exhibited the greatest blue shift, while compounds C-7 and C-8 exhibited the greatest red shift. Furthermore, our results indicate that compound C-2 is the best candidate from the entire group for reliable, artifact-free cytoplasmic staining. C-2 achieves excellent contrast in the FITC/Alexa488 channel while maintaining statistically unchanged 3T3 metabolic activity. In terms of antibacterial activity, the best results were obtained for the C-1 derivative, which demonstrated mild to moderate activity against Gram-positive bacteria. Compound C-8 demonstrated the highest anticancer activity against cancer cells such as SNB-19, Caco-2, and A2058.