Abstract: In this work, acetic acid functionalized pyridinium salt, namely 1-(carboxymethyl)pyridinium iodide {[cmpy]I}, has been applied as reusable nanostructured catalyst for green, simple and efficient preparation of spiropyrans by the one-pot domino Knoevenagel–Michael–cyclization reaction of isatin derivatives or acenaphthenquinone, with malononitrile, and 1,3- dicarbonyl compounds under aqueous media. Moreover, 1H and 13C NMR, mass, CHN analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), thermal gravimetric analysis (TGA), differential thermal gravimetric (DTG), X-ray diffraction analysis (XRD), and calculation of crystallite size and interplaner distance of the catalyst have been studied.
