Comparative study of cerium-manganese ratios in the design of Ce-Mn-binuclear LDH-based Cu complex: a potent nanocatalyst for the green synthesis of spiro[acridine-9,3'-indole]triones.

The Ce-Mn binuclear LDH was prepared at four different molar ratios of Ce to Mn (1:1, 1:2, 1:3, and 1:4), modified with both 3-chloropropyltrimethoxysilane (CPTMS) and N-amino-phthalimide (NAP), complexed with Cu(II), and characterized by the FT-IR, ICP, XPS, XRD, BET, UV/Vis, EDX, SEM, SEM-mapping, TEM, and TGA-DTA techniques. The ICP, XPS, BET, and UV-vis techniques showed that the 1:4 molar ratio of Ce to Mn is the best, therefore it was used as a heterogeneous nanocatalyst for the green synthesis of fourteen spiro[acridine-indole]triones from the three-component condensation reaction of isatin, aniline, and 1,3-diketone in mild reaction conditions. The advantages of this method include the absence of harmful organic solvents, easy separation of the catalyst and products, and rapid achievement of excellent yields. Furthermore, the activity of the catalyst was maintained even after four consecutive runs without a significant loss of activity.