Antipyrilquinoneimine dye formation by coupling aniline derivatives with 4-aminoantipyrine in the presence of ruthenium nanoparticles

The coupling of 4-aminoantipyrine with aniline derivatives catalyzed by ruthenium nanoparticles has been studied by UV-Vis spectroscopy in aqueous medium. The rate constant for antipyrilquinoneimine dye formation depends on the nature of the aniline substituent and the p H, ionic strength and temperature of the reaction medium. The maximum rate constant of the dye formation reaction is observed at p H 3.6. Aniline derivatives with electron donating substituents show higher rate constant values than those with electron withdrawing substituents, with increasing rate constant values in the order: N,N-dimethyl aniline> a-toluidine> o-chloroaniline > m-chloroaniline. With pseudo first order kinetics, the total order is 1.0 + 1.0 + 1.0 = 3.0, which includes the orders with respect to amine, 4-aminoantipyrine and ruthenium nanoparticles. Studies on these effects help to complete the kinetic analysis as well as propose the reaction pathway. Furthermore, TEM measurement confirms that the nano scalar size of the ruthenium nanoparticles is 7 nm