Antiozonant activity of the silica modified with 3d metal complexes

Mono- and Bimetallic Complexes of Mn(II), Co(II), Cu(II), and Zn(II) with Schiff Bases Immobilized on Nanosilica as Catalysts in Ozone Decomposition Reaction

“…As shown in the previous papers [1,[14][15][16][17], the firstorder reaction rate constants can be calculated in many cases from the initial portions of kinetic curves of ozone decomposition. Their values are invariable at the beginning of the reaction but change at the half-conversion time confirming the radical chain mechanism of the reaction.…”

“…The results of analyzing kinetic (τ 1/2 , k 1/2 ) and stoichiometric (Q exp , n) parameters for all nanocomposites under study are summarized in Table 3. Based on the classic conceptions concerning the mechanism of ozone decomposition [2][3][4] and our studies of kinetics of ozone decomposition by 3d metal complexes with Schiff bases immobilized on nanosilica [1,[14][15][16][17], it can be deduced that metal ions taking part in the chain propagation reaction increase the time of ozone halfconversion attainment (k 1/2 decreases) and the amount of ozone entering the reaction over the whole period of its proceeding (Q exp ). In this case, the higher the τ 1/2 and Q exp the more actively complex decomposes ozone.…”

“…In the presence of mentioned complexes, similarly to the reaction in solutions [2][3][4], the ozone decomposition proceeds by the radical chain mechanism, the kinetic proof of which can be the difference between the values of first-order reaction rate constant at the beginning of the reaction and at the ozone half-conversion time. Consequently, metal complex 1 Odesa I.I. Mechnikov National University, 2, Dvoryanska St., 65082 Odesa, Ukraine 2 Kyiv Taras Shevchenko National University, 64, Volodymyrska St., 01601 Kyiv, Ukraine 3 National University of Kyiv-Mohyla Academy, 2, Skovorody St., 04655 Kyiv, Ukraine * truba@onu.edu.ua © Rakitskaya T., Truba A., Radchenko E., Golub A., 2018 catalytic effect for these reactions is determined not only by the nature of complexing ion and ligand, but by the existence of even insignificant impurities of another metal ion.…”

“…Previously, it has been shown that the catalytic activity of 3d metal complexes МL 2 / Si (or МL 2 /SiO 2 ) immobilized on silicas [aerosil А-300 (Si ), silica KSMG (SiO 2 )] strongly depends not only on the nature of the metal М = manganese(II), cobalt(II), copper(II), zinc(II), the ligand (L = Schiff bases, NO − 3 , Cl -), the geometry of coordination polyhedron, but also on the nature of the matrix [1]. As a result, the specific antiozonante activity of monometallic compositions immobilized on nanosilica exceeds by two orders the activity of complexes on porous matrix МL 2 /SiO 2 (L = NO ).…”

Manganese(II) Complexes with Schiff Bases Immobilized on Nanosilica as Catalysts of the Reaction of Ozone Decomposition

“…In the latter case, an access of reagents to the immobilized complexes and, consequently, the kinetics of the reaction are determined by internal diffusion factors. Intradiffusious inhibition of the reaction with metal-Schiff base complexes can be avoided if non-porous pyrogenic nanosilica (aerosil) with developed outer surface is used as a carrier [ 25 ]. It should be noted that manganese(II) becomes manganese(III, IV) in the course of the synthesis of immobilized complexes with Schiff bases on the noted carriers, except nanosilica [ 25 ] and aminated silica [ 17 ].…”