Ship-in-a-bottle synthesis and physicochemical studies on zeolite encapsulated Mn(II), Mn(III)-semicarbazone complexes: application in the heterogeneous hydroxylation of benzene

Abstract

Complexes of Mn(II) and Mn(III) with semicarbazone ligand (SALSC) derived from salicylaldehyde and semicarbazide have been occluded in zeolite-Y supercages by a diffusion method. The synthesized host/guest materials have been isolated and characterized by various physico-chemical techniques. The results have revealed that, SALSC can coordinate with the central metal ions via the (C=N), deprotonated enolic (C=O) and phenolic (OH) groups. Investigation of the stereochemistry pointed out that, the intrazeolitic manganous and manganic semicarbazone complexes have a 1M:2L tetrahedral and 1M:1L penta-coordinate structures, respectively. The catalytic activity of the samples was evaluated towards benzene hydroxylation at 80 °C and the results showed a stimulation activity to give phenol with the sequence MnII-Y > MnIII(SALSC)/Y > MnII(SALSC)/Y.