Nickel(II) and manganese(III) tetraazaannulenes complexes encapsulated in porous Vycor glass (PVG): investigation of catalytic activity

Abstract

The first immobilization of Ni(II) and Mn(III) metallotetraazaannulene compounds in nanometric pores of an inorganic matrix (porous Vycor glass, PVG) by diffusion of the complex through the glass pores is reported. The immobilization process was monitored by UV–vis spectroscopy at room temperature and electron paramagnetic resonance spectroscopy (EPR) at 77 and 300 K. Results showed that the manganese(III)complex was reduced inside the PVG after the immobilization process. On the other hand, the NiTMTAA (tetramethyl dibenzotetraaza[14]annulene of nickel(II)) remained stable. The catalytic activity of NiTMTAA as model of Factor F430 on the reductive dehalogenation of alkyl halides (iodocyclohexane or bromocyclohexane) was studied in homogeneous and heterogeneous systems in the presence of NaBH4 as reducing agent. The promising catalytic results have shown adequate characteristics of PVG for immobilization of the Ni(II) tetraazaannulene complex. These nanocomposites display high potential for heterogeneous catalytic procedures.