Encapsulation of tetraazaannulenato compounds in matrix by sol-gel process

摘要

The hybrid organic-inorganic catalyst constituted by {5,7,12,14-tetramethyldibenzo[b,i]-1,4,8,11-tetraaza[14]annulenato} nickel (II),NiTMTAA,encapsulated in an alumina matrix has been prepared.nITMTAA was synthesized by the reaction of nickel acetate with o-phenylenediamine in the presence of 2,4-pentanedione under argon atmosphere.The alumina hybrid material was obtained by a non hydrolytic sol-gel route,through the condensation of aluminum chloride with diisopropylether in the presence of NiTMTAA.The material has been prepared through precipitation from a gel.Characterization of the alumina hybrid material has been performed by ultra violet-visible spectroscopy,electron spectroscopic imaging,surface area,atoms absorption,infrared spectroscopy,and thermogravimetric analysis.The ultra violet-visible absorption spectrum of the hybrid material has bands characteristic of the NiTMTAA compound showing that the structure of NiTMTAA has been preserved in the hybrid materiaL.The new material has a surface area of 300 m~2/g.The electron image was that of a non-crystalline microstructure.Comparison between the leaching of NiTMTAA from NiTMTAA adsorbed on commercial neutral alumina confirm that in the non-hydrolytic sol-gel process leads to the complete leaching of NiTMTAA from matrix,underlining the importance of the non-hydrolytic alumina gel process in the matrix preparation.The new catalysts pepared were tested for their ability to catalyze the epoxidation of (Z)-cyclooctene using iodosylbenzene as oxygen donor,giving moderate yields in the epoxidation (40%),while the homogeneous NiTMTAA is inactive due to NiTMTAA bleaching.These results emphasize the effect of the non-hydrolytic alumina matrix to prevent chemical degradation of NiTMTAA.