Publications – João Costa Pessoa - 2008

Short Abstract 3-Formylsalicylic acid (Hfsal) covalently bound to chloromethylated polystyrene (PS) cross-linked with 5% divinylbenzene reacts with DL-alanine and L-isoleucine to give the Schiff-base tridentate ligands PS-H2fsal-DL-Ala and PS-H2fsal-L-isoleu, respectively. These anchored ligands on reaction with VOSO4 and Cu(CH3COO)2.H2O form complexes PS-[VO(fsal-DL-Ala)(H2O)], PS-[Cu(fsal-DLAla)(H2O)], PS-[VO(fsal-L-Ile)(H2O)] and PS-[Cu(fsal-L-Ile)(H2O)]. Structures of these immobilized complexes have been established on the basis of scanning electron micrographs, spectroscopic (Infrared, electronic and EPR), thermo gravimetric and elemental analyses studies. Oxidation of pchlorotoluene and cyclohexene has been investigated using these complexes as catalyst in the presence of H2O2 as oxidant. Recycling studies indicate that these catalysts can be reused at least three times without any significant loss in their catalytic potential. However, EPR studies indicate that while the polymer supported VO-complexes do not change upon use, the EPR spectra of the Cucomplexes show significant changes. The corresponding non-polymer-bound complexes [VO(fsalDL-Ala)(H2O)], [Cu(fsal-DL-Ala)(H2O)], [VO(fsal-L-Ile)(H2O)] and [Cu(fsal-L-Ile)(H2O)] have also been prepared to compare their spectral properties and catalytic activities. Non-polymer-bound complexes exhibit lower conversion along with lower turn over frequency as compared to their polymer-bound analogues. Several EPR, V NMR and UV-Vis studies have been undertaken to detect intermediate species, and outlines of the mechanisms of the catalytic reactions are proposed.