Study Of Polydentate Schiff Bases And Transition Metal Complexes On Calix[4]arene Platform

Calixarenes have attracted much attention in recent years for their unique structural and chemical diversity, which allow their use in the synthesis of various molecular architectures. The research in the coordination chemistry of calixarenes has shown the vast ability of these compounds as selective binders, carriers and also as building blocks for the construction of highly complexes. Schiff bases have been employed widely in the formation of metal complexes and in the study of inclusion phenomena, owing to their relatively easy preparation, remarkable stability and high versatility. The fusion of the Schiff base and calixarene properties into a unique entity can give rise to interesting and versatile system with very peculiar coordination properties. Although the study of calixarene Schiff bases as ion recognition, extraction and transportation have long been established, it seems that the study of preparation and crystal structures of has not yet been investigated in detail. In this work we studied the synthesis and complexing properties of polydentate Schiff bases ligands on calix[4]arene platform. Some of significant and creative results are showed as follows:1. Seven calix[4]arene derivatives with aldehyde functions have been synthesized through improved efficient procedures, which in turn reacted with semicarbazide and thiosemicarbizide to form a series of calixarene-based semicarbazone and thiosemicarbazone polydentate ligands. Their structures are characterized by 1H, 13C NMR and IR spectroscopy and were further confirmed by X-ray diffraction determination of three representative single crystals.2. Several calix[4]arene-based podands which incorporates two Schiff base functions in 1,3-alternate position at lower rim has been prepared by the condensation of calixarene aldehyde derivatives with S-methyldithiocarbazate and S-benzyldithiocarbazate. Their structures are characterized by 1H, 13C NMR and IR spectroscopy and were further confirmed by X-ray diffraction determination of two representative single crystals. 3. The complexation of calix[4]arene-based Schiff base ligands with transition metal ions were studied. The structures of the prepared transition metal complexes were prelimarily characterized. The X–ray single crystal diffraction of nickel and copper complexes shows that two iminothiolate domains act as monoanionic bidentate planar chelators to coordinate to one metal ion.