Preparation and investigation of Ce(III), Th(IV) and U(VI) chelates with some Schiff bases derived from 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one

Schiff bases were prepared by condensation of equimolar amounts of 5,7-dihy droxy-6-formyl-2-methylbenzopyran-4-one and aniline, anthranilic acid, 2-am inophenol, 5-chloro-2-aminophenol or 4-amino-3-hydroxybenzenesulphonic acid . The molecular structure of the prepared Schiff bases was confirmed by mas s and UV spectra. The chelates of Ce(III), Th(IV), and U(VI) with the above Schiff bases were prepared. All the prepared compounds were subjected to e lemental analyses for C, H, N, Cl, S and metal (for the chelates), IR and H -1 NMR spectroscopy. The studies show that Ce(III) and Th(IV) give 1:1, 1:2 and 2:1 (M:L) metal chelates, while U(VI) gives only 1:1 and 1:2 (M:L) che lates. This may be attributed to the difficulty of coordinating two bulky u ranyl ions to the same molecule because of their steric effect. The studies revealed that the Ce(III) and Th(IV) chelates exhibit octahedral structure with the coordination number 6 while U(VI) chelates exhibit dodecahedral s tructure with the coordination number 8. Thermogravimetric analysis data we re obtained for some of the prepared chelates.