Synthesis, spectral and magnetic studies on 4-nicotinyltrifluoroacetonates of La(III), Pr(III), Sm(III), Ho(III) and Er(III)

Dihydrated and anhydrous chelates of La(III), Pr(III), Nd(III), Sm(III), Ho(III) and Er(III) with 4-nicotinyltrifluoroacetone [4,4,4-trifluoro-1-(4-pyridyl)-1,3-butanedione] have been synthesised for the first time and characterized on the basis of analytical, molecular weight, IR and electronic spectral, and magnetic moment data. The substitution of hydrogen of methyl group by electronegative fluorine in 4-nicotinylacetonates strengthens the C-O and C-C bonds. The anhydrous chelates are dimeric in benzene but in polar solvents like dimethylformamide, the molecular complexity lies around 1.75. Calculation of various bonding parameters, e.g. nephelauxetic ratio (β), percentage covalency parameter (delta) and bonding parameter (bsup(1/2)), from the electronic spectral data, indicates the incidence of some covalent character in the metal-ligand bond. Magnetic moments of the hydrated complexes and their anhydrous analogues are almost same. (author)