Trend of Stabilities of Adducts of 4,4,4-Trifluoro-1-(2-thienyl)-1,3-butanedionates with Phenylpyridines over Lanthanoid Series

1995 Analytical Sciences  
The formation constants of the adducts of 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionatolanthanoids(III) with 2-, 3-, and 4-phenylpyridines as well as the distribution constants and pKa of these pyridines were determined on the basis of data obtained by solvent extraction from a 0.1 molldm3 sodium perchlorate solution into chloroform containing TTA and/or pyridines. It has been found that the adduct formation constants(}) of a given lanthanoid(III) chelate increase along with increased pKa of
more » ... h increased pKa of the phenylpyridine, and that the constants do not change much from light to middle lanthanoids, and then decrease for heavy ones. The constants for the 2-phenylpyridine adduct are lower than expected, possibly reflecting a steric effect. The pattern of a plot of log ail versus the atomic number is different from that with carboxylic acids and bidentate amines.
doi:10.2116/analsci.11.59 fatcat:5v2jjbtuwbdmlnkodh5tzvpjke