Mixed ligand complexes of trivalent lanthanide ions with β-diketones and heterocyclic amines and their use as possible shift reagents

Abstract Sixty new complexes of the trivalent lanthanides (except Pm and Lu) and Yttrium of the general formulae, Ln(TFAA) 3 o-phen, Ln(TFAA) 3 dipy·2H 2 O, Ln(dpm) 3 im, Ln(dpm) 3 pz, and Ln(fod) 3 o-phen where TFAA = trifluoroacetyl-acetone-H, dpm = 2,2,6,6-tetramethyl 3,5-heptane dione-H, fod = 1,1,1,2,2,3,3-heptafluoro, 7,7-dimethyl 4,6-octane dione-H, o-phen = 1,10-phenathroline, dipy = 2,2′dipyridyl, im = imidazole and pz = pyrazole, have been synthesised and characterised by elemental analyses, melting points, molar conductance, magnetic susceptibility, thermogravimetric analysis, and IR spectral studies. The trivalent lanthanide ions have a coordination number of ten in the series Ln(TFAA) 3 dipy·2H 2 O. Their avidity to enhance their coordination number is so great that een in the presence of three such bulky ligands as heptafluorooctane dione the Ln(fod) 3 still coordinates with o-phen. Hexacoordinated trivalent lanthanides act as LIS reagents but it has been observed that even the eight coordinated and very bulky Pr(fod) 3 o-phen produces dipolar shifts in the proton resonances of organic moities.