Synthesis and characterization of lanthanoid(III) complexes with a pentadentate ligand derived from 2,6-diacetylpyridine and benzoylhydrazide

Abstract

The pentadentate ligand 2,6-diacetylpyridine-bis(benzoylhydrazone) (abbreviated as dapph) was shown to form lanthanoid(III) complexes with the general formula Ln(dapph)(NO 3) 3(H 2O) n( n = 0–2); the La to Eu complexes were obtained as monohydrates, the Tb to Lu complexes as dihydrates, and the Gd complex as an anhydrate. The complexes are classified into two groups based on IR spectral patterns of the nitrate ions: the La to Gd complexes and the Tb to Lu complexes. In the former complexes all three nitrate ions function as bidentate ligands, whereas the latter complexes contain both bidentate and unidentate nitrate ions. Based on 13C NMR spectra, it was suggested that the ligand dapph forms more stable complexes with the heavier metal ions (TbLu) compared to the lighter metal ions (LaGd).