Synthesis and Spectroscopic Study of a New Lanthanum(III) Complex of 3,3′‐Benzylidenedi‐4‐hydroxycoumarin

Abstract The coordination ability of 3,3′‐benzylidenedi‐4‐hydroxycoumarin (H2bhc) has been proved in a complexation reaction with lanthanum(III) ion. The new lanthanum(III) complex of bhc2− was studied by elemental analyses, mass spectra, 1H, 13C NMR, and IR spectroscopy. The data obtained are in agreement with the metal:ligand ratio of 1:l, and the formula La(bhc)(OH)(H2O), where bhc2− = C25H14O6 2−. The calculated condensed Fukui functions for bhc2− predicted that both hydroxyl and carbonyl oxygen atoms are probable reactive sites for coordination to the metal. The vibrational analysis of the lanthanum(III) complex, free H2bhc, bhc2−, and 4‐hydroxycoumarin showed that in the La(III) complex the ligand coordinates to the metal ion through both deprotonated hydroxyl groups. The participation of both carbonyl groups in coordination to the metal ion was confirmed by the significant shift of ν(C˭O) to lower wave number.