Preparation, luminescent properties of N-phenyl-2-{2′-[(phenyl-ethyl-carbamoyl)-methoxy]-biphenyl-2-yloxy}-N-ethyl-acetamide (L) lanthanide complexes and the supramolecular structures of [La(pic)3L] and 2[La(NO3)3L(H2O)] · H2O · 0.5C2H5OH

A new amide-based ligand, N-phenyl-2-{2′-[(phenyl-ethyl-carbamoyl)-methoxy]-biphenyl-2-yloxy}-N-ethyl-acetamide (L) was synthesized. Solid complexes of lanthanide picrates with this new ligand were prepared and characterized by elemental analysis, conductivity measurements, IR, electronic and 1H NMR spectroscopies. Under excitation, the europium picrate complex exhibited strong characteristic emissions. The europium nitrate complex exhibited quite weak characteristic emissions. The counter anion factor influencing the fluorescence properties was discussed. The lowest triplet state energy level of the ligand in the picrate complex matches better to the resonance level of Eu(III) than Tb(III) ion. The crystal structures of the complex La(Pic)3L and 2[La(NO3)3L(H2O)] · H2O · 0.5C2H5OH have been determined by single-crystal X-ray diffraction. The La(Pic)3L crystal structure shows that the La(III) ion is coordinated with four oxygen atoms from the ligand L and six from three bidentate picrates. Furthermore, the La(Pic)3L complex units are linked by the significant intermolecular π–π interactions between coordinate picrates to form a one-dimensional (1-D) supramolecular zigzag chain. The 2[La(NO3)3L(H2O)] · H2O · 0.5C2H5OH crystal structure shows that L gives two different arrangements around La(III) ions and induces axial chirality directed by metal ions in the assembly process of the organic ligands with metal ions, each La(III) ion is coordinated with four oxygen atoms from the ligand L, six oxygen atoms from three bidentate nitrate groups and one coordinate water molecule. Furthermore, the [La(NO3)3L(H2O)] complex units are linked by the intermolecular hydrogen bonds and π–π interaction to form a three-dimensional (3-D) netlike supramolecule.

Mononuclear lanthanide complexes of the tetradentate ligand N-phenyl-2-{2′-[(phenyl-ethyl-carbamoyl)-methoxy]-biphenyl-2-yloxy}-N-ethyl-acetamide (L) with picrate and nitrate counterions have been synthesized. The anion is seen to exert a significant influence on the supramolecular structures and luminescent properties.Figure optionsDownload as PowerPoint slide