Preparation, spectroscopic properties of 1,4-di ( N, N-diisopropylacetamido)-2,3(1 H,4 H)-quinoxalinedione (L) lanthanide complexes and the supramolecular structure of [Nd 2L 2(NO 3) 6(H 2O) 2]·H 2O

Abstract

The reaction of lanthanide nitrate with 1,4-di ( N, N-diisopropylacetamido)-2,3(1 H,4 H)-quinoxalinedione (L) yields six novel Ln(III) complexes ([Ln 2L 2(NO 3) 6(H 2O) 2]·H 2O) which are characterized by elemental analysis, thermogravimetric analysis (TGA), conductivity measurements, IR, electronic and 1H NMR spectroscopies. A new quinoxalinedione-based ligand is used as antenna ligand to sensitize the emission of lanthanide cations. The lowest triplet state energy level of the ligand in the nitrate complex matches better to the resonance level of Eu(III) and Sm(III) than Tb(III) and Dy(III) ion. The f–f fluorescence is induced in the Eu 3+ and Sm 3+ complexes by exciting into the π– π* absorptions of the ligand in the UV. Furthermore, the crystal structures of a novel binuclear complex [Nd 2L 2(NO 3) 6(H 2O) 2]·H 2O has been determined by single-crystal X-ray diffraction. The binuclear [Nd 2L 2(NO 3) 6(H 2O) 2]·H 2O complex units are linked by the intermolecular hydrogen bonds and π– π interactions to form a two-dimensional (2-D) layer supramolecule.