Synthesis, structure and near-infrared photoluminescence of hexanitratoneodymate ionic liquids

Five hexanitratoneodymate-based rare earth complexes (1-5) were synthesized using a straightforward method. Purple plate crystals of 1 were isolated and the crystal structure was determined by single-crystal X-ray diffraction with respect to the coordination mode of the nitrate anion to the central Nd(III) ion. (1: monoclinic system P2(1)/c, a = 15.9460(3) angstrom, b = 10.2457(6) angstrom, c = 33.323(3) angstrom, beta = 91.8108(17)degrees, V = 3109.11(11) angstrom(3), Z = 4). The central Nd(III) ion is surrounded by six bidentate nitrate ligands, with a major trend towards high symmetry of the [Nd(NO3)(6)](3-) anion as an icosahedron. Thermal properties were determined from differential scanning calorimetry (DSC) combined with thermogravimetric analysis (TGA) tests. Complexes 3-5 are found to be room temperature liquids, and their excitation and emission spectra were recorded. These complexes exhibit intense near-infrared (NIR) luminescence emission, which originates from interconfigurational f-f transitions F-4(3/2) -> I-4(J) multiplet (J = 9/2-13/2). These liquid Nd(III) complexes are of interest as potential NIR luminescent soft materials with high thermal stability.