Series of novel lanthanide complexes with a ladder-shaped 1-D double chain: Preparation, structures and photophysical properties

Abstract Series of novel lanthanide complexes [Ln(4-carboxybenzenesulfonate)(H2O)5]nnCl (Ln = Sm (1), Gd (2), Dy (3)) have been synthesized through solvothermal reactions and the structures were characterized by single-crystal X-ray diffraction. They are isostructural with a ladder-shaped one-dimensional (1-D) double chain structure. The solid-state photoluminescence measurements reveal that complexes 1 and 2 display emission bands in yellow and ultraviolet region, while complex 3 shows an upconversion emission band in the green region. These emission bands are resulted from the characteristic emissions of the 4f electron intrashell transition of the 4G5/2 → 6HJ (J = 5/2, 7/2, 9/2; Sm(III) ions in 1), 6P5/2 → 8S7/2 (Gd(III) ions in 2) and 4F9/2 → 6H13/2 (Dy(III) ions in 3). Complexes 1 and 3 possess CIE (Commission Internationale de I'Eclairage) chromaticity coordinates of (0.518, 0.4806) and (0.3318, 0.6483), respectively. The CCT (Correlated Color Temperature) are 2415 K and 5609 K for complexes 1 and 3. The solid-state UV/visible diffuse reflectance spectra reveal that complexes 1, 2 and 3 have optical band gaps of 1.5 eV, 4.6 eV and 3.3 eV, respectively.