Lanthanide-Organic Frameworks Constructed from 2,7-Naphthalenedisulfonate and 1H-Imidazo[4,5-f][1,10]-phenanthroline: Synthesis, Structure, and Luminescence with Near-Visible Light Excitation and Magnetic Properties.

Abstract

New Ln-metal-organic frameworks (Ln-MOFs), {[Ln(2,7-NDS)(IP)(OH)(H2O)2]·mH2O}n [Ln = Sm 1, Eu 2, Gd 3, Tb 4, Dy 5, m = 0.5-0; 2,7-NDS = 2,7-naphthalenedisulfonate, and IP = 1H-imidazo[4,5-f][1,10]-phenanthroline) were obtained by the hydrothermal method. The Ln-MOFs feature one-dimensional double chain structures. The photoluminescent properties of these complexes were investigated. Notably, the Eu-MOF exhibits a broad excitation band from 250 to 400 nm in the UV-vis region, and it presents red emission from the 5D0 → 7FJ transitions (where J = 0-4) of the Eu3+ ion. It is noteworthy that it still shows intense emission under near-visible irradiation at 350 nm < λex < 385 nm. Using the Eu-MOF as a luminescent sensor, the detection of Fe3+/Ag+ and ornidazole (ODZ)/ronidazole (RDZ) in aqueous medium was realized with long excitation wavelengths of 368 nm or even 385 nm in the near-visible region. This work provides a new approach to designing an efficient red emission with broad-band and near-visible light excitation and with luminescent chemosensor capability for biological applications. In addition, the Eu-MOF red light incorporated Gd-MOF blue-green light, and a white-light emission is realized based on a two-component Gd0.99803Eu0.00197 doped complex. Magnetic studies of the Dy-MOF reveal that it has a single-molecule magnet and slow magnetic relaxation behavior with an energy barrier Ueff of 82.39 K.