Luminescence Modulation, White Light Emission, and Energy Transfer in a Family of Lanthanide Metal–Organic Frameworks Based on a Planar π-Conjugated Ligand

Abstract

Three isostructural lanthanide metal–organic frameworks (Ln-MOFs), {[Ln2(BDPO)1.5(DMA)3(H2O)]·5H2O } n (1-Ln, Ln = Eu, Gd, and Tb) were constructed by a less-investigated large delocalized π-electron conjugated ligand N,N′-bis­(3,5-dicarboxyphenyl)-oxalamide (H4BDPO). 1-Ln reveals unprecedented trinodal (4,4,6)-connected networks based on binuclear cluster units and planar BDPO linkers. Density functional theory (DFT) and time dependent-DFT calculations were performed on the ground and excited states to provide insight into geometries, the frontier molecular orbitals, and singlet and triplet state energies of H4BDPO ligand. 1-Eu and 1-Tb exhibit strong typical red and green emission of Eu3+ and Tb3+ ions, respectively, originating from the highly efficient energy transfer from BDPO to metal centers, as demonstrated by the comparison of triplet excited energies of ligands and metal ions. Importantly, by doping different concentrations of Eu3+ and Tb3+ ions, a series of dichromatic doped 1-Eu x Tb 1‑x MOFs were fabricated, showing an unusual fluent change of luminescent color among green, yellow, orange, and red. Meanwhile, the trimetallic doped 1-Eu 0.0855 Gd 0.6285 Tb 0.2860 emits white light, with the correlated color temperature of 5129 K as well as an absolute quantum yield of 22.4%.

Fluorene‐based Lanthanide Coordination Polymer: Structure, Luminescence and Sensing of Picric Acid

“…The Tb 3+ ions are coordinated by seven oxygen atoms from five L 2− ligands and one H 2 O molecule and one DMF molecule for Tb1, and five L 2− ligands and one and a half DMF, and half a H 2 O for Tb2, forming the distorted pentagonal bipyramid coordination geometry. The Tb‐O bond lengths range from 2.258(5) to 2.65(3) Å, which are comparable to those reported for other Tb‐O donor complexes . The L 2− ligands adopt the μ 3 and μ 4 bridging modes, respectively, with a carboxylate oxygen atom coordinating to a metal ion.…”

Luminescent and magnetic bifunctional coordination complex based on a chiral tartaric acid derivative and europium

“…Apart from their excellent magnetic properties, most Ln-CPs also display characteristic sharp and narrow luminescence emissions originating from f-f transitions of the Ln 3+ ions, featuring excellent colour purity, long fluorescence lifetimes and high quantum yields (Roy et al, 2014;Xu et al, 2017;Zhang et al, 2017). Owing to the prominent optical and magnetic properties of Ln-CPs, it is of great importance and an enormous challenge to build dual optical-magneto materials based on lanthanide ions (Li et al, 2015(Li et al, , 2017a which have potential applications in luminescent sensing, magnetic resonance imaging (MRI), cryogenic magnetic refrigeration, high-density information storage and quantum computations (Khalfaoui et al, 2017;Li et al, 2015;Liu et al, 2014;Zhao et al, 2015).…”

Conversion from Heterometallic to Homometallic Metal–Organic Frameworks

“…Lanthanide–organic frameworks (LOFs) containing lanthanide ions in the metal nodes can be useful for directly sensing metal‐ion exchange in the metal nodes . This is because the photoluminescence (PL) intensity of LOFs decreases as the PL lanthanide ions in the metal nodes are removed from LOFs upon their exchange with other optically different metal ions. However, LOFs containing lanthanide ions in the metal nodes are rarely explored despite their potential for directly sensing metal‐ion exchange in the metal nodes.…”