Acetate-Decorated Tri-Ln(III)-Containing Antimonotungstates with a Tetrahedral {WO₄} Group as a Structure-Directing Template and Their Luminescence Properties

Abstract

Four acetate-decorated tri-Ln-substituted trimeric antimonotungstates (AMTs) Na 17 {(WO 4 )[Ln(H 2 O)(Ac)(B-α-SbW 9 O 31 (OH) 2 )] 3 }•50H 2 O [Ln = Eu 3+ (1), Dy 3+ (2), Ho 3+ (3), or Gd 3+ (4)] were isolated by reaction of Na 9 [B-α-SbW 9 O 33 ]• 19.5H 2 O, Na 2 WO 4 •2H 2 O, and Ln(NO 3 )•6H 2 O in a HAc/NaAc buffer solution. Interestingly, a tetrahedral {WO 4 } group plays a significant structure-directing template role in the formation of their polyoxoanions. With regard to luminescence properties, with a change in the excitation wavelength, it is available to switch emission colors from orange to red for 1, blue to green for 2, and blue to yellow for 3. Under the O → W LMCT excitation, energy transfer from AMT fragments to Eu 3+ , Dy 3+ , and Ho 3+ ions occurs because Ln 3+ ions can absorb energy from O → W LMCT emission of AMT segments. The temperature-dependent luminescence behaviors (25−720 °C) of 1 together with auxiliary emitting photographs illustrate that the growing emission in the temperature range of 25−100 °C results from the loss of lattice water molecules, the decline of emission between 100 and 320 °C may occur because crystals become amorphous powders, the slow emission decay (220−320 °C) is due to the case that the emission enhancement derived from the removal of water ligands on Eu 3+ ions in some degree compensates for the decline of emission intensity, the sharp decrease in emission (320−520 °C) may result from the change in the coordinate environment of Eu 3+ ions, and the weak recovery of emission (620−720 °C) may be ascribed to the formation of new phase Na 0.5 Eu 0.5 WO 4 . This work lays a significant foundation for preparing novel POM-based luminescent materials.

Facile Fabrication of Luminescent Eu(III) Functionalized HOF Hydrogel Film with Multifunctionailities: Quinolones Fluorescent Sensor and Anticounterfeiting Platform

“…If the luminescence intensity of ED 5 D 0 → 7 F 2 transition is much higher than that of MD 5 D 0 → 7 F 1 transition, then Eu 3+ centers inhibit a symmetry microenvironment. [ 19 ] Here the ratio calculation of I ( 5 D 0 → 7 F 2 )/ I ( 5 D 0 → 7 F 1 ) is 0.747, suggesting a high‐symmetry microenvironment of Eu 3+ ions. Notably, after turning off the UV lamp, MA‐IPA powders, MA‐IPA@SA hydrogel and 1 give birth to apparent blue‐green long afterglow, through monitoring the T 1 →S 0 emission at 488 nm, the fitting result of their long afterglow lifetime are τ = 1.97, 1.92, and 1.99 s severally (Figure 2b, Figure S4c,d, and Table S1, Supporting Information), which is very close to that of MA‐IPA reported by Huang.…”

“…The excitation spectrum of 1 gives a wide excitation band in the range of 300–350 nm assigned to S 0 →S n transition, five excitation peaks at 318, 360, 376, 394, 416, and 464 nm originating from 7 F 0 → 5 D 4 , 5 L 7 , 5 L 6 , 5 D 3 , and 5 D 2 transition (Figure S5a, Supporting Information). [ 19 ] The presence of excitation band of S 0 →S n transition suggests that there is a slight ET process from MA‐IPA to Eu 3+ ions. The wide phosphorescence emission band locates centered at 488 nm (Figure S5b, Supporting Information).…”

Three Lanthanide-Functionalized Antimonotungstate Clusters with a {Sb4O4Ln3(H2O)8} Core: Syntheses, Structures, and Properties

“…It is well-known that Ln-based compounds, with the merits of a narrow emission line as well as high color purity, are endowed with broad application prospects in light-emitting diodes, biosensing technologies, imaging techniques, and waveguide amplifiers. − It can be clearly observed that the emission spectrum of 1 upon 388 nm excitation (Figure a) displays four characteristic emission bands caused by Dy 3+ f–f transitions, where two strong emission bands centered at 480 and 575 nm are attributed to the magnetic dipole transition ( 4 F 9/2 → 6 H 15/2 ) and the electric dipole transition ( 4 F 9/2 → 6 H 13/2 ); the other two weak emission bands are centered at 662 nm ( 4 F 9/2 → 6 H 11/2 ) and 749 nm ( 4 F 9/2 → 6 H 9/2 ). , The intensity of the F 9/2 → 6 H 13/2 transition is higher than that of the 4 F 9/2 → 6 H 15/2 transition, indicating that Dy 3+ ions in 1 occupy the lattice site without inversion symmetry. , An excitation band of O → W ligand-to-metal-charge transfer (LMCT) and five distinct peaks at 270, 353, 367, 388, 430, and 453 nm appearing in the excitation spectrum of 1 (Figure S10a) are assigned to the 1 A 1g → 1 T 1u transition of AT ligands and 6 H 15/2 to 6 P 7/2 , 6 P 5/2 , 4 I 13/2 , 4 G 11/2 , and 4 I 15/2 transitions of Dy 3+ ions. , The lifetime decay profile of 1 (monitoring upon 574 nm emission) (Figure b) fits well using a second-order exponential equation, resulting in lifetimes of τ 1 = 2.53 μs (29.93%) and τ 2 = 14.80 μs (70.07%), and the average vaule (τ*) is 11.13 μs, similar to results from a previous report . Compound 2 emits orange luminescence upon 454 nm excitation, and three featured emission peaks located at 551, 581, and 660 nm appear in the range 540–750 nm (Figure c) and are, respectively, ascribed to Ho 3+ 5 F 4 + 5 S 2 → 5 I 8 , 5 G 6 + 5 F 1 → 5 I 7 , and 5 F 5 → 5 I 8 transitions.…”

“…50,51 The intensity of the F 9/2 → 6 H 13/2 transition is higher than that of the 4 F 9/2 → 6 H 15/2 transition, indicating that Dy 3+ ions in 1 occupy the lattice site without inversion symmetry. 52,53 An excitation band of O → W ligand-to-metal-charge transfer (LMCT) and five distinct peaks at 270, 353, 367, 388, 430, and 453 nm appearing in the excitation spectrum of 1 (Figure S10a) are assigned to the 1 A 1g → 1 T 1u transition of AT ligands and 6 H 15/2 to 6 P 7/2 , 6 P 5/2 , 4 I 13/2 , 4 G 11/2 , and 4 I 15/2 transitions of Dy 3+ ions. 54,55 The lifetime decay profile of 1 (monitoring upon 574 nm emission) (Figure 3b) fits well using a secondorder exponential equation, resulting in lifetimes of τ 1 = 2.53 μs (29.93%) and τ 2 = 14.80 μs (70.07%), and the average vaule (τ*) is 11.13 μs, similar to results from a previous report.…”

Giant Ln 30 -Cluster-Embedded Polyoxotungstate Nanoclusters with Exceptional Proton-Conducting and Luminescent Properties

“…As shown in Figure 4e and 4f, the temperature-dependent luminescence spectra of 1Eu were collected in the ranges of 77 -300 K and 298 -493 K, which reveal that its fluorescence intensity only slightly decreases by 0.02% per K on increasing temperature from 77 K to RT, but decreases drastically by 4.77% per K from RT to 493 K. Generally, luminescence intensity of reported Ln-containing POMs decreases significantly with increasing temperature. [42][43][44] While, the luminescence intensity of 1Eu is almost undisturbed in the temperature ranges of 77 -300 K, which might be attributed to its high structural stability and crystallinity that can effectively suppress the nonradiative energy loss when the temperature varies in the low temperature range, [43][44][45] and thus also exhibits different temperature-dependence luminescence performances below RT and above RT.…”