Lanthanide diphosphonates based on a V-shaped ligand: syntheses, structures, experimental and theoretical luminescence properties

Abstract

One series of isostructural lanthanide phosphonates, namely [Ln 2 IJH 2 L) 3 ]ij(H 2 O) 5 ] (H 4 L = (5-methyl-1,3-phenylene)bisIJphosphonic acid); Ln = Eu (1), Gd (2), Tb (3), and Dy (4)), have been successfully synthesized from a V-shaped rigid ligand. Systematic characterizations using single-crystal and powder X-ray diffraction (XRD), thermogravimetric analyses (TGA), and photoluminescence spectroscopy were accomplished. It was found that these compounds all crystallize in the cubic I2 1 3 space group, showing three-dimensional framework structures. The frameworks are stable up to 350°C and show their respective characteristic metal-centered emissions. The photoluminescence properties were also theoretically investigated by using a newly developed software program -LUMPAC. The energy transfer and back energy transfer rates were estimated, and the T 1 → 5 D 1 and T 1 → 5 D 0 channels were revealed to be the dominant pathways. The combination of experimental and theoretical studies on the photoluminescence properties substantially supports the understanding and design of highly luminescent inorganic-organic hybrid materials.

Self-Assembly Syntheses, Structural Characterization, and Luminescent Properties of Lanthanide Coordination Polymers Constructed by Three Triazole-Carboxylate Ligands

“…81 In three Tb 3+ complexes, the triplet energy level T 1 of ligand H 4 L 3 (21552 cm −1 ) is extremely close to the resonant level of Tb 3+ ion (20500 cm −1 ) in complex 13, and the energy gap (1052 cm −1 ) is too small to prevent the back energy transfer from excited state of Tb 3+ ion to triplet state of the ligand. 82,83 Therefore, a relatively lower efficiency of ligand-to-metal energy transfer takes place in complex 13, leading to a low observed luminescence quantum yield of complex 13. Likewise, it is not difficult to understand that, in the Eu 3+ complexes, the observed luminescence quantum yields of complexes 2 and 6 (10.1% and 14.3%) are higher than that of complex 11 (4.8%), since the triplet state of the ligand H 4 L 3 (21552 cm −1 ) is very close to the 5 D 2 emitting state of Eu 3+ ion (212000 cm −1 ), which offers the opportunity for the thermalassisted back energy transfer from excited state of central Eu 3+ ion in complex 11.…”

Hydrophobic species-enabled acid–base multi-catalysis for stereoselective access to renewable trans-anethole

“…The first diffraction peak of PAS-Hf (2 : 1 : 0.5) represented the formation of the interlayer by the coordination of the -PO 3 groups and Hf. 34 The 31 P MAS NMR spectrum in Fig. 1E shows the two different binding modes of phosphonates.…”

Speciation of metal phosphonates with the assistance of weak interactions

“…The synthesis of (5-methyl-1,3-phenylene)bis( phosphonic acid) (H 4 L) has been reported in our recent work. 6 Elemental analyses were performed on a Vario EL III elemental analyzer. IR spectra were recorded in the range of 4000-400 cm −1 on a Nicolet 6700 FTIR spectrometer with KBr pellets.…”

“…Our results revealed that the crystallinity of metal diphosphonates could also be improved by the introduction of one methyl group on the benzene core. With this method employed, four lanthanide 6 and six transition metal diphosphonates with a variety of structures have been obtained from H 4 L. There are not only many π⋯π interactions but also many C-H⋯O and C-H⋯π interactions in these structures, suggesting the contribution of weak interactions to the improved crystallinity.…”

“…Metal phosphonates have been of great interest in the past two decades due to their aesthetic architectures and potential applications 1,2 in the fields of optics, [3][4][5][6] magnetism, 7,8 gas adsorption/separation, 9,10 catalysis, [11][12][13] proton conductivity, [14][15][16] magnetic resonance imaging (MRI), 17 etc. The need for high performance metal phosphonates stimulates scientists to explore more compounds and the high tunability of phosphonic acid ligand makes it possible.…”