Blue Excitement: The Lanthanide(III) Chloride Oxidomolybdates(VI) Ln₃Cl₃[MoO₆] (Ln = La, Pr, and Nd) and Their Spectroscopic Properties

Abstract

The lanthanide(III) chloride oxidomolybdates-(VI) with the empirical formula Ln 3 Cl 3 [MoO 6 ] (Ln = La, Pr, and Nd) were synthesized by solid-state reactions utilizing the respective lanthanide trichloride, lanthanide sesquioxide (where available), and molybdenum trioxide together with lithium chloride as a fluxing agent. The title compounds crystallize in hexagonal space group P6 3 /m (a = 942−926 pm, c = 542−533 pm, Z = 2). Besides tetracapped trigonal prismatically coordinated Ln 3+ cations, noncondensed trigonal prismatic [MoO 6 ] 6− entities are found in the crystal structure. In addition to X-ray diffraction, the title compounds were also characterized by single-crystal Raman and infrared spectroscopy as well as measurements to determine their magnetic susceptibility and behavior at low temperatures. The most outstanding properties of the Ln 3 Cl 3 [MoO 6 ] representatives (Ln = La, Pr, and Nd), however, are of an optical nature, because their band gaps, determined by diffuse reflectance spectroscopy, show a significant shift toward lower energies compared to those of other rare-earth metal chloride molybdates with a different polyhedral arrangement. This culminates in La 3 Cl 3 [MoO 6 ]:Eu 3+ exhibiting luminescence, which can be excited in the visible range of the electromagnetic spectrum by a blue light-emitting diode.

Heteroanionic LaBrVIO4 (VI = Mo, W): Excellence in Both Nonlinear Optical Properties and Photoluminescent Properties

“…50−61 The four or six coordination environments for Mo and W atoms are the most common. Our study also confirmed that the distortion degree 22 and K 5 (W 3 O 9 F 4 ) (IO 3 ). 103 The birefringence of LaBrVIO 4 (VI = Mo and W) was estimated by both experimental measurements and DFT calculations.…”

“…The high stability and easy-to-grow large crystals of LaBrWO 4 and LaBrMoO 4 inspired us to explore more optical applications of LaBrWO 4 and LaBrMoO 4 . The closely related REClVIO 4 (RE = Y and La–Lu; VI = Mo and W) system has demonstrated excellent applications as PL materials. − In contrast to Cl-containing compounds, the rather soft bromides were probably not suitable for PL applications due to the luminescence quenching effect . In this work, good luminescence properties of LaBrWO 4 and LaBrMoO 4 were achieved via rare earth element doping (Figure ).…”

“…The IR spectrum did not show any intrinsic vibrational absorption of chemical bonds in the wavelength range of 2.5–10 μm. Strong absorption peaks appear in the range of 10–20 μm, which can be assigned to the ν­(Mo–O) or ν­(W–O) vibrations for LaBrMoO 4 and LaBrWO 4 , respectively. ,,− The IR spectrum of LaBrMoO 4 and LaBrWO 4 is comparable to many tungsten-oxides or molybdenum-oxides, such as CsNa 2 Eu 2 H 3 [Eu 2 (H 2 O) 7 (α-Si 2 W 18 O 66 )]­Cl 2 ·30H 2 O, La 3 Cl 3 [MoO 6 ], and K 5 (W 3 O 9 F 4 ) (IO 3 ) . The birefringence of LaBrVIO 4 (VI = Mo and W) was estimated by both experimental measurements and DFT calculations.…”

“…Heteroanionic compounds, which constitute two or more different anions, have attracted growing interest due to their structural flexibility and emerging physical properties, including nonlinear optical (NLO) properties, − superconducting properties, − photoluminescent response, − and thermoelectric properties, − etc. Heteroanionic compounds are different from polyanionic compounds, where there are anion–anion interactions existing within polyanionic clusters such as polyanionic [PO 4 ] 3– . ,− Heteroanionic compounds do not contain direct anion–anion interactions.…”