Syntheses, Crystal Structures and Characterization of Two New Lanthanide Mercury Halide Compounds

Abstract

Two new lanthanide mercury halide compounds with isonicotinic acid as a ligand, namely, [Gd(HIA)₂(IA)(H₂O)₂(HgCl₂)]_n(nHgCl₄)·3nH₂O (1) (HIA = isonicotinic acid) and {[Nd(HIA)₃(DMF)(H₂O)]_n}[(Hg₄Br₁₁)_n](2HgBr₂)(nBr)·nH₃O·0.5nH₂O (2) (DMF = N,N′-Dimethylformamide), were synthesized by means of solvothermal reactions and characterized by single-crystal X-ray diffraction. Compound 1 is characterized by a two-dimensional (2-D) layer-like structure, while compound 2 features a one-dimensional (1-D) chain-like structure. The lanthanide ions in both compounds are eight coordination and show a square antiprism geometry. The mercury ions exhibit various coordination motifs. Compound 1 shows a ultraviolet upconversion photoluminescence emission, while compound 2 displays red photoluminescence. The photoluminescence emissions come from the characteristic emissions of the 4f electron intrashell transitions of the ⁶P_7/2 → ⁸S_7/2 of the Gd³⁺ ions in compound 1 and the ⁴F_9/2 → ⁴I_9/2, ⁴F_7/2 + ⁴S_3/2→ ⁴I_9/2, ⁴F_5/2 + ²H_9/2→ ⁴I_9/2, ⁴F_3/2 → ⁴I_9/2 of the Nd³⁺ ions in compound 2. Compound 2 has CIE (Commission Internationale de I'Éclairage) chromaticity coordinates (0.7142, 0.2857) and its CCT (correlated color temperature) is 138224 K. Solid-state UV/Vis diffuse reflectance spectra discovered that their semiconductor band gaps are 3.12 eV and 3.23 eV, respectively.