Abstract：A 2D Pr-Cd heterometal-organic compound, [Pr2Cd3(EDTA)3(H2O)11]·(H2O)14(1) (H4EDTA=ethylene diamine tetraacetic acid) has been successfully prepared by the H4EDTA ligand, Pr6O11 and CdCl2·2.5H2O. The structure of 1 was determined by X-ray single-crystal diffraction. Compound 1 crystallizes in the monoclinic space group C2, a=16.154(3) Å，b=14.863(3)Å，c=14.875(3)Å，β=115.855(3)°，V=3 214.2(9)Å3, Z=2. There are nanosized heart-like Pr6Cd6O12 wheel-clusters in the structure. The coordination geometries for the two seven-coordinated Cd2+ ions are both close to that of a monocapped trigonal prism. The Pr3+ ion is ten-coordinate and described as seriously distorted dicapped square antiprism. The completely deprotonated EDTA4- ligand link one Cd2+ and two Pr3+ ions. Four carboxylate O and two N atoms of the EDTA4- ligand are all coordinated to the Cd2+ cation and the remaining carboxylate groups connect one Pr3+ ion, respectively. The Pr3+ and Cd2+ cations are bridged by 2-O alternatively to form a Pr6Cd6O12 wheel-clusters. Each Pr6Cd6O12 is linked to six surrounding wheels by sharing Pr3+, forming a highly ordered layered network. The 2D layers are further packed in …AAA… stacking mode and the free water molecules are suspended between the layers. There are strong O—H…O hydrogen-bond interactions between water molecules and carboxylate groups, and the O…O distance ranges from 2.666 to 3.050 Å. The hydrogen-bond interactions play an important role in stabling the structure. At the same time, PXRD, TG/DSC, IR and 2D IR correlation spectroscopy, solid Luminescent spectrum and UV-Visible absorption spectrum are studied. Because there are strong O—H…O hydrogen bonds, the IR spectrum of compound 1 shows broad bands around 3 680～2 640 cm-1. The four carboxylic acid groups of EDTA4- ligand are completely deprotonated, The C=O stretching vibrations peak of carboxylate groups of compound 1 shift lower wavenumber compared to H4EDTA ligand. Compound 1 shows emission peak at 360 nm that can be assigned to LMCT transition of between Cd2+and EDTA4- when it is excited at 325 nm. Compound 1 is a potential luminescent material. 2D IR correlation spectrum of 1 indicates that the stretching vibrations of O—H are sensitive with the thermal perturbation because of strong hydrogen-bond interactions between water molecules and carboxylate groups. The UV-Visible absorption spectrum of compound 1 shows the absorption bands of n→σ* and π→π* transitions of EDTA4- ligand and f→f transition of Pr3+.
林青锋，周良良，孙燕琼，陈义平. 二维镨-镉异核金属配合物的水热合成、晶体结构及谱学性能研究[J]. 光谱学与光谱分析, 2019, 39(10): 3034-3039.
LIN Qing-feng, ZHOU Liang-liang, SUN Yan-qiong, CHEN Yi-ping. The Hydrothermal Synthesis, Crystal Structure and Spectral Properties of a 2D Pr-Cd Heterometal Complex. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019, 39(10): 3034-3039.
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