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

doi:10.3964/j.issn.1000-0593(2019)10-3034-06

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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 EDTA^4- ligand link one Cd²⁺ and two Pr³⁺ ions. Four carboxylate O and two N atoms of the EDTA^4- 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 EDTA^4- 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 EDTA^4- 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 EDTA^4- ligand and f→f transition of Pr³⁺.

Key words：Pr-Cd heterometal complex; Crystal structure; Luminescent spectrum; 2D IR correlation spectrum; UV-Visible absorption spectrum

Received: 2018-09-04 Accepted: 2019-01-28

ZTFLH:

O644.1

Corresponding Authors: SUN Yan-qiong E-mail: sunyq@fzu.edu.cn；sunyanqiong@fzu.edu.cn

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2019)10-3034-06 OR https://www.gpxygpfx.com/EN/Y2019/V39/I10/3034