AuCd4: A Hume–Rothery Phase with VEC of 1.8 and Icosahedral and Trigonal-Prismatic Clusters as Building Blocks

Structure and stability of γ1-AuZn2.1: a γ-brass-related complex phase in the Au-Zn System

γ₁-AuZn_2.1 in the Au-Zn binary system has been synthesized and its structure analyzed by single-crystal X-ray diffraction. It crystallizes in the trigonal space group P31m (No. 157) with ∼227 atoms per unit cell and represents a \surd3a × \surd3a × c superstructure of rhombohedrally distorted γ-Au_5-xZn_8+y. The structure is largely tetrahedrally closed packed. The formation of γ₁-AuZn_2.1 can be understood within the framework of a Hume-Rothery stabilization mechanism with a valence electron concentration of 1.68 e/a (valence electrons per atom).

Effective luminescence sensing of Fe3+, Cr2O72-, MnO4- and 4-nitrophenol by lanthanide metal-organic frameworks with a new topology type

Lanthanide MOFs (Ln-MOFs), {[Ln₂(L)₂(H₂O)₂]·5H₂O·6DMAC}_n, [Ln^||| = Eu(1) and Tb(2); H₃L = 4,4'-(((5-carboxy-1,3-phenylene)bis(azanediyl))bis(carbonyl)) dibenzoic acid, DMAC = N,N'-dimethylacetamide], with a new topology type have been isolated. Single crystal X-ray diffraction indicates that complexes 1 and 2 are isostructural with binuclear [Eu₂(COO)₇]_n secondary building units as 7-connected nodes and H₃L ligands as 3-connected nodes and can be viewed as a (5,7)-connected 3D framework with a new topological point symbol of {3²·4⁴·5⁴} {3⁴·4⁶·5⁶·6⁵}. Complexes 1 and 2 exhibit an excellent luminescence sensing response to inorganic ions Fe³⁺, Cr₂O₇^2-, MnO₄^- and 4-nitrophenol, with a low detection limit and high K_sv value. Interestingly, when the MnO₄^- ions are detected, the color of the solid sample is observed to change from yellow to brown, visually indicating luminescence induction, which makes the process of detecting MnO₄^- ions simpler and more practical. Moreover, by using time-resolved photoluminescence techniques, complex 1 can effectively eliminate background fluorescence interference during detection and improve detection accuracy. Solvent luminescence studies, pH stability and PXRD data indicate that complexes 1 and 2 can be used as excellent water-stable multi-response luminescent sensors for detecting a wide variety of toxic substances. In addition, the mechanism of selective detection is explained by the energy competition between the excitation of complexes 1 and 2 and the ultraviolet absorption of the responsive substance.

A water-stable lanthanide coordination polymer as a multiresponsive luminescent sensor for Fe3+, Cr(vi) and 4-nitrophenol

Constructing water stable lanthanide coordination polymers (Ln-CPs) is of great importance for practical applications in biological and environmental areas and necessary for systematic research on the relationship between the properties of Ln-CPs and structures of linker ligands. A two-dimensional (2D) Eu coordination polymer (Eu-CP) {[Eu(L)(HCOO)]·H2O}n (H2L = isomer of 5-((pyridin-3-yloxy)methyl)isophthalic acid) is synthesized by the reaction of Eu(NO3)3·6H2O and H2L and heating at 140 °C. Single crystal X-ray diffraction analysis indicates that the Eu-CP presents a 2D network structure formed by binuclear metal clusters and bridged linkers COO- and HCOO-. The luminescence properties of the Eu-CP are explored at room temperature in the solid-state. The Eu-CP emits bright and stable red light due to the antenna effect from the ligand to the metal ion. The characteristic emission peaks of Eu3+ can be observed in its spectra. The luminescence intensity of the Eu-CP can be sensitively quenched by inorganic ions Fe3+, CrO42-, and Cr2O72- and the organic molecule 4-nitrophenol (4-NP). The Eu-CP can be a multiresponsive luminescent sensor in the water phase. Solvent luminescence investigation and PXRD data demonstrate that the Eu-CP exhibits excellent water stability. Therefore, all the sensing experiments are carried out in the water system. This multi-responsive luminescent sensor can detect Fe3+, Cr(vi) or 4-NP with high sensitivity and low detection limits in aqueous solution. Furthermore, the mechanism for the selective sensing of Fe3+, Cr(vi) or 4-NP is also explored which can mainly be explained by energy competition between the absorption of the analytes and the excitation of the Eu-CP.

RhCd9+δ (−1.18≤δ≤0.29) a γ-brass related cubic giant cell structure

The compound RhCd9+δ (−1.18≤δ≤0.29) has been synthesized and the average structure has been analyzed by single crystal X-ray diffraction. The average structure crystallizes in the face centered cubic space group F4̅3m (216) and contains ~405 atoms/unit cell. It represents a (2aγ)3-superstructure of cubic γ-brass and is isostructural to Rh7−xMg44+x. The comparison between the structures of RhCd9+δ and Rh7−xMg44+x has been presented using a layer description. The structure of the title phase has also been described by a “cluster” concept. The electronic structure of RhCd9+δ (−1.18≤δ≤0.29) shows that the phase is stabilized by a Hume-Rothery mechanism.