Chinese team invents new family of metallic compounds

Each compound exhibits unique properties desirable for next-generation technologies.
Loukia Papadopoulos
The nano-wheel-like metallic clusters.jpg
The nano-wheel-like metallic clusters.

Polyoxometalates, Tsinghua University Press 

A multi-institute research team based in China has fabricated a novel family of metallic compounds, each of which exhibit unique properties desirable for next-generation technologies.

This is according to a press release by the team published on Sunday.

“Polymetallic complexes are of great interest not only for their appealing molecular structure but also for their versatile applications in various fields,” said study co-corresponding author Yan-Zhen Zheng, professor in the Frontier Institute of Science and Technology (FIST) at Xi’an Jiaotong University. 

These new complexes have the potential to imbue materials with specific properties. These unique and exciting properties include the ability to fluoresce, or glow, and magnetic quirks that allow drastic temperature changes and control. 

The researchers engineered the novel polymetallic complexes with lanthanide elements, a group of 15 metallic materials also known as rare earth elements. They made use of europium, terbium and gadolinium. 

“Among all polymetallic complexes, lanthanide-based compounds have drawn unprecedented attention due to their interesting magnetic and luminescence behaviors,” Zheng said. “Several such compounds have been successfully isolated, but direct synthesis has been a challenge.”

Geometrically diverse 

It should be noted that the complexes are made of geometrically diverse components, requiring significant coordination.   

“Previous findings revealed that controlling the hydrolysis — breaking down a compound with water — of lanthanide metal ions in the presence of appropriate organic ligands would be a powerful strategy to obtain desired species,” Zheng said. 

Ligands have the unique ability to stabilize the structure of the complexes because they bond to a metal atom. As such, the researchers used hydrolysis to breakdown lanthanides in a bath containing a ligand called tricine to help stabilize the resulting clusters. 

“Through the simple hydrolysis reaction, we synthesized three lanthanide nano-clusters, and used X-ray diffraction analyses to reveal their stable, wheel-like structure,” Zheng said. “Owing to the presence of different lanthanide metal ions in these analogues, each compound shows distinctive properties.” 

The end result was a europium-based cluster that fluoresced red emissions and a terbium-based cluster that fluoresced green emissions. There was also a gadolinium-based cluster that exhibited potential applications in magnetic cooling.

Now, the research group is continuing to investigate the many potential applications of the variety of clusters, according to the statement. The study is published in the journal Polyoxometalates. 

Study abstract:

A family of polyoxo(alkoxo)lanthanide cluster {Ln15} (Ln = Eu (1), Gd (2), Tb (3)) was successfully isolated via a simple hydrolysis reaction of lanthanide metal ions in the presence of tricine ligands. X-ray diffraction analyses revealed that {Ln15} displayed a wheel-like structure with a µ5-chloride anion as a template. Interestingly, each analog showed distinctive functions based on the different Ln(III) ions. Complexes 1 and 3 in the solid state emitted the characteristic fluorescence of Eu(III) or Tb(III). The fluorescence lifetimes of the 5D0 excited state for 1 and the 5D4 excited state for 3 were tested, and the values were 890 and 250 μs, respectively. Meanwhile, gadolinium analog 2 exhibited a magneto-caloric effect at ultralow temperatures with a maximum −ΔSm value of 29.9 J·kg−1·K−1 at 3 K and 7 T.