Two alkali metal borates built by {Li@B₁₄} and {B₁₅} cluster units

Area of Science:

• Inorganic Chemistry
• Materials Science
• Solid-State Chemistry

Background:

• Alkali metal borates are a diverse class of compounds with tunable properties.
• Hydrothermal synthesis offers a versatile route for creating complex inorganic structures.
• The exploration of novel boron clusters is crucial for advancing materials science.

Purpose of the Study:

• To synthesize and characterize new alkali metal borates.
• To investigate the structural features of novel boron clusters.
• To evaluate the potential of these compounds for optical applications.

Main Methods:

• Mid-temperature hydrothermal synthesis was employed.
• Single-crystal X-ray diffraction was used for structural determination.
• UV-Vis spectroscopy and birefringence measurements were conducted.

Main Results:

• Two novel alkali metal borates, K7[{Li@B12O18(OH)4}{BO(OH)3}2] (1) and LiNa2K2[B15O25] (2), were successfully synthesized.
• Compound 1 features a first-time reported Li-centered {Li@B14} cluster with a unique [B12O18(OH)6] core.
• Compound 2 exhibits a 3D open-framework based on a B15O29 cluster, templated by multiple alkali metal ions.

Conclusions:

• The successful synthesis of these compounds expands the family of alkali metal borates.
• The novel boron clusters demonstrate the versatility of boron chemistry.
• Both compounds possess UV cut-off edges and moderate birefringence, suggesting suitability for UV optical devices.