Two New Nonaborates with {B₉} Cluster Open-Frameworks and Short Cutoff Edges

Area of Science:

• Inorganic Chemistry
• Materials Science
• Crystal Engineering

Background:

• Borate clusters are fundamental building blocks in inorganic materials.
• Exploring novel borate structures with mixed metal cations can lead to unique properties.
• Understanding structure-property relationships is crucial for designing advanced materials.

Purpose of the Study:

• To synthesize and characterize new nonaborate compounds using mixed alkali and alkaline-earth metals.
• To investigate the structural diversity of nonaborate clusters and their assembly into extended frameworks.
• To evaluate the optical properties and potential applications of the synthesized nonaborates.

Main Methods:

• Solvothermal synthesis method.
• Single-crystal X-ray diffraction for structural determination.
• UV-Vis absorption spectroscopy for optical property analysis.

Main Results:

• Successfully synthesized two new nonaborates: Na2Ba0.5[B9O15]·H2O (1) and Na4Ca1.5[B9O16(OH)2] (2).
• Compound 1 features a 3D framework constructed from [B9O19]11- clusters and 1D chains with 10-member ring channels.
• Compound 2 exhibits a 2D layer structure built from [B9O18(OH)2]11- clusters with 14-member ring windows, forming a 3D supramolecular framework via hydrogen bonds.
• Both compounds show short cutoff edges below 190 nm with wide bandgaps (6.31 and 6.39 eV).

Conclusions:

• The solvothermal method is effective for synthesizing complex nonaborates with diverse cluster types.
• The identified nonaborate clusters and their framework assemblies are unprecedented.
• The wide bandgaps suggest promising potential for applications in deep UV optoelectronic devices.