Two Mixed Alkali-Metal Borates Templated from Cations to Clusters.

Area of Science:

• Inorganic Chemistry
• Materials Science
• Solid-State Chemistry

Background:

• Mixed alkali-metal borates are explored for their diverse structural motifs and potential applications.
• The B₆O₁₃^8- cluster is a versatile structural building unit in borate chemistry.
• Solvothermal synthesis offers a controlled environment for crystal growth and discovery of novel materials.

Purpose of the Study:

• To synthesize and characterize new mixed alkali-metal borates.
• To investigate the structural diversity arising from different templating agents within the same synthetic system.
• To evaluate the nonlinear optical properties of the synthesized materials, particularly for deep-ultraviolet applications.

Main Methods:

• Solvothermal synthesis was employed to prepare the target compounds.
• Single-crystal X-ray diffraction was used to determine the crystal structures of the two borates.
• Second harmonic generation (SHG) measurements and UV-Vis spectroscopy were performed to assess optical properties.

Main Results:

• Two mixed alkali-metal borates, K_0.5Li[B₆O₁₀]·0.5H₃O (1) and [(μ₅-OH)@(Na₄Li)]_0.5[B₆O₁₀]·0.5B(OH)₃ (2), were successfully synthesized.
• Compound 1 features a centric 3D oxoboron framework, while compound 2 exhibits an acentric 3D framework interpenetrated by a 2D network, templated by unique alkali-metal clusters and borate groups.
• Compound 2 demonstrated a significant second harmonic generation response (2.8 times KDP) and a cutoff edge below 190 nm, indicating potential as a deep-UV NLO material.

Conclusions:

• The templating effect of alkali-metal clusters significantly influences the resulting borate framework structures.
• Compound 2 represents a promising new material for deep-ultraviolet nonlinear optical applications.
• This study highlights the rich structural chemistry of borates and their potential for advanced optical functionalities.