Engineered Integration of Diverse Functional Units Induces Multifunctionality in Malonate-Borate Hybrids

Abstract

Borate-based hybrids offer an excellent platform for advanced materials design, yet integrating multiple functional units remains challenged by competing structural requirements. Here, we presented a rationally designed hybrid system that first achieves synergistic coupling between π-conjugated malonate and polymerized boro-oxygen units through precise coordination chemistry control. We synthesized eight new malonate-borate hybrids comprising two structural types: series I ([B₃O₇(OH)]-based) and series II ([H₃BO₃]-based). Starting from three centrosymmetric series I compounds, controlled variation of stoichiometry and reaction pathways yielded four non-centrosymmetric series II hybrids and one centrosymmetric series II phase, enabling tailored structural symmetry. The series II system exhibits diverse functional properties across the material series, including a high birefringence (Δn = 0.203@546 nm) with a short cutoff edge of 200 nm, strong second-harmonic generation responses rivaling KH₂PO₄ (KDP), and high ionic conductivity. This work establishes a new paradigm for functional crystal engineering by elucidating fundamental design principles for balancing competing property requirements through controlled structural evolution.

Keywords

birefringence / borates / ionic conductors / SHG / UV multifunctional optoelectronic crystals

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2025 The Author(s). Aggregate published by SCUT, AIEI, and John Wiley & Sons Australia, Ltd.