Lithium Borate-Squarate: An Organic-Inorganic Groups-Mixed Nonlinear Optical Crystal with Large Birefringence

Zhiyong Xue; Xin Wen; Yuchen Yan; Jindong Chen; Zhanggui Hu; Jiyang Wang; Ning Ye; Guang Peng

doi:10.1021/acs.inorgchem.4c05604

Lithium Borate-Squarate: An Organic-Inorganic Groups-Mixed Nonlinear Optical Crystal with Large Birefringence

Inorg Chem. 2025 Mar 3;64(8):3637-3642. doi: 10.1021/acs.inorgchem.4c05604. Epub 2025 Feb 18.

Authors

Zhiyong Xue¹, Xin Wen^{1

2}, Yuchen Yan¹, Jindong Chen¹, Zhanggui Hu¹, Jiyang Wang^{1

2}, Ning Ye¹, Guang Peng¹

Affiliations

¹ Tianjin Key Laboratory of Functional Crystal Materials, Institute of Functional Crystal, Tianjin University of Technology, Tianjin 300384, China.
² State Key Laboratory of Crystal Materials and Institute of Crystal Materials, Shandong University, Jinan 250100, China.

PMID: 39964223
DOI: 10.1021/acs.inorgchem.4c05604

Abstract

To design new nonlinear optical (NLO) crystals efficiently, mixing two or more types of functional groups is a favored strategy. Herein, by combining two types of planar π-conjugate groups, triangular (BO₃)^3- and square (C₄O₄)^2-, the new lithium borate-squarate composite NLO crystal Li₂(C₄O₄)(H₃BO₃)(H₂O)₄·H₃BO₃ was synthesized, featuring a layered structure. This crystal exhibits a moderate second harmonic generation (SHG) response of 1.1 × KDP and a large birefringence of 0.267@1064 nm. Theoretical calculations demonstrate that the synergistic effect of the two types of groups is responsible for its optical performance. This work also enriches the currently scarce borate-squarate composite compound system.