[C(NH<sub>2</sub>)<sub>3</sub>]Y(HCOO)<sub>4</sub>: Constructing 3D Framework for Guanidine-Based UV Nonlinear Optical Crystals with Good Performance
Jiayin Tang, Xin Wen, Huili Zhang, Yuchen Yan, Jindong Chen, Shihui Ma, Min Luo, Chensheng Lin, Ning Ye, Guang Peng
Abstract
The guanidine group, [C(NH 2 ) 3 ] +, is a promising π-conjugated unit for nonlinear optical (NLO) materials. However, its saturated amino coordination typically leads to weak hydrogen bond interaction and zero-dimensional structures, limiting the stability and mechanical strength. Herein, we propose a design strategy that constructs a non-centrosymmetric (NCS) three-dimensional (3D) framework for [C(NH 2 ) 3 ] + by utilizing (HCOO) − and rare-earth cations and successfully synthesizes a novel 3D guanidine-based compound, [C(NH 2 ) 3 ]Y(HCOO) 4, which not only effectively immobilizes the [C(NH 2 ) 3 ] + but also induces an NCS arrangement. This crystal exhibits a strong second-harmonic generation response of 1.7 × KH 2 PO 4, a short UV cutoff edge of 236 nm, an appropriate birefringence of 0.099@546 nm, and good thermal stability, fulfilling critical requirements for UV NLO applications. This work provides a new strategy for developing high-performance guanidine-based UV NLO materials.