APb2(C7H3NO4)2I (A = K, Rb, Cs): rare stable nonlinear optical crystals with second-harmonic generation response and highly distorted lead core coordination polyhedra

Abstract

The development of nonlinear optical (NLO) crystals with excellent performance has been the goal of numerous researchers. Herein, iodide has been successfully introduced into lead 2,6-pyridinedicarboxylates to rationally synthesize a series of new stable NLO crystals, APb₂(C₇H₃NO₄)₂I (A = K, Rb, Cs), via a mild mix-solvothermal method. It is interesting to note that APb₂(C₇H₃NO₄)₂I (A = K, Rb, Cs) has a 3D noncentrosymmetric cubic framework composed of highly distorted [PbNO₅] and [PbNO₄I] coordination polyhedra. Remarkably, KPb₂(C₇H₃NO₄)₂I exhibits a strong second-harmonic generation (SHG) response about 3.4 times that of KDP and a high thermal stability above 300 °C under an air atmosphere. This work provides an effective strategy for the further exploration of high-performance NLO crystals.