A Lead Mixed Halide with Three Different Coordinated Anions and Strong Second-Harmonic Generation Response.

Nonlinear optical (NLO) crystals are widely applied in information technology, micro-manufacturing and medical treatment. Herein, a new lead mixed halide with strong second-harmonic generation (SHG) response, Cs3 Pb2 (CH3 COO)2 Br3 I2 , has been designed and rationally synthesized. Cs3 Pb2 (CH3 COO)2 Br3 I2 represents the rare NLO crystal featuring that three different anions (I- , Br- and O2- ) simultaneously coordinate the Pb(II) atom to form a severely distorted [PbBr2 I2 O2 ] polyhedron with a large polarizability. Remarkably, Cs3 Pb2 (CH3 COO)2 Br3 I2 not only exhibits a very strong phase-matching SHG response of 9×KH2 PO4 (KDP), but also possesses a large birefringence (0.27@1064 nm) and high laser damage threshold (LDT). The strong SHG effect of Cs3 Pb2 (CH3 COO)2 Br3 I2 mainly originates from the oriented arrangement of [Pb2 Br3 I2 ] chains. This study points out an effective strategy to develop new NLO crystals with strong SHG response.