(CH5N3S)2Pb5Br10 and (CH5N3S)Pb2Br4: Two Nonlinear Optical Lead Thiosemicarbazide Bromides with Diverse Pb-Centered Building Units

It is of great significance to explore new nonlinear optical (NLO) materials for the development of modern laser testing technology. In this paper, two non-centrosymmetric organic-inorganic hybrid Pb-based bromides, (CH5N3S)2Pb5Br10 and (CH5N3S)Pb2Br4, were synthesized by a simple hydrothermal method. They crystallize in the Fdd2 and P212121 space groups, respectively. Both (CH5N3S)2Pb5Br10 and (CH5N3S)Pb2Br4 are three-dimensional structures formed by interconnecting Pb5(CH5N3S)2Br12 or Pb4(CH5N3S)4Br9 units. Notably, the structure units of PbBr3S, Pb2Br7, Pb2Br5N2S2, and PbBr3NS appear for the first time in thiourea compounds. (CH5N3S)2Pb5Br10 exhibits 0.6 times the second harmonic generation (SHG) effect of KH2PO4. After changing the coordination of organic and inorganic parts, (CH5N3S)Pb2Br4 shows the SHG effect of 1.02 times that of KH2PO4. Analysis of structures, NLO properties, thermal analyses, and theoretical calculations are presented in this work.