Nonlinear Optical Switching Driven by the Lone Pair Electron Effect in a Hybrid Compound: (1S, 4S)-(+)-2-Aza-5-oxabicyclo[2.2.1] heptane)2[SbCl5]

In order to take advantage of hybrid materials in their structural diversity and richness of their photoelectric properties, the research in polar materials has been extended to metal-organic compounds in recent years. The main synthesis strategy is to use the molecular dynamics. Here, we describe that the second harmonic generation (SHG) switching effect can be effectively achieved by combination of coordination distortion of metal ions with s² electrons and molecular dynamics. We synthesized a noncentrosymmetric complex, (1S,4S)-(+)-2-aza-5-oxabicyclo[2.2.1]heptane)₂[SbCl₅], and found that it undergoes an isomorphic phase transition at 382 K. Accompanying the phase transition, the SHG experiences a switching process, and its strength changes from 0.2 times of that of KDP to only noise level. Systematic characterization reveals that the significant change of coordination distortion of the Sb³⁺ and the change of thermal motion of organic cations lead to the SHG switching effect. This finding shows that the combination of lone pair electron effect of metal ion and molecular dynamics characteristics would be a feasible strategy in development of polar hybrid materials.