Coupling Narrow Band Gap and Switchable SHG Responses in a New Molecule Ferroelectric: Imidazolyl Propylamine Pentabromo Stibium(III)

Due to the existence of some cross properties such as SHG (second-harmonic generation), ferroelectricity, piezoelectricity, and thermoelectricity, molecular ferroelectrics have been widely used as a composite multipurpose material. Particularly, organic-inorganic molecular ferroelectrics have received much interest recently because of their unique flexible structures, friendly environment, ease of synthesis, etc. Also, these hybrids show great flexibility in band-gap engineering. Here we report a new molecular halide, [C6H13N3SbBr5] n (1; C6H13N3 = 1-(3-aminopropyl)imidazole), which experiences a unique ferroelectric to paraelectric phase transition at around 230 K from space group P2(1) to P2(1)/c. Significantly, compound 1 exhibits a narrow band gap with a value of 2.52 eV, large pronounced SHG-active, perfect rectangle hysteresis loops with a large spontaneous polarization of 6.86 mu C/cm(2). DSC (differential scanning calorimetry) and dielectric dependence on temperature tests and the volume change before and after the phase transition show that compound 1 is characterized by a second-order phase transition. These findings will contribute to the multifunctional materials field of organic-inorganic hybrids.

Automated summary

Molecular ferroelectrics are widely used as composite multipurpose materials due to their cross properties such as SHG, ferroelectricity, piezoelectricity, and thermoelectricity. Organic-inorganic molecular ferroelectrics have attracted much interest recently for their unique structures and band-gap engineering flexibility, showing potential for breakthroughs in multifunctional materials.