Effect of Halogenation on the Optical, Electrical, and Thermal Properties of the Model Compound [Me(i-Pr)N][SnBr].

Organic-inorganic hybrid lead halides have been extensively studied due to their outstanding physical properties and diverse compositional elements. However, environmentally benign tin-based hybrids with remarkable flexibility in bandgap engineering have been less investigated. Herein, we report the successful design and synthesis of three tin-based organic-inorganic hybrid compounds through precise molecular modification: [Me(i-Pr)N][SnBr] (), [MeCHCl(i-Pr)N][SnBr] (), and [MeCHBr(i-Pr-Br)N][SnBr] (). Building on the prototype compound , the introduction of heavier halogen atoms in (Cl) and (Br) increased the potential energy barrier required for cationic flipping, thereby achieving a rise in the phase transition temperature from 335 K () to 355 K () and 375 K (), which also perfectly coincides with the switchable dielectric anomalies and second harmonic generation (SHG) properties. Based on the two-dimensional fingerprint analysis of the Hirshfeld surface, with the introduction of halogens, the intermolecular interactions, including not only C-H···Br-Sn but also C-X···Br-Sn (X = Cl, Br) halogen···halogen interaction, lead to the higher phase transition temperatures in and . Furthermore, UV-NIR-vis absorption spectra revealed that the optical bandgap varies with the substitution from H to Cl to Br, yet all belong to direct bandgap semiconductors. Based on the aforementioned properties, this work provides an effective molecular design strategy for exploring and constructing tin switchable materials with temperature-adjustable characteristics.