Two-step thermotropic phase transition and dielectric relaxation in 1D supramolecular lead iodide perovskite [NH@18-crown ether]PbI.

The supramolecular lead iodide perovskite crystals, {[NH(18-crown-6)]PbI} (1), (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane), was successfully achieved by a facile solvent evaporation strategy using a DMF solution containing equal molar quantities of PbI, NHI and 18-crown-6. The supramolecular perovskite was characterized by microanalysis for C, H and N elements, thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD) and single crystal X-ray diffraction techniques. DSC measurements demonstrated that 1 experiences a two-step thermotropic phase transition around 333 K and 383 K, respectively.