Emergent Chirality and Nonlinear Optical Switching in a Ferroelastic Molecular Perovskite Solid Solution

Solid solution has long been used in inorganic oxides to modulate structures and physical properties. In contrast, for molecular solid solutions, new and unexpected properties can emerge because of the distinct molecular conformations and spatial orientations. Herein, for the first time, we obtained a three-dimensional molecular perovskite ferroelastic [(EPCF)x(EPCCl)1–x][Mn(dca)3] solid solution (EPCF = [Et3P(CH2)2F]+, EPCCl = [Et3P(CH2)2Cl]+, and dca = dicyanamide, 0 ≤ x ≤ 1). At x = 0.170–0.405, the mixing of the centrosymmetric [EPCCl][Mn(dca)3] (P21/c) and [EPCF][Mn(dca)3] (C2/c) phases generates a new chiral P212121 phase with a second harmonic generation (SHG) response. Such a finding is unprecedented but desirable for tuning the crystal structure from centrosymmetry to noncentrosymmetry. The combination of the prominent SHG effect, increased spontaneous strain, and long-range magnetic ordering at a higher temperature opens a new avenue for constructing multifunctional molecular materials.