Above room-temperature dielectric and nonlinear optical switching materials based on [(CH)S][MBr] (M = Cd, Mn and Zn).

In this paper, three zero-dimensional organic-inorganic hybrid compounds [(CH)S][CdBr] (1), [(CH)S][MnBr] (2) and [(CH)S][ZnBr] (3) were synthesized. The phase transition behavior of 1, 2 and 3 was well characterized by differential scanning calorimetry (DSC) and variable temperature single crystal diffraction measurements. The phase transition temperature of 1, 2 and 3 was at ca. 315 K in the heating process. The vigorous ordered-disordered reorientation and displacement motion of [(Me)S] and [MBr] of 1, 2 and 3 induce the structural phase transition from the centrosymmetric (CS) space group Pnma to the non-centrosymmetric (NCS) space group P222. The apparent second-harmonic generation (SHG) switching responses further confirm this CS to NCS symmetry breaking. Moreover, dielectric studies illustrate that 1, 2 and 3 display distinctly switchable dielectric behavior, revealing their potential application in dielectric switches. This finding suggests that sulfonium-based organic-inorganic hybrids can be used to build phase transition materials, broadening the way for exploring dielectric and nonlinear optical (NLO) switching materials.