Phase stability and dynamics of hybrid organic–inorganic crystals [(CH3)3PH][SbCl4] and [(CH3)3PH][SbBr4]: a computational and NMR approach

Abstract

New compounds [(CH₃)₃PH][SbBr₄] and [(CH₃)₃PH][SbCl₄] adopting a discrete (0D) and one-dimensional (1D) structure, respectively, were synthesized. Differential scanning calorimetry and thermogravimetric measurements showed that both salts undergo a single phase transition at 373 K/416 K (chlorine/bromine analog) followed by partial decomposition. Both crystals were structurally characterized at room temperature. ¹H NMR measurements were used to study the dynamics of the [(CH₃)₃PH]⁺ cation in the solid phase, which helped to understand the thermal instability of the crystals. In addition, DFT (Density Functional Theory) calculations gave insight into the relative stability of the possible phases of the studied crystals. The mechanism of crystal decomposition is discussed in this work.