Elucidating Structure–Property Correlation in Perovskitoid and Antiperovskite Piperidinium Manganese Chloride

In the world of semiconductors, organic–inorganic hybrid (OIH) halide perovskite is a new paradigm. Recently, a zealous effort has been made to design new lead-free perovskite-like OIH halides, such as perovskitoids and antiperovskites, for optoelectronic applications. In this context, we have synthesized a perovskitoid compound (Piperidinium)MnCl3 (compound 1) crystallizing in an orthorhombic structure with infinite one-dimensional (1D) chains of MnCl6 octahedra. Interestingly, this compound shows switchable dielectric property governed by an order–disorder structural transition. By controlling the stoichiometry of piperidine, we have synthesized an antiperovskite (Piperidinium)3Cl[MnCl4] (compound 2), the inverse analogue of a perovskite, consisting of zero-dimensional (0D) MnCl4 tetrahedra. This type of organic–inorganic hybrid antiperovskite halide is unique and scarce. Such a dissimilarity in lattice dimensionality and Mn2+ ion coordination ensues fascinating photophysical and magnetic properties. Compound 1 exhibits red emission with a photoluminescence quantum yield (PLQY) of ∼28%. On the other hand, the 0D antiperovskite compound 2 displays green emission with a higher PLQY of 54.5%, thanks to the confinement effect. In addition, the dimensionality of the compounds plays a vital role in the exchange interaction. As a result, compound 1 shows an antiferromagnetic ground state, whereas compound 2 is paramagnetic down to 1.8 K. This emerging structure–property relationship in OIH manganese halides will set the platform for designing new perovskites and antiperovskites.