Perovskites, a class of compounds that share the structure type of CaTiO₃, are notable for their structural and chemical adaptability, making them ideal functional materials for a variety of device applications. However, to meet the demand for materials in dielectric and multiferroic applications new modifications to the perovskite structure must be developed to allow for targeted synthesis of materials with these properties. In one such modification perovskites can include a thiocyanate (SCN^-) molecular linker instead of an oxide or halide anion. These thiocyanate compounds gain increased flexibility due to the thiocyanate’s multiple bonding modes and interactions with an organic cation, which stabilize structures and incorporate elements not seen in traditional perovskites. Previous work has demonstrated that these characteristics make them well suited to be dielectrics, multiferroics, optoelectronics, or magnets. However, the dearth of realized compounds in this family makes the targeted synthesis of materials for specific device applications difficult. Therefore, to move forward in developing application centered materials based on this hybrid structure it is necessary to first expand the existing chemical space of realized thiocyanate-linked hybrid compounds.
To this end, we have synthesized a new family of hybrid organic-inorganic materials with the general formula A₂Cd(SCN)₂X₂(A= CH₃NH₃⁺, (CH₃)₂NH₂⁺, CH₃CH₂NH₃⁺, CH₃(CH₂)₂NH₃⁺, X= Cl^-, Br^-). The new mixed thiocyanate-halide compounds demonstrate a novel bonding motif and represent an entirely new structure type not previously seen. The materials have been prepared via facile solid-state techniques and single crystals can be grown using solution-based methods. These hybrid materials incorporate mixed halide and thiocyanate anions to overcome problems with stability and demonstrate the validity of the proposed structural and chemical variations available. The new structure type also demonstrates the importance of hydrogen bonding in controlling the structure of molecular-linked compounds, an important structure directing effect that has not been previously explored in similar materials. By understanding the structure and properties of this family of hybrid thiocyanate materials, new compounds can now be targeted for synthesis that would be ideal functional materials for dielectric, multiferroic, and optoelectronic applications.

Patrick Woodward

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