Structural Insights into Layered Tetrahalocuprates(II) Based on Small Unsaturated and Cyclic Primary Ammonium Cations.

Layered hybrid halometallates represent a promising class of multifunctional materials, yet with many open challenges regarding the interaction between building blocks. In this work, we present a synthetic and analytical methodology for the efficient synthesis and structural analysis of a series of novel tetrahalocuprate(II) hybrids based on small alkylammonium cations. Observed robustness in geometrical motifs provided a platform for crystal structure determination, even from the complex laboratory powder diffraction data. The slight differences in inorganic layer geometry and severe differences in organic bilayer packing are quantified using well-established descriptors for these materials, and dependences of geometric parameters on anion and cation choice are accounted for. Temperature dependence of structural parameters for one of the tetrachlorocuprate hybrids that was chosen as a model unveils a possible geometrical origin of thermochromism in these materials.