6533b863fe1ef96bd12c7907

RESEARCH PRODUCT

Efficient Diffusion-Controlled Ligand Exchange Crystal Growth of Isostructural Inorganic–Organic Halogenidorhodates(III): The Missing Hexaiodidorhodate(III) Anion

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The monohydrates of piperazine-1,4-diium hexabromidorhodate(III) bromide and hexaiodidorhodate(III) iodide were obtained by a diffusion-controlled ligand exchange crystal growth method using a hydrochloric acid solution of rhodium(III) chloride trihydrate and piperazine, dissolved in hydrobromic and hydroiodic acid, respectively, separated by a layer of hydrohalic acid. Both inorganic–organic hybrids are defined by the general formula (C4H12N2)2[RhX6]X·H2O (X = Br, 1 or I, 2). They both crystallize in the orthorhombic Pnma space group, and they are isostructural with an isostructurality index above 95%. The cationic building blocks—piperazine-1,4-diium ions and the inorganic components—slightly distorted octahedral [RhX6]3– complexes, isolated X– anions and water of crystallization molecules are connected by related but different systems of interactions. The comparison of packing arrangements and interactions in the crystals of 1 and 2 with those in metal-free (C4H12N2)Br2·H2O, 3, and (C4H12N2)I2·I2, 4, clearly illustrates the occurrence and hierarchy of specific interactions: the bromide-containing structures are dominated by the O/N/C–H···X hydrogen bonds that are less pronounced or exchanged by the X···X halogen bonds in the corresponding iodide-containing structures. The structural features derived from the X-ray diffraction studies are confirmed by the solid-state IR and Raman spectroscopic results supported by the thermoanalytical analyses.