Manipulation of Crystal Structures and Properties by the Variation of Halides for Two Organic–Inorganic Hybrids [(C6H15ClNO)2CoX4] (X = Cl or Br)

The manipulation of structures and properties is a useful method in designing new materials. In this paper, two organic–inorganic hybrid compounds [(C6H15ClNO)2CoX4] (1, X = Cl; 2, X = Br) with reversible phase transition characteristics have been successfully synthesized. Systematic characterizations including crystal structure, thermal, dielectric, semiconducting, and photoluminescence properties were performed. Replacement of Cl with Br brings about not only the variation of the space group from C2/c to P21/c but also their properties. In comparison with Cl, the large Br atom could slow down the phase transition dynamics and give a larger thermal hysteresis of ∼25 K. Consequently, different shapes of switchable dielectric transition behavior are shown between 1 and 2. In addition, compound 2 has a smaller semiconducting band gap Eg than 1 (1.60 vs 1.65 eV). The results of this study will provide positive clues to manipulate the property of organic–inorganic hybrid compounds.