Synthesis, characterization and disorder-order phase transition of inorganic-organic hybrid materials (H2dabco-CH2-Cl)[M||Cl4] (M = Co, Zn)

Two inorganic-organic hybrid compounds, (H(2)dabco-CH2-Cl)[MIICl4] (M = Co, Zn; H2dabco-CH2-Cl = 1-chloromethyl-1,4-diazabicyclo.2.2.2] octan-1,4-diium cation), were synthesized under slow evaporation conditions. DSC measurements indicated that compounds (H(2)dabco-CH2-Cl)[MIICl4] (M = Co, Zn) underwent reversible phase transitions at 355 K and 358 K with hysteresis widths of 4 K and 5 K, respectively. Temperature-dependent dielectric measurements also confirmed the phase transitions. Variabletemperature X-ray diffraction data demonstrated that the phase transition was from a high-temperature phase with the space group Pnma to a low-temperature phase with the space group P2(1)/c. The disorderorder transformation of the terminal Cl atom of the (H(2)dabco-CH2-Cl)(2+) cation triggered by the decrease in temperature may drive the phase transition.