Some characterizations of a new metal–organic framework (n-C₁₄H₂₉NH₃)₂CdCl₄ and the role of hydrogen bonding

ABSTRACT

A cadmium-based organic–inorganic hybrid (n-C₁₄H₂₉NH₃)₂CdCl₄ is synthesized and characterized, thermally and dielectrically. The differential scanning calorimetery (DSC) and the differential thermal analysis (DTA) thermograms were performed in a suitable range of temperature. The general feature of each thermogram indicates that the hybrid undergoes two structural phase transitions at T_major ≈ 351.5 K and T_minor ≈ 344.66 K in addition to an intermediate temperature which is located at ≈346.8 K. For further confirmation of the observed phase transitions, the complex dielectric permittivity ε* (ω,T) = ε′(ω,T) – iε″(ω,T) and ac conductivity σ_ac(ω,T) were accurately measured in the wide range of temperature 100 K<T<400 K at some suitable range of frequencies. The data evidenced the existence of such transitions. Comparison with other hybrids reveals the absence of the odd–even effect whereas the transition temperature increases with the increase of the chain length. The mechanism of proton transfer and kink defects was outlined.

KEYWORDS:

• Metal–organic framework (MOF)
• hydrogen bonds
• organic–inorganic hybrid
• ac conductivity and dielectric permittivity
• (n-C₁₄H₂₉NH₃)₂CdCl₄