Structural phase transitions and dielectric transitions in a 1,4-diazabicyclo[2.2.2]octane (dabco) based organic crystal

Crystal structure of 1-methyl-1,4-diazabicyclo[2.2.2]octan-1-ium poly[aqua-bis(μ2-perchlorato-κ3O,O′:O′′)sodium], C7H17Cl2N2NaO9

C7H17Cl2N2NaO9, orthorhombic, Pbca (no. 61), a = 13.907(3) Å, b = 10.927(2) Å, c = 19.194(4) Å, V = 2916.8(10) Å3, Z = 8, Rgt(F) = 0.0472, wRref(F2) = 0.1129, T = 298 K.

Crystal Structure and Phase Transition of the C–H···F–H-Bonded Supramolecular Compound with 4-Nitroanilinium Based on 18-Crown-6

A novel inorganic-organic hybrid supramolecular macrocyclic compound, (4-nitroanilinium)(18-crown-6)(PF6)(1), was synthesized and characterized by infrared spectroscopy, thermogravimetric analysis, elemental analysis, differential scanning calorimetry (DSC), and single-crystal X-ray diffraction. Crystal 1 is found to comprise 1D C–H···F–P hydrogen-bonded chains of (4-nitroanilinium+)(18-crown-6) supramolecular cations and PF6− anions. DSC measurements confirm that 1 undergoes a reversible phase transition at 255 K with a hysteresis width of 6 K. A strong dielectric response is observed above 250 K at a low frequency (500 Hz), suggesting the occurrence of proton transfer in the C–H···F–P hydrogen bonds. A precise analysis on the main packing and structural differences, as well as the changes in the intermolecular interaction between the low- and high-temperature phases, reveals that C–H···F–P hydrogen bonds are the main factors affecting phase transition and dielectric behavior.

Role of crystallization water molecules on hydrogen-bonded structures and dielectric phase transitions in amino trimethylene phosphonic acid-based crystals

Amino trimethylene phosphonic acid-based organic salts show crystallization water molecule-triggered dielectric transitions and relaxations.