(±)-2-Methyl­piperazin-1-ium perchlorate

In the title compound, C5H13N2 +·ClO4 −, the monoprotonated piperazine ring adopts a chair conformation. In the crystal structure, cations and anions are linked by inter­molecular N—H⋯O and N—H⋯N hydrogen bonds into layers parallel to (01)

4-(N-Propan-2-ylcarbamo­yl)pyridinium perchlorate

In the title compound, C9H13N2O+·ClO4 −, the dihedral angle between the planes of the amide group and the pyridinium fragment is 34.11 (14)°. In the crystal, the cations are connected by N—H⋯O hydrogen bonds between the amide groups into chains extended along the a axis. Hydrogen bonds between the pyridinium N—H group and the perchlorate anions organize the chains into a two-dimensional network

4-Ethyl­anilinium 2-carb­oxy­acetate

In the crystal structure of the title compound, C8H12N+·C3H3O4 −, the hydrogen malonate anions are linked into infinite chains parallel to the b axis by inter­molecular O—H⋯O hydrogen bonds of the type COO−⋯HO2C in a head-to-tail fashion. The 4-ethyl­anilinium cations link adjacent anion chains by inter­molecular N—H⋯O hydrogen bonds into a two-dimensional network parallel to the b and c axes

2-Amino­pyrimidinium nitrate

In the title compound, C4H6N3 +·NO3 −, the cation is coplanar with the anion (r.m.s. deviation = 0.048 Å), and links to the anion via an N—H⋯O hydrogen bond, forming an ion pair. In the crystal, adjacent ion pairs are further linked by N—H⋯O hydrogen bonds into linear chains running along the b axis

Dielectric Properties of NaNH4\text{}_{4}SO4\text{}_{4}·2H2\text{}_{2}O-NaNH4\text{}_{4}SeO4\text{}_{4}·2H2\text{}_{2}O Mixed Crystals Mixed Crystals

The mixed crystals of NaNH$\text{}_{4}$SO$\text{}_{4}$·2H$\text{}_{2}$O-NaNH$\text{}_{4}$SeO$\text{}_{4}$·2H$\text{}_{2}$O were grown and their properties were investigated. Dielectric and differential thermal analysis studies allowed us to construct the phase diagram of the system with molar fraction, x, of NaNH$\text{}_{4}$SeO$\text{}_{4}$·2H$\text{}_{2}$O as a parameter. Nonlinear dependence of T$\text{}_{c}$ versus composition was found

Vibrational Spectroscopic Properties of a [C(NH 2

Tetraguanidinium dichloride-sulphate crystal, $[C(NH_2)_3]_4Cl_2SO_4$, abbreviated as $G_4Cl_2SO_4$ was investigated. The vibrational infrared spectra of powdered $G_4Cl_2SO_4$ crystal in Nujol mull were studied in the wide range of temperature, from 298 K to 377 K. This temperature range contains all the phases in the crystal (named III, II, I on heating, respectively). The temperature changes of wavenumbers, centre of gravity, and intensity of the bands were analyzed to clarify the molecular mechanism of the phase transitions. It was shown that in cooling from 377 K to 313 K the phase II is the same as the room temperature phase. Information about hydrogen bonds was obtained. The time dependence of internal vibrations at 356 K was observed and it was connected with slow transition III → II. For more detailed band assignment Raman spectrum at room temperature, at ferroelectric phase was carried out. Theoretical calculations were made based on density functional theory, with the B3LYP method using 6-311 + G(d,p) basic set. Calculated normal vibrational modes of the molecule, their frequencies and intensities were compared with these recorded in experiment. Theoretical description of the molecule including hydrogen bonds were optimized and the bond parameters were obtained. The Mulliken charges population analysis was performed

On the Structural Phase Transition in a Perovskite-Type Diaminopropanetetrachlorocuprate(II) NH₃(CH₂)₃NH₃CuCl₄ Crystal

Chemical preparation, differential scanning calorimetry and thermal stability differential thermal gravimetry studies, positron annihilation lifetime investigations, optical observations as well as electric properties of the NH₃(CH₂)₃NH₃CuCl₄ crystal are presented. On the basis of the differential scanning calorimetry response the structural phase transition of the first order was observed at 436 K. The enthalpy and entropy of the phase transition are equal to 1120 J/mol and 2.57 J/(mol K), respectively. Differential thermal analysis and thermogravimetric analysis studies confirmed the phase transition at 436 K and one can conclude the chemical and thermal stability of the compound up to about 480 K. Optical observations showed a continuous change of colour from yellow to dark brown above the phase transition to 436 K. Dielectric measurements showed a significant increase of conductivity upon approaching the phase transition regions, with a significant increase above the phase transition temperature. An activation energy dependent on the temperature range, and different for each particular phase, is obtained from measurements of complex impedance