The guanidine and benzoic acid (1:1) complex. The polarized vibrational studies and theoretical investigations.

The structure of guanidinium benzoate was discovered by Silva et al. On the basis of these X-ray crystallographic studies the detailed DFT investigation are performed. According to this result the infrared spectrum for one theoretical molecule was calculated. On the basis of potential energy distribution (PED) analysis the clear-cut assignments of observed bands were performed. For the calculated molecule with energy minimum the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) were obtained. The energy difference between HOMO and LUMO was analyzed. According to theoretical calculations the direction of dipole moments (TDM) for bands observed in infrared spectra are analyzed. Verification of theoretical TDM behaviors is performed on the basis of experimental polarized specular reflection infrared spectra. The detailed assignments of observed bands is presented. Both theoretical and experimental spectra are compared. Crucial role of three different hydrogen bonds is studied in detail. Additionally, on the basis of differential scanning calorimetric study no phase transition was found in investigated crystal in the range 100-400K.

Guanidinium perchlorate ferroelectric crystal. Study of vibrational properties based on experimental measurements and theoretical calculations.

The infrared and Raman spectra of guanidinium perchlorate were measured at room temperature. The spectra are discussed with the framework of literature X-ray structure in relation to internal hydrogen bond network. For complete vibrational analysis the theoretical calculation of both infrared and Raman spectra in DFT approach were performed. The clear-cut assignment of observed bands was made on the basis of PED analysis. On the basis of theoretical studies the electrostatic charges and energies of HOMO and LUMO orbitals were obtained. Additionally the first order hyperpolarizability of investigated molecule was calculated. The obtained results are in good agreement with literature data, but according to performed calculation the specific damping of ß hyperpolarizability in unit cell (comparable with isolated molecule) is observed. To explain in detail phase transitions phenomena (at ca. 452 and 454K) described in literature the temperature dependent infrared powder spectra were recorded. The temperature dependencies of bands position and intensities for titled crystal in the range 11-480K are analyzed.

Crystal structure, differential scanning calorimetric, infrared spectroscopy and theoretical studies of C(NH2)2(NH)*CH2=CHCOOH noncentrosymmetric crystal.

The X-ray and vibrational spectroscopic analysis of a new molecular complex of guanidine and acrylic acid are reported. The crystal of C(NH(2))(2)(NH)(*)CH(2)=CHCOOH belongs to Pna2(1) space group of orthorhombic system with Z=4, a=9.9242(34) Å, b, c=8.3951(14) Å. In the crystal structure the macroscopic symmetry center is absent. The differential scanning calorimetric (DSC) experiment of powder sample indicates on continuous phase transition at 235.8K. The room temperature infrared spectrum of guanidine*acrylic acid powder sample has been measured. The spectrum is discussed on the basis of crystallographic data. The IR spectra for the powder sample were also measured at low temperatures (12-300 K). The temperature relationships of band position for obtained spectra are analyzed. Additionally, the results of theoretical calculation of vibrational spectra, equilibrium structure, HOMO, LUMO and first order hyperpolarizability are presented.