Vibrational spectroscopic, optical and thermal properties of a hybride pyridazine perchlorate complex-An experimental and theoretical study

Various methods of experiment: differential scanning calorimetry (DSC), differential thermal analysis (DTA), thermogravimetric analysis (TGA) and infrared (IR) spectroscopy have been used to investigate the phase transitions in pyridazine perchlorate crystal. DSC showed the existence of phase transition at T = 341 K. The vibrational IR spectra in Nujol and Perfluorolube mulls were studied in a wide temperature range, from room temperature to 380 K. Special attention was put on the temperatures near the phase transition temperature. The temperature changes of wavenumbers, gravity center and band intensities were analyzed to clarify the phase transition molecular mechanism. Information about hydrogen bonds was obtained. For more detailed band assignment and overall spectral presentation Raman and far infrared (FT-FIR) spectra at room temperature have been carried out. The experimental data interpretation was supported by theoretical calculations based on density functional theory, with the B3LYP method and 6-311++G(d,p) basic set. Some theoretical conformations were analyzed. Calculated normal vibrational modes of the molecule, their frequencies and intensities were compared with these recorded in experiment.