Vibrational spectroscopic and computational studies on diisopropylammonium bromide
Autor: | V. Sivasubramanian, R. M. Sarguna, T. R. Ravindran, Pattukkannu Murugavel, B.K. Das, Shradhanjali Sahoo, Ch. Thirmal, Sharat Chandra, T.N. Sairam |
---|---|
Rok vydání: | 2017 |
Předmět: |
Chemistry
Phonon Infrared spectroscopy 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Atomic and Molecular Physics and Optics 0104 chemical sciences Analytical Chemistry Crystal Crystallography symbols.namesake Phase (matter) CASTEP symbols Orthorhombic crystal system 0210 nano-technology Raman spectroscopy Instrumentation Spectroscopy Monoclinic crystal system |
Zdroj: | Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 184:211-219 |
ISSN: | 1386-1425 |
Popis: | Diisopropylammonium bromide (DIPAB) can be crystallized either in an orthorhombic (P212121) or in a monoclinic (P21) structure at room temperature depending on synthesis conditions. The non-polar orthorhombic structure exhibits a subtle, irreversible transformation into the ferroelectric monoclinic-II (m-II) phase above ~ 421 K. At a slightly higher temperature of 426 K this m-II (P21) phase reversibly transforms into a disordered, paraelectric monoclinic-I (P21/m) structure. We synthesized DIPAB in the orthorhombic structure, heated it to obtain the m-II phase and carried out a systematic study of their Raman and IR spectra. We obtained the phonon irreducible representations from factor group analysis of the orthorhombic and m-II structures based on the reported structural information. DIPAB is an organic molecular crystal, and the vibrational spectra in the intramolecular region (200–3500 cm− 1) of the two different phases are identical to each other, indicating weak inter-molecular interactions in both crystalline structures. In the low wavenumber region (10–150 cm− 1) the Raman spectra of the two phases are different due to their sensitivity to molecular environment. We also carried out first principles calculations using Gaussian 09 and CASTEP codes to analyze the vibrational frequencies. Mode assignments were facilitated by isolated molecule calculations that are also in good agreement with intramolecular vibrations, whereas CASTEP (solid state) results could explain the external modes. |
Databáze: | OpenAIRE |
Externí odkaz: |