Raman and infrared spectra in organic layer crystals of squaric acid

Abstract

The Raman spectra of squaric acid and its deuterated derivative are measured for temperatures from 77 to 450 K covering both ordered and disordered phases. Infrared absorption spectra are investigated for thin films of the single crystals and compared with the Raman spectra. It is found that the vibrational Davydov splitting due to the interlayer interaction is large for the external modes, while i t is small for the internal modes of the squaric molecule. This behavior is explained by the model that the interlayer interaction acts between the hydrogen bonds of adjacent layers and is localized in the region near the hydrogen bonds. The temperature dependence of the frequencies and the linewidths is discussed in relation to the phase transition mechanism.Les spectres Raman de I'acide carre et de son dkrivk deuterie ont BtB mesurks Q des tempkratures comprises entre 77 e t 450 K couvrant & la fois les phases ordonnkes e t dbsordonnkes. Les spectres d'absorption infrarouges ont Btk Btudiks sur des couches minces monocristallines e t compares avec les spectres Raman. On a constate que le dkdoublement vibrationnel de Davydov du^ a l'intkraction intercouche est large pour les modes externes, mais petit pour les modes internes de la molkcule carr6e. Ce comportement est expliquk par le modde: l'inthraction intercouche agit entre Ies liaisons hydrogene des couches adjacentes e t est localiske dans la region pres des liaisons hydrog h e . La dependance de la tempkrature, des frkquences e t des Iargeurs de raies est discutke en relation avec le mkcanisme de la transition de phase.

Growth, crystal structure, Hirshfeld surface, optical, piezoelectric, dielectric and mechanical properties of bis(L-asparaginium hydrogensquarate) single crystal

“…The bands at 2925 and 2854 cm À1 may be due to the asymmetric and symmetric stretching of the C-H bond of the l-asparagine moiety of the BASQ compound. The peaks at 1724 and 1639 cm À1 are assigned to the stretching frequency of the C O groups (Nakashima et al, 1979). The stretching vibrations of C C of the squaric acid moiety display its characteristics at 1561 cm À1 .…”

Spectroelectrochemical and Density Functional Theory Study of Squaric Acid Adsorption and Oxidation at Gold Thin Film and Single Crystal Electrodes

“…Squaric acid (or squarate anions) have also been employed for the synthesis of metal nanoparticles 14,15 , porous carbon microparticles 16 , 3D cube-shaped composites 16 and porous alumina 17 . Some experimental vibrational studies have been reported for squaric acid in the solid phase [18][19][20] , where the formation of hydrogen bonds between neighbouring squaric acid molecules gives rise to layers containing the molecular cyclic structure 4 . An experimental and theoretical study of matrix-isolated squaric acid has also been reported 21 .The vibrational properties of squaric acid and its anions have been studied theoretically, both as isolated species 22,23 and in solution 23,24 , as well as experimentally 25 .…”

“…Some experimental vibrational studies have been reported for squaric acid in the solid phase, − where the formation of hydrogen bonds between neighboring squaric acid molecules gives rise to bidimensional layers . An experimental and theoretical study of matrix-isolated squaric acid has also been reported .…”