Theoretical modeling of infrared spectra of benzoic acid and its deuterated derivative

Terahertz Time-domain Spectra of Aromatic Carboxylic Acids Incorporated in Nano-sized Pores of Mesoporous Silicate

“…The Raman bands of the three acids in SBA-16 were clearly observed as well as those of the crystal samples. The frequency values of the observed bands of ophthalic acid, 2 benzoic acid, 5 and salicylic acid 6 corresponded well with the theoretical calculations.…”

“…Characteristic peaks were clearly observed with the crystal samples at ∼2.1 THz (∼70 cm -1 ); however, such peaks were not detectable with the samples in SBA-16 even at low temperature. According to a previous report on the theoretical modeling of infrared spectra of benzoic acid dimer, the infrared active band at 63 cm -1 is assigned as the cogwheel mode, 5 that is, a vibration of the cyclic hydrogen-bonded frame consists of two molecules interfaced by a hydrogen-bond interaction. Thus, it is natural for this mode to be inactivated by the incorporation of the molecules into the nano-sized pores of SBA-16 due to the separation of the dimer.…”

“…The results indicate that incorporating the molecules in the nano-sized pores of SBA-16 slightly changes the molecular structures, and that the molecules incorporated in SBA-16 interact with silanol groups (Si-OH) on the SBA-16 surface. 18 It is noteworthy that the 420 cm -1 band of the crystal benzoic acid (shown with a dotted line) which is assigned as a stretching mode of an intermolecular O ·O bond interfaced by a hydrogen-bond interaction, 5 was not detected in the SBA-16 spectra. This also supports our idea that incorporating the molecules in nano-sized spaces in SBA-16 is effective in reducing the effect of the intermolecular hydrogen bonds.…”

“…1 For example, carboxylic acids, such as o-phthalic acid, 2,3 benzoic acid, [3][4][5] salicylic acid 3,6 and their derivatives, 7 have been well studied by using mid-infrared and Raman spectroscopy combined with theoretical calculations. Over recent years terahertz time-domain spectroscopy (THz-TDS) has been demonstrated to be a powerful analytical tool to study low frequency vibrational modes and weak molecular interactions such as hydrogen bonds in the 0.1 -3.0 THz (3 -100 cm -1 ) region, corresponding to the lower end of the far-infrared (FIR) region.…”

Theoretical Studies of Dynamic Interactions in Excited States of Hydrogen-Bonded Systems

“…Benzoic acid has been also studied in the ground state by traditional spectroscopic techniques. Infrared spectra of hydrogen-bonded benzoic acid crystals have been recorded and interpreted theoretically by Flakus et al [25][26][27][28][29] and more recently by Boczar et al [30] The present work constitutes a development of this study and is also a continuation of our recent spectroscopic and theoretical studies of vibrational spectra of hydrogenbonded 1-methylthymine [31], acetic acid [32], and salicylic acid [33]. Theoretical studies on different hydrogen-bonded chemical and biochemical systems in excited electronic states have been performed in recent years [34][35][36][37].…”