Polarized Infrared and Raman Spectra and Ab-initio Calculations of Benzotriazole

Abstract

The i.r. spectra of benzotriazole have been measured from 4000 to 60 cm-1: polarized spectra of single crystals have been also obtained. The Raman spectra of polycrystalline samples and solutions have been investigated. The structural parameters and vibrational frequencies have been detennined from ab-inirio Hartree-Fock gradient calculations using the 6-31G* basis set. A detailed assignment of most of the observed bands has been proposed on the basis of the i.r. dichroism, Raman polarization data and frequency calculations.

Surface-enhanced Raman scattering (SERS) of benzotriazole derivative corrosion inhibitor prepared in aqueous media

“…In the case of BTAH and other similar benzene derivatives, one expects several modes of mixed nature: CC, NN and CN stretchings, CCC and CCH bending and also combinations. 26,43,44 In our opinion, spectra of pure BTAH and DBTO completely fit the previously cited explanations of other authors. On the other hand, cases of BTAH complexes and the products of DBTO complexing are not that simple because a Fermi resonance probably takes place in the region 1100-1200 cm 1 .…”

“…This is probably the reason why the expected SERS using 514.5 nm excitation was not observed, contrary to the results of Rubin et al 43 The spectral region of ¾650-1000 cm 1 is characterized by one of the most intensive bands appearing at ¾780 cm 1 in all studied samples. Owing to its intensity, the polarization properties observed in the case of BTAH solution 44 and agreement with the normal mode frequency calculated in the same paper, this band was also assigned to the in-plane skeletal deformation. It may be added that band position and intensity are only weakly dependent on the benzene ring substituent (the difference between BTAH and DBTO is negligible) and on molecular surroundings (whether Cu acts in the complex or as a substrate).…”

“…Our assignment is supported by the observed sharp and very intense bands in pure triazole in the vapour phase 45 and by the calculated value for BTAH from Ref. 44.…”

“…Such a pair was observed in many spectra of monoand disubstituted benzene derivatives and we assigned them as modes 1 and 12 in Wilson's notation. There is probably only a difference in terminology between this paper and the assignment used by Bigotto et al 44 At higher wavenumbers 1050-1150 cm 1 one can observe quadruplet-like features for BTAH and DBTO that are very similar in shape and whose relative intensity changes on transition from Cu complexes to thin films. Other authors 25,43,44 observe these bands at nearly the same positions for BTAH but assignments given by various groups are not unique.…”

“…Details from all recorded spectra, such as band positions and intensities, are given in Table 2. The vibration assignment for specific benzene vibrations 42 in terms of Wilson's notation and/or including a single internal coordinate was supported by experience 5,26,42,43,45 or by vibration calculation 44 obtained on BTAH or similar substances by other authors. Raman bands for chemically similar species observed in this work were put in correspondence with common assignment on the basis of local spectral similarities.…”