FTIR, FTRaman, UV–Visible and NMR spectroscopic studies on 3,3′,4,4′-tetrachloroazoxybenzene, an azoxybenzene derivative with toxic effects

CASTILLO, MARÍA V.; PERGOMET, JORGELINA L.; CARNAVALE, GUSTAVO A.; DAVIES, LILIAN; ZINCZUK, JUAN; BRANDÁN, SILVIA ANTONIA

JOURNAL OF MOLECULAR STRUCTURE

ELSEVIER SCIENCE BV

Año: 2017 vol. 1142 p. 18 - 27

0022-2860

We have synthesized 3,3′,4,4′ Tetrachloroazoxybenzene (TCAOB) and, later, characterized it by using infrared, Raman,1H, 13C NMR and UV?visible spectroscopies. The structural, topological and vibrational properties of four Cis and threeTrans isomers were theoretically predicted by using the hybrid B3LYP together with the 6-31G* and 6-311++G** basissets. The 69 normal modes of vibration for all TCAOB isomers were assigned by using the scaled quantum mechanicalforce field (SQMFF) procedure and their experimental vibrational spectra and normal internal coordinates. The highstabilities of all Cis and Trans isomers are supported by the π→π*, n→σ*, n→π* and π*→π* electronic transitions calculatedby NBO studies while the AIM analyses reveal for the Trans forms the existence of intra-molecular C H⋯Ohydrogen bonds, as suggested by the broad IR band observed in the higher wavenumbers region. The low gap energyfor the Trans I isomer supports their higher reactivity probably due to the repulsion of the more electronegative Cl andO atoms as a consequence of their proximities. In addition, the force constants for all Cis and Trans isomers were calculatedby using both levels of theory. Here, the comparisons of the predicted IR, Raman, NMR and ultraviolet?visiblespectra with the corresponding experimental ones demonstrate good concordances. The existence of the N O groups inall TCAOB isomers support the differences in their properties, as compa