title: A complete vibrational study on a potential environmental toxicant agent, the 3,3',4,4'-tetrachloroazobenzene combining the FTIR, FTRaman, UV-Visible and NMR spectroscopies with DFT calculations.
abstract: In this study 3,3',4,4'-tetrachloroazobenzene (TCAB) was prepared and then characterized by infrared, Raman, multidimensional nuclear magnetic resonance (NMR) and ultraviolet-visible spectroscopies. The density functional theory (DFT) together with the 6-31G(*) and 6-311++G(**) basis sets were used to study the structures and vibrational properties of the two cis and trans isomers of TCAB. The harmonic vibrational wavenumbers for the optimized geometries were calculated at the same theory levels. A complete assignment of all the observed bands in the vibrational spectra of TCAB was performed combining the DFT calculations with the scaled quantum mechanical force field (SQMFF) methodology. The molecular electrostatic potentials, atomic charges, bond orders and frontier orbitals for the two isomers of TCAB were compared and analyzed. The comparison of the theoretical ultraviolet-visible spectrum with the corresponding experimental demonstrates a good concordance while the calculated (1)H and (13)C chemicals shifts are in good conformity with the corresponding experimental NMR spectra of TCAB in solution. The npp(*) transitions for both forms were studied by natural bond orbital (NBO) while the topological properties were calculated by employing Bader's Atoms in the Molecules (AIM) theory. This study shows that the cis and trans isomers exhibit different structural and vibrational properties and absorption bands.
authors.affiliation: Cátedra de Química General, Instituto de Química Inorgánica, Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, Ayacucho 471, 4000 San Miguel de Tucumán, Tucumán, Argentina.
authors.forename: María V
authors.initials: MV
authors.lastname: Castillo
authors.affiliation: Instituto de Química Rosario (CONICET-UNR), Facultad de Ciencias Bioquímicas y Farmacéuticas, Suipacha 531, 2000 Rosario, Santa Fé, Argentina.
authors.forename: Jorgelina L
authors.initials: JL
authors.lastname: Pergomet
authors.affiliation: Instituto de Química Rosario (CONICET-UNR), Facultad de Ciencias Bioquímicas y Farmacéuticas, Suipacha 531, 2000 Rosario, Santa Fé, Argentina.
authors.forename: Gustavo A
authors.initials: GA
authors.lastname: Carnavale
authors.affiliation: Instituto de Investigaciones para la Industria Química (INIQUI, CONICET), Universidad Nacional de Salta, Av. Bolivia 5150, 4400 Salta, Argentina.
authors.forename: Lilian
authors.initials: L
authors.lastname: Davies
authors.affiliation: Instituto de Química Rosario (CONICET-UNR), Facultad de Ciencias Bioquímicas y Farmacéuticas, Suipacha 531, 2000 Rosario, Santa Fé, Argentina.
authors.forename: Juan
authors.initials: J
authors.lastname: Zinczuk
authors.affiliation: Cátedra de Química General, Instituto de Química Inorgánica, Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, Ayacucho 471, 4000 San Miguel de Tucumán, Tucumán, Argentina. Electronic address: sbrandan@fbqf.unt.edu.ar.
authors.forename: Silvia A
authors.initials: SA
authors.lastname: Brandán
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D002722:Chlorobenzenes / Q000737:chemistry*; D004785:Environmental Pollutants / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman
chemical_list: D001391:Azo Compounds; D002722:Chlorobenzenes; D004785:Environmental Pollutants; C013279:3,4,3',4'-tetrachloroazobenzene
keywords: 3,3′,4,4′-Tetrachloroazobenzene; DFT calculations; Force field; Molecular structure; Vibrational spectra