title: Density functional theory characterisation of 4-hydroxyazobenzene.
abstract: We report the structural properties, infrared (IR) and Raman spectra, dipole moment, polarisability, hardness and chemical potential of the trans and cis configurations of 4-hydroxyazobenzene calculated using the B3LYP functionals. All calculations were performed with the following basis sets: 6-31G, 6-31++G, 6-31G(d,p), 6-31++G(d,p), 6-31G(2d,2p), 6-31++G(2d,2p) and 6-311++G(2d,2p). We observed that 6-31++G(d,p) gives similar results to 6-311++G(2d,2p). Consequently, SVWN and PW91 methods were also used in association with 6-31++G(d,p) to test the influence of the different models of exchange and correlation functionals. A planar structure was obtained for all the optimised trans configuration structures. In both isomers, the presence of the hydroxyl group leads to an asymmetry in certain structural parameters. From these results, two IR or Raman active frequencies can be used to easily distinguish trans and cis configurations. The trans configuration was found to be more stable than the cis configuration by 67 +/- 2 kJ mol(-1) at 0 K. The difference of the dipole moment between trans and cis for 4-hydroxyazobenzene was found to be lower than for trans and cis azobenzene.
authors.affiliation: Institut Supérieur des Matériaux et Mécaniques Avancés du Mans, 44 Av. Bartholdi, 72000, Le Mans, France. bminisini@ismans.fr
authors.forename: Benoit
authors.initials: B
authors.lastname: Minisini
authors.forename: Guillaume
authors.initials: G
authors.lastname: Fayet
authors.forename: François
authors.initials: F
authors.lastname: Tsobnang
authors.forename: Jean François
authors.initials: JF
authors.lastname: Bardeau
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D001554:Benzene / Q000737:chemistry*; D004583:Electrons; D008958:Models, Molecular; D008968:Molecular Conformation; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman
chemical_list: C524594:4-hydroxyazobenzene; D001391:Azo Compounds; D001554:Benzene