title: Structures, molecular orbitals and UV-vis spectra investigations on Br2C6H4: a computational study.
abstract: The dibromobenzenes (1,2-, 1,3- and 1,4-Br2C6H4) have been studied by theoretical methods. The structures of these species are optimized and the structural characteristics are determined by density functional theory (DFT) and the second order Møller-Plesset perturbation theory (MP2) levels. The geometrical structures of Br2C6H4 show a little distortion of benzene ring due to the substitution of highly electronegativity of bromine atoms. The electronegativity of bromine atoms in 1,4-Br2C6H4 is predicted to be more negative than 1,2- and 1,3-Br2C6H4. In addition, dipole moment and frontier molecular orbitals (FMOs) of these Br2C6H4 are performed as well. The 1,4-Br2C6H4 is slightly more reactive than 1,2- and 1,3-Br2C6H4 because of its small HOMO-LUMO energy gap. The simulated UV-vis spectra are investigated by time-dependent density functional theory (TD-DFT) approach, which are in excellent agreement with the available experimental value. Our calculations show that a few of absorption features are between 140nm and 250nm, which is in ultraviolet C range, and the red shift of 1,3- and 1,4-Br2C6H4 are predicted. Moreover, the UV absorption features of these Br2C6H4 in water or methanol are predicted to be more intense than in gas phase due to solvent effect.
authors.affiliation: Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan. tsanghsiu@gmail.com
authors.forename: Tsang-Hsiu
authors.initials: TH
authors.lastname: Wang
authors.forename: Chen-Shuo
authors.initials: CS
authors.lastname: Hsu
authors.forename: Wen-Lin
authors.initials: WL
authors.lastname: Huang
authors.forename: Yih-Hsing
authors.initials: YH
authors.lastname: Lo
mesh_terms: D000327:Adsorption; D001969:Bromobenzenes / Q000737:chemistry*; D003198:Computer Simulation; D004553:Electric Conductivity; D004583:Electrons; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D001969:Bromobenzenes
keywords: DFT; Dibromobenzene; TD-DFT; UV