title: Study on the prediction of visible absorption maxima of azobenzene compounds.
abstract: The geometries of azobenzene compounds are optimized with B3LYP/6-311G* method, and analyzed with nature bond orbital, then their visible absorption maxima are calculated with TD-DFT method and ZINDO/S method respectively. The results agree well with the observed values. It was found that for the calculation of visible absorption using ZINDO/S method could rapidly yield better results by adjusting OWF(pi-pi) (the relationship between pi-pi overlap weighting factor) value than by the TD-DFT method. The method of regression showing the linear relationship between OWF(pi-pi) and BL(N-N) (nitrogen-nitrogen bond lengths) as OWF(pi-pi)=-8.1537+6.5638BL(N-N), can be explained in terms of quantum theory, and also be used for prediction of visible absorption maxima of other azobenzne dyes in the same series. This study on molecules' orbital geometry indicates that their visible absorption maxima correspond to the electron transition from HOMO (the highest occupied molecular orbital) to LUMO (the lowest unoccupied molecular orbital).
authors.affiliation: School of Materials Science and Chemical Engineering, Zhejiang University, Hangzhou 310027, China. liujunna@zju.edu.cn
authors.forename: Jun-na
authors.initials: JN
authors.lastname: Liu
authors.forename: Zhi-rong
authors.initials: ZR
authors.lastname: Chen
authors.forename: Shen-feng
authors.initials: SF
authors.lastname: Yuan
mesh_terms: D000042:Absorption; D001391:Azo Compounds / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D003198:Computer Simulation; D004579:Electron Transport / Q000528:radiation effects; D008027:Light; D008956:Models, Chemical; D008958:Models, Molecular
chemical_list: D001391:Azo Compounds; C009850:azobenzene