title: Theoretical study of two-photon absorption in donor-acceptor chromophores tetraalkylammonium halide/carbon tetrabromide.
abstract: Two-photon absorption properties of a series of donor-acceptor chromophores of tetraalkylammonium halide/carbon tetrabromide ([NR4h.CBr4], h = Cl, Br, I; R = Me, Et, Pr) complexes are investigated in terms of the calculated results by the time-dependent density functional theory (TDDFT) technique combined with the sum-over-states (SOS) method. The modeling two-photon absorption spectra show that these charge-transfer complexes have large two-photon absorption (TPA) cross sections and the [NEt4I.CBr4] has the largest TPA cross section delta with the value of 5.0 x 10(-45) cm4 s photon(-1). The maximum values of delta increase with increasing separations between the donor/acceptor in the order Cl...Br < Br...Br < I...Br for [NEt4h.CBr4] complexes; however, the TPA cross sections delta vary slightly as the size of the alkyl group increases from methyl to propyl for the bromide as a donor, and the maximum wavelength of the TPA peak lambdamax indicates a bathochromic shift. The charge transfers from the halide anion to the carbon tetrabromide make a significant contribution to the excited states, and the donor-acceptor charge transfer plays an important role in the TPA activity, whereas changes in size of alkyl group do not make a substantial contribution to TPA.
authors.affiliation: State Key Laboratory of Structual Chemistry, Fujian Institute of Research on the Structure of Matter, the Chinese Academy of Sciences, Fuzhou, Fujian 350002, People's Republic of China.
authors.forename: Juan
authors.initials: J
authors.lastname: Shen
authors.forename: Wen-Dan
authors.initials: WD
authors.lastname: Cheng
authors.forename: Dong-Sheng
authors.initials: DS
authors.lastname: Wu
authors.forename: You-Zhao
authors.initials: YZ
authors.lastname: Lan
authors.forename: Fei-Fei
authors.initials: FF
authors.lastname: Li
authors.forename: Shu-Ping
authors.initials: SP
authors.lastname: Huang
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Ya-Jing
authors.initials: YJ
authors.lastname: Gong
mesh_terms: D003198:Computer Simulation; D006842:Hydrocarbons, Brominated / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D017785:Photons; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*
chemical_list: D006842:Hydrocarbons, Brominated; D000644:Quaternary Ammonium Compounds; C031387:carbon tetrabromide