Theoretical study of two-photon absorption in donor-acceptor chromophores tetraalkylammonium halide/carbon tetrabromide.
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.
Shen
Juan
J
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.
Cheng
Wen-Dan
WD
Wu
Dong-Sheng
DS
Lan
You-Zhao
YZ
Li
Fei-Fei
FF
Huang
Shu-Ping
SP
Zhang
Hao
H
Gong
Ya-Jing
YJ
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*
D006842:Hydrocarbons, Brominated; D000644:Quaternary Ammonium Compounds; C031387:carbon tetrabromide