Theoretical Studies on the First Hyperpolarizabilities of One-dimensional Donor-bridge-acceptor Chromophores

【摘要】 The ground-state dipole moments and second-order nonlinear optical (NLO) pro- perties of a series of one-dimensional (1D) chromophores with donor-bridge-acceptor (D-B-A) structures have been investigated by using the second-order Mller-Plesset (MP2) and density functional theory (DFT) methods with the basis set of 6-31+G(d). According to the calculated results, the relationship between the molecular static first hyperpolarizability (βμ) and the directions of electron transition has been summarized. In terms of the sign of βμ, these 1D organic chromophores were classified into two categories: type I with negative βμ and type II bearing positive βμ. The analyses show that the remarkable difference of the first hyperpolarizabilities between ? and II chromophores is associated mainly with the electrostatic interaction between terminal groups and the transport electrons in excited states. Moreover, different from the popular viewpoint, the obtained results also show that most of this series of 1D D-B-A molecules are more charge-separated in the ground states than in the excited states. As a whole, this theoretical investigation, to some extent, can be considered as a useful reference in designing the NLO chromophores with large first hyperpolarizabilities.更多还原

【Abstract】 The ground-state dipole moments and second-order nonlinear optical (NLO) pro- perties of a series of one-dimensional (1D) chromophores with donor-bridge-acceptor (D-B-A) structures have been investigated by using the second-order Mller-Plesset (MP2) and density functional theory (DFT) methods with the basis set of 6-31+G(d). According to the calculated results, the relationship between the molecular static first hyperpolarizability (βμ) and the directions of electron transition has been summarized. In terms of the sign of βμ, these 1D organic chromophores were classified into two categories: type I with negative βμ and type II bearing positive βμ. The analyses show that the remarkable difference of the first hyperpolarizabilities between ? and II chromophores is associated mainly with the electrostatic interaction between terminal groups and the transport electrons in excited states. Moreover, different from the popular viewpoint, the obtained results also show that most of this series of 1D D-B-A molecules are more charge-separated in the ground states than in the excited states. As a whole, this theoretical investigation, to some extent, can be considered as a useful reference in designing the NLO chromophores with large first hyperpolarizabilities.更多还原