二维电荷转移结构轮烯衍生物光学性质理论研究

The relationships study of structure-nonlinear optical property of two-dimensional charge transfer molecules substituted annulenes

以一系列轮烯衍生物为目标分子,运用MP2和TD-DFT方法在6-31G(d)基组水平上计算了分子一阶超极化率β和紫外吸收光谱,研究了分子结构和非线性光学性能的关系.研究发现,本文中的二维电荷转移(2DCT)分子2—6均具有较大的β值,且紫外吸收光谱最大吸收峰和相对应的一维电荷转移(1DCT)分子8和9相比发生蓝移,这对解决"非线性效率-透光性的矛盾"给予了很大启示.对于2DCT分子2—7,分子一阶超极化率的大小和分子构型关系密切,随着键长交替(BLA)的增加,分子的β值不断减小.此外,和传统的1DCT分子不同,2DCT分子前线轨道能级差ΔEHL和β值之间无明显的变化关系,分子的最大吸收峰并不来自于HOMO到LUMO的跃迁,而是源于更深层的轨道跃迁.

The molecular first hyperpolarizabilities β and ultraviolet spectra of two-dimensional charge transfer （2DCT） substituted annulenes by employing MP2 and TD-DFT approach,respectively. It is found that these 2DCT molecules 2— 6 possess larger β values and blue-shifted absorption spectra in comparison with 1DCT molecules 8 and 9. It is helpful to solve the nonlinearity-transparency trade-off. For 2DCT molecules 2—7,values of β depend on the band length alternation （BLA） and when the BLA increases,the values of β decrease. Moreover,there is not a relationship between β and HOMO-LUMO energy gap ΔEHL for 2DCT molecules. The maximum absorption wavelength λmax of 2DCT molecules originates from deeper energy level orbital transition than HOMO→LUMO transition.