给体位置和数目对四苯基乙烯衍生物双光子吸收性质的影响

Effects of donor position and number on two-photon absorption properties of tetraphenylethylene derivatives

在杂化密度泛函水平上,利用响应函数方法,计算了一类四苯基乙烯衍生物的双光子吸收性质.考虑了四苯基乙烯上给电子基团的位置和数目对双光子吸收性质的影响.并且,根据实验者采用的分子,通过增加分子的平面性和共轭长度,以及增强给体强度,理论设计了三种分子结构,并计算了它们的双光子吸收性质.结果表明,给体位置和数目对双光子吸收性质有重要影响.位于分子末端的给体取代基能有效提高双光子吸收强度.随着给体数目的增加,双光子吸收波长发生红移.在四苯基乙烯的不同侧位上添加给体取代基对双光子吸收性质的影响有明显差异.与实验者采用的分子相比,理论设计的分子结构双光子吸收截面均明显增大.当三苯胺基代替四苯基乙烯基之后,双光子吸收峰发生较大红移,双光子吸收截面明显增大.

Organic materials with strong two-photon absorption response and aggregation induced emission have aroused a great deal of interest in recent years, for their many potential applications such as two-photon fluorescence microscopy, up-conversion laser, photodynamic therapy, etc. The tetraphenylethylene units are usually employed in two-photon absorption and aggregation induced emission materials because of their good electron-donating capability and special propeller starburst structures. Theoretical study on the relationship between molecular structure and two-photon absorption property is of great importance for guiding the experimental design and synthesis of functional materials. In this paper, the two-photon absorption properties of a series of organic molecules containing tetraphenylethylene and cyano groups are studied by employing the density functional response theory in combination with the polarizable continuum model. The molecular geometries are optimized at a hybrid B3LYP level with 6-31g(d, p) basis set in the Gaussian 16 program. The two-photon absorption cross sections are calculated by response theory through using the CAM-B3LYP functional with 6-31g(d) basis set in the Dalton program. The effect of donor position and number on twophoton absorption properties are investigated. In addition, by increasing the planarity and conjugated length of the molecule, as well as by enhancing the strength of the electron donor, we design three molecular structures and calculate their two-photon absorption properties. The results show that the donor position and number have important effects on two-photon absorption properties. The methoxy donor at the end of the molecule can increase the two-photon absorption intensity effectively. As the number of substituents increases, the position of the two-photon absorption peak is red-shifted. The effects of adding electron donor groups on different side positions have a significant difference in the two-photon absorption property. Comparing with the experimental molecules, the two-photon absorption cross sections of the designed molecules are greatly enhanced. When the tetraphenylethylene group is replaced by the triphenylamine group, the two-photon absorption peak is greatly red-shifted, and the two-photon absorption intensity is significantly increased. Since all of these molecules contain tetraphenylethylene or triphenylamine group with propeller structure, they can have both two-photon absorption and aggregation induced emission properties. This study provides theoretical guidelines for synthesizing a new type of active two-photon absorption and aggregation induced emission material.