Theoretical investigations on one and two-photon absorption properties of 1,4-di(4'-N,N-diphenylaminostyryl)benzene derivatives

With the development of two-photon microscopy, getting excellent two-photon fluorescence dyes become a hot topic. In this work, the equilibrium geometries, electronic structures, one- and two-photon absorption properties and the fluorescent emission properties for a series of D-π-A-π-D type 1,4-di(4'-N,N-diphenylaminostyryl)benzene (DPA-DSB) derivatives were investigated by the density functional theory (DFT). The results show that the one photon absorption wavelengths of this series of one-dimensional linear conjugated molecules are in the range 370~540 nm, fluorescence emission wavelengths are in the range 435~700 nm, provided the absorption of the UV to green light and the emission of the all visible range. The Stokes shifts are in the 47~270 nm range. Thus, these molecules provide broad color fluorophore options molecules for biological fluorescence imaging and fluorescence microscopy. The response function approach has been used to calculate the two-photon properties. Analysis of two-photon properties of these molecules suggests that these molecules two-photon absorption wavelengths are at 650~880 nm. The molecules 2, 4, 5, 6, 8 and 12, 14 have two-photon absorption in the infrared light range, which means these molecules can be used as alternative molecules to design the infrared medical material. These molecules have the fluorescence signal in the visible range and excellent two-photon characteristics; can be used as two-photon fluorescent probes biomarkers and alternative materials. Analyzing its structure and optical properties indicate that the modification or replacement of the electron-withdrawing group in the center of the molecule can effectively shift its electronic spectrum, the addition of N atom or S atom can significantly improve the two-photon absorption cross-section. For the acetylenyl moiety as π bridge, if the molecular plane did not change compared with ethylene bridge, it makes the two-photon absorption cross-section decreases; if acetylene bridge improved the planarity of molecule, it causes two-photon absorption cross-section increases. This study aims to understand the relationship between molecular structure and two-photon properties and offer some important information for the design and synthesis of novel materials.