Diketopyrrolopyrrole-based Conjugated Moleculars: Design,synthesis And Optical Property Study

As a kind of organic dyes,diketopyrrolopyrrole(DPP)have their unique advantages.This is due to the DPP is a brilliant light,heat stability,chemical resistance,good thermal stability,easy synthesis of high-performance dyes.DPP has attracted considerable research interest in the past few years.DPP derivatives are widely used in organic solar cells(OSCs),organic field effect transistors(OFETs),two-photon absorption materials,fluorescent probes and other fields.In this paper,six DPP based compounds M1 to M6 were designed.The purpose of this study was to make a breakthrough and progress in the effect of aggregation and large two-photon absorption cross section of DPP derivatives.Firstly,the target molecule M1,M2,M3 was synthesized by introducing triarylamine groups with good electron donating and transporting capability,and tetraphenylethene groups with a strongly twisted molecular structure and phenomenon of aggregation-induced emission.Through the characterization of the three compounds showed that three compounds in organic solvents such as tetrahydrofuran,toluene,DMF have a good solubility,which also provides a good foundation for our further access groups.M1,M2,M3 have high fluorescence quantum efficiency in organic solvents,such as the quantum efficiency of fluorescence in tetrahydrofuran solution is 0.94,0.93,0.91.In addition,M3 of accessing to tetraphenylethene groups in water content being added to the DMF solvent showed good aggregation-induced emission characteristics,while M1 and M2 have no aggregation induced emission characteristics,it also shows that with AIE effect through the access group can make the plane of reduced molecules,the intermolecular interactions weakened.Aggregation at the nanoscale,non radiation attenuation,the fluorescence enhancement.tetraphenylethene access molecular plane decreased at 820 nm wavelength excitation two-photon absorption cross section of compound M3 is smaller than that of M1 and M2,but after the introduction of tetraphenylethene,increasing the molecular conjugated system,intramolecular charge transfer enhancement and fluorescence emission at low Stokes shift,band region(880 nm),there are two photon is very wide the range of absorption is better than that of compound M1 and M2.Then,M4,M5,M6 compound was synthesized with DPP as the core.We chose the diphenylamine with higher electron donating ability than that of the triarylamine groups,and finally introduced the group with the effect of AIE.We conclude that characterized by distortions due to triarylamine groups than diphenylamine,so although finally introduced tetraphenylethene groups,but M6 compounds did not exhibit a good aggregation-induced emission effect like M3 compounds.This is due to the fact that the diphenylamine makes the M6 molecule planarity better than the M3 compound.Compared with the compound M4,M5,the access of tetraphenylethene groups slows down the quenching effect of compound M6,which makes the molecule change from ACQ to AIE effect.At the 880 nm wavelength,the two-photon absorption cross section of the compound M6 was as high as 618 GM,while the M3 compound excited at this wavelength was only about 237 GM.