The Research Dependent On Photophysical Properties Of π Conjugated System Linear Conjugated Oligomers

The optical properties of three linear conjugated oligomers (Fluorene unit and the phenothiazine unit combination (F-P); with thephenothiazine unit as the core, the fluorene unit are respectively arrangedonboth sides of the symmetrical (F-P-F); with the phenothiazine unit as the core,the formation of F-P-F after the phenothiazine unit points set outside offluorene unit (P-F-P-F-P)), where phenothiazine andfluorene groups arrange alternately, they are investigated in detail.With the enhancement of the π-conjugated system, their maximum of absorption and emission band both gradually red shifts. Nonlinear optical measurement shows that their two-photon fluorescence yield and the corresponding absorption cross-section gradually increase. Their fluorescence dynamic traces are detected by time correlated single photon counting technique and simultaneously analyzed with continuous rate distribution model, which exhibits that the decay rate of oligomersgradually accelerate and the distribution width of decay rates become more and more narrow with the introduction of π-conjugated units.The quantum chemical calculation is used to analyze their molecular structures and the electronic transition behaviors, showing that the improvement of two photon properties should be also assigned to the enhancement of π-conjugated system. All the results could be beneficial for us to further investigate the photophysical properties of linear conjugated oligomers.