Calculation on the one- and two-photon absorptions properties for two series of dimethylfluorene core derivatives

Two series of dimethylfluorene core derivatives, which have different conjugation length or different peripheral substituted groups, are theoretically investigated in the paper. Using the density functional theory B3LYP with 6-31G basis set, we have obtained the equilibrium geometries and electronic structures for all the studied molecules. On the basis of the geometrical and electronic structures, the one- and two-photon absorptions properties are studied theoretically with ZINDO-SOS method in detail. The computational results are in good agreement with the available experimental values. According to our calculations, from the series I molecule to the series II counterparts, the maximum one-photon absorption (OPA) intensities and the maximum two-photon absorption (TPA) cross sections values δmax are obviously increased as the conjugation length increases. And for both series the maximum OPA wavelength λmax(1) and δmax values are increased with the stronger electron-donating or electron-accepting capability. This demonstrates that the conjugation length and the different substituent groups play important roles in the OPA and the TPA cross section.