Theoretical investigation on the one- and two-photon absorption properties of a series of porphyrazines with annulated 1,2,5-thiadiazole and 1,4-dimethyloxybenzene moieties

On the basis of equilibrium geometries optimized by B3LYP/6-31G(d) method, the one-photon absorption properties of a series of substituted porphyrazines have been investigated theoretically using time-dependent density functional theory and the semiempirical ZINDO method, respectively. The comparisons with the available experimental data confirmed that the reliability of the ZINDO method in predicting the electronic absorption properties. According to the one-photon absorption properties obtained from the ZINDO method, two-photon absorption properties of molecules have been studied, using ZINDO and sum-over-states methods. The results have showed that the molecule with symmetrically substituted with electron donors exhibits the maximum two-photon absorption cross-section (up to 5276.8 GM) in all the studied molecules. The molecular centrosymmetry has a positive effect on the enhancement of the two-photon absorption cross-section. For the molecules with multi two-photon absorption peaks, the cross-section in the region from 750 to 860 nm is enhanced by one order of magnitude compared with that in the region from 1050 to 1200 nm.