Nonlinear optical properties and ultrafast responses of Diketo-Pyrrolo-Pyrrole-based conjugated bridge derivatives: A comparative investigation on molecular conjugated bridges selection

Abstract

Two π -conjugated bridge derivatives based on Diketo-Pyrrolo-Pyrrole were selected to investigate the relation between the structure and nonlinear optical response. These two DPP-based conjugated derivatives exhibit intense two-photon fluorescence emission. At a special wavelength of 800 nm, which is the most commonly used wavelength in applications of two-photon absorption/fluorescence materials, the two-photon absorption cross-section of DPP-J0 and DPP-J1 in THF solutions, were determined to be 6 GM and 8 GM, respectively. Degenerated pump-probe technique at wavelength of 800 nm and 400 nm, were performed to investigate the ultrafast relaxation processes of these DPP-based conjugated cores. The intramolecular charge transfer state was determined to be formed in time domain approximately sub-ps, while the evolution lifetimes of the intramolecular charge transfer state are longer than one hundred picoseconds. Our results indicate that DPP-based groups are good candidates of π -conjugated bridges for selecting π -conjugated bridge when design/optimize new two-photon absorption molecules. Besides, alkyl chains also play important effect on the two-photon absorption response.