A new series of quadrupolar type two-photon absorption chromophores bearing 11, 12-dibutoxydibenzo[a,c]-phenazine bridged amines; their applications in two-photon fluorescence imaging and two-photon photodynamic therapy

A new series of quadrupolar type two-photon absorption (2PA) chromophores 3-9 bearing a core arylamine-[a,c]phenazine-arylamine motif are synthesized in high yields. Palladium-catalyzed Stille coupling and CN coupling reactions are utilized to prepare target chromophores. Detailed characterization and systematic studies of these molecules, including absorption and fluorescence emission, are conducted. These compounds are found to exhibit very large 2PA cross section values, for example, ∼7000 GM at 800 nm for 8 in toluene. Two-photon-induced fluorescence imaging is successfully demonstrated in vitro using compound-8-encapsulated silica nanoparticles with excellent bio-compatibility. In combination with the capability of both one- and two-photon singlet-oxygen sensitizations, this nanocomposite demonstrates its promising potential in dual functionality toward two-photon fluorescence imaging and two-photon photodynamic therapy.