•We have synthesized four D–π–D dyes with two-photon absorption.•Four dyes contain phenothiazines/carbazoles with styrene/biphenylethyne as bridge.•Photophysical properties of four dyes were investigated.•Donors have larger contribution to σ value than that of conjugated bridge.•Four dyes can be used as organic two-photon photopolymerization initiators.A specific series of dumbbell-shaped bis-carbazoles or bis-phenothiazines dyes (1, 2, 3 and 4) constructed with styrene or biphenylethyne as the π-bridge have been synthesized and characterized. Detailed spectral properties including linear absorption, one and two-photon fluorescence properties were investigated. The results show that extending conjugated chain and introducing donors have substantial effect on their photophysical properties. Among them, two-photon absorption cross sections (σ) of the four dyes in DMF determined by the Z-scan technique are successively increased from 1 to 4 with enhancing electron-donating ability and extending conjugated chain, but electron-donating ability has larger contribution to the σ values than extending conjugated chain based on the comparison of small molecules (D–π–D). Two-photon initiation polymerization (TPIP) microfabrication experiments have been carried out using compound 4 as an initiator under irradiation of 200 fs, 76 MHz femtosecond laser at 760 nm. The results confirm that the four dyes can be effectively used as organic two-photon photopolymerization initiators.Graphical abstractA new series of dumbbell-shaped bis-carbazoles and bis-phenothiazines chromophores (1, 2, 3 and 4) constructed with styrene or biphenylethyne as the π-bridge have been synthesized and characterized. Experimental results revealed that extending conjugated chain and introducing donors have substantial effect on their photophysical properties. Compared with extending conjugated chain, enhancing electron-donating ability play a major role in enlarging two-photon absorption cross-sections (σ). Moreover, those four chromophores can be used as effectively organic two-photon photopolymerization initiators.
