Four new two-photon polymerization initiators with varying donor and conjugated bridge: Synthesis and two-photon activity

A 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.