Synthesis and Characterization of Novel 1,4-Bis(carbazolyl)benzene Derivatives with Blue-Violet Two-Photon-Excited Fluorescence

Abstract

Novel fluorescent two-photon absorption molecules containing bis(carbazolyl)benzene as the central unit and phenylethynyl moieties as peripheral groups (Cz-Ps) are synthesized and characterized. In these molecules, two carbazolyl moieties are linked with benzene at the 9-position and synthesized by a concise process involving nucleophilic substitution between the cyclopentadienyliron complexes of dichloroarenes and phenylethynyl carbazole, followed by photolysis. The optimal structures of Cz-Ps reveal that two carbazolyl rings linked by a benzene ring are not planar. This feature prevents the electron conjugation of the molecule from extending throughout the whole molecule and allows Cz-Ps to realize blue-violet emissions and high fluorescence quantum yield. With increasing number of conjugated phenylacetylene structures in Cz-Ps, the maximal absorption and emission peaks were red-shifted. The quadrupolar compound DMoCz-P shows strong one-photon and twophoton activities. The resulting molecules are also thermally stable with high glass transition temperatures due to the rigid bicarbazole central unit. This work has demonstrated that using bis(carbazolyl)benzene as central building block could enhance two-photon absorption (TPA) performance and also provides a possible general synthetic strategy for a series of bis(carbazolyl)benzene derivatives, which would advance the understanding of the rational design of new organic optical materials.

Recent Advances and Challenges in Long Wavelength Sensitive Cationic Photoinitiating Systems

“…Thanks to their photoconductive properties and facile oxidation, carbazoles are widely used in the design of organic materials and PIs [118]. In a recent study by Zhu et al [119], N-methylpyrrole was also found to be a very effective molecule for the design of functional PIs.…”

Exploring the 3-(phenylethynyl)-9H-carbazole unit in the search of deep-blue emitting fluorophores

“…Synthetically, the structures of the herein presented carbazole derivatives consist in the attachment of additional aromatic moieties to the carbazole core through a triple bond spacer. This spacer provides rigidity and planarity, favoring conjugation and π-electron delocalization, which is of interest in the design of new fluorophores [25][26][27]. In fact, the 3-(phenylethynyl)-9H-carbazole unit as a synthetic building block has already proved to efficiently provide blue emission in OLEDs, especially within the deep-blue region [28,29].…”