Impact of non-symmetric 2,9,10-aryl substitution on charge transport and optical properties of anthracene derivatives

• Selective bromination of 2-substituted anthracenes to 10th position.
• 2-phenylanthracenes with different substituents at 9th and 10th positions.
• Blue fluorescence with fluorescence quantum yield up to 0.5.
• Very high hole drift mobility reaching 0.01 cm2/V at 1 MV/cm field.

A new methodology for the synthesis of non-symmetric 2,9,10-arylanthracenes is proposed. The anthracenes were intentionally decorated with non-symmetric aryls to improve charge transport properties. The impact of non-symmetric aryl substituents on optical and electrical properties was thoroughly studied. Non-symmetric 9,10-aryl substituents ensured blue emission in the range of 422–436 nm and fluorescence quantum efficiency of ca. 0.45, while the type of substituents had a minor impact on excited state deactivation due to their twisted configuration. Optical properties of the compounds obtained in dilute solution and in a rigid polymer matrix revealed the dominating non-radiative decay mechanism to be due to the intersystem crossing (ISC), which was mainly governed by 2-phenyl substitution. Favourable alignment of the singlet and triplet energy levels for efficient ISC was confirmed by density functional theory calculations. Some of the non-symmetrically substituted anthracene derivatives showed very high hole drift mobilities reaching 10−2 cm2/Vs in solution-processed neat films.

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