Recently, there has been increasing interest in a class of polycyclic aromatic hydrocarbons (PAHs) with peri-extension of acenes. These peri-fused systems, referred to as peri-acenes and acenoacenes, are considered to be nanographenes.[1–3] Thus, the compounds based on tetracene and larger acenes show singlet biradical nature at the zigzag edge, offering unique and interesting properties.

However, the synthesis schemes for these compounds are generally complicated, which hinder the extensive development of these derivatives and application to organic optoelectronics such as organic field-effect transistors (OFETs) and organic light-emitting diodes (OLEDs). A pentacene derivative with two triisopropylsilylethynyl groups at the central ring (TIPS-PEN) was developed in 2001. It shows good solubility, stability, and semiconducting property, resulting in being one of the most studied organic semiconductors. In contrast, the peri-extended compound of TIPS-PEN has not been developed because of the difficulty in synthesis using the same method as TIPS-PEN.[4] Here, we found the synthetic conditions to avoid the competition between 1,2- and 1,4-addition of lithium acetylide on large aromatic dione and succeeded in synthesizing TIPS-ethynyl-substituted peri-pentacenopentacene (TIPS-PPP).[5]

The stability of TIPS-PPP was 16 times superior to that of TIPS-PEN, which is attributed to higher aromaticity as shown in an electronic structure of two-fused anthracene. TIPS-PPP shows the crystal packing of the 2D-brickwall motif like TIPS-PEN. The high mobility of up to 1 cm² V⁻¹ s⁻¹ was obtained in OFET fabricated by wet process owing to large transfer integrals and low reorganization energies. In addition, TIPS-PPP showed high quantum yield in near-infrared (NIR) region. Thus, it was used as an emitter for NIR-OLED devices, resulting in high external quantum efficiency at 800 nm. These results suggest that acene-like materials are very promising for developing NIR emitters.

References

[1] M. Mamada, R. Nakamura, C. Adachi, Chem. Sci. 2021, 12, 552.

DOI: 10.1039/D0SC04699J

[2] T. Jousselin-Oba, M. Mamada, J. Marrot, A. Maignan, C. Adachi, A. Yassar, M. Frigoli, J. Am. Chem. Soc. 2019, 141, 9373.

DOI: 10.1021/jacs.9b03488

[3] Y. Gu, Y. G. Tullimilli, J. Feng, H. Phan, W. Zeng, J. Wu, Chem. Commun. 2019, 55, 5567.

DOI: 10.1039/c9cc01986c

[4] X. Zhang, J. Li, H. Qu, C. Chi, J. Wu, Org. Lett. 2010, 12, 3946.

DOI: 10.1021/ol101720e

[5] T. Jousselin-Oba, M. Mamada, K. Wright, J. Marrot, C. Adachi, A. Yassar, M. Frigoli, Angew. Chem. Int. Ed. 2021,

DOI: 10.1002/anie.202112794.