Synthesis and charge transport properties of unsymmetrical meso-substituted tetrabenzoporphyrin derivatives Kazuya Miyazaki 1 , Kyohei Matsuo 2 , Naoki Aratani 1 , Hiroko Yamada 2 1 Nara Institute of Science and Technology, Japan, 2 Institute for Chemical Research, Kyoto University, Japan One of the key issues in the development of organic field-effect transistor (OFET) materials is the improvement of charge mobility. Since charge mobility depends on intermolecular interactions in solid state, it is important to control the crystal structure. The current mainstream OFET materials such as acenes and heteroacenes have one-dimensionally (1D) extended polycyclic aromatic frameworks, and the effect of substitution on the crystal structure has been intensively studied. However, molecular design strategy to control the crystal structure of two- dimensionally (2D) p-extended organic semiconductor has not been intensively explored. Tetrabenzoporphyrin (TBP) is a useful building block as an organic semiconductor due to its chemical stability, large absorption coefficient in visible region, and strong p-stacking interaction. We previously synthesized 5,15-bis(triisopropylsilylethynyl)tetrabenzoporphyrin (TIPS-TBP) and its metal complexes [1,2]. TIPS-TBP shows excellent OFET properties with a maximum hole mobility of 1.1 cm 2 V –1 s –1 , when it takes the 2D brickwork packing structure [3]. However, most of its analogues formed 1D columnar structure, which generally exhibits lower hole mobilities in the thin film FETs. In our previous studies, we succeeded in controlling its polymorphism by optimizing the substituents and deposition condition [4,5], but the crystal structure control of TBP by structural modification remained a challenge. In this study, we synthesized an unsymmetric meso-substituted TBP derivative and its zinc(II) complex to demonstrate the effect of molecular symmetry on the crystal packing. Both compounds showed identical crystal structures and formed 2D herringbone-like packing structures consisting of slipped p-stacking with an antiparallel manner in the crystal. This result is in contrast to the fact that the crystal structure of the symmetric TIPS-TBP is altered by the introduction of central metals [4]. Unsymmetric molecular structure would make 2D p-stacking more stable than 1D columnar structure to counteract steric and electronic imbalance in the crystal. OFETs using unsymmetric TBP derivative and zinc complex achieved the maximum hole mobility of 0.71 and 0.55 cm 2 V –1 s –1 , respectively. These mobilities are superior to those of thin films of TIPS-BP in 1D columnar packing, and comparable to that in 2D brickwork packing. References 1. Takahashi, K.; Kuzuhara, D.; Aratani, N.; Yamada, H. J. Photopolym. Sci. Technol. 2013, 26, 213–216. 2. Takahashi, K.; Yamada, N.; Kumagai, D.; Kuzuhara, D.; Suzuki, M.; Yamaguchi, Y.; Aratani, N.; Nakayama, K.; Yamada, H. J. Porphyrins Phthalocyanines 2015, 19, 465–478. 3. Takahashi, K.; Shan, B.; Xu, X.; Yang, S.; Koganezawa, T.; Kuzuhara, D.; Aratani, N.; Suzuki, M.; Miao, Q.; Yamada, H. ACS Appl. Mater. Interfaces 2017, 9, 8211–8218. 4. Zhu, J.; Hayashi, H.; Chen, M.; Xiao, C.; Matsuo, K.; Aratani, N.; Zhang, L.; Yamada, H. J. Mater. Chem. C 2022, 10, 2527–2531. 5. Jeong, E.; Ito, T.; Takahashi, K.; Koganezawa, T.; Hayashi, H.; Aratani, N.; Suzuki, M.; Yamada, H.; ACS Appl. Mater. Interfaces 2022, 14, 32319–32329.
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