Theoretical Study of the Effects of Electron Density Distribution in Frontier Orbitals with Open- Shell Graphene Fragments

Open-shell fragments of graphene have attracted increased attention in recent years because oftheir unique spin carrier property. Through the experimental efforts, these neutral π-radicals could bestabilized by steric protection or delocalized π-conjugated system, such as the phenalenyl-basedmolecules. Here, we use zero sum rule to extend the molecular size and investigate their electronicproperties. The molecules studied in this work can be categorized into two kinds of open-shell structures:the ones with even electron density distribution in the frontier orbitals and the ones with unevendistribution. These molecules afford small reorganization energies in our computational results,especially in the even distribution case (smaller than 19 and 34 meV for hole and electron transfer,respectively). These ultra-low values can be interpreted with the strong nonbonding character in thefrontier orbitals, so that the bond length alteration is small during charge transfer. Considering theoverlap of bilayer open-shell graphene fragments, the even distribution molecules exhibit largerelectronic coupling and binding energy than the uneven. Therefore, we propose that open-shellgraphene fragments with uniform electron density distribution in the frontier orbitals would be bettercharge transfer materials than the ones with uneven electron density distribution. References[1] Y. Morita, S. Suzuki, K. Sato and T. Takui, Nat. Chem., 3 (2011), 197.[2] S. Nishida, K. Kariyazono, A. Yamanaka, K. Fukui, K. Sata, T. Takui, K. Nakasuji, and Y. Morita,Chem. Asian J., 6 (2011), 1188.[3] E. V. Anslyn and D. A. Dougherty, Modern Physical Organic Chemistry (University Science Books,Sausalito, 2006).[4] M. Y. Kuo, H. Y. Chen, and I. Chao, Chem. Eur. J., 13 (2007), 4750.[5] Y. C. Chang and I. Chao, J. Phys. Chem. Lett., 1 (2010), 116.