Toward the rational design of functionalized pentacenes: reduction of the impact of functionalization on the reorganization energy.

For the widely studied high-carrier-mobility species, pentacene, it is found that perfluorination turned it into an n-type organic field-effect transistor (OFET), but doubled the internal reorganization energy (lambda) of the electron/hole hopping. Here, Cl- and N-functionalized pentacenes are designed to test two strategies that may reduce the impact of functionalization on lambda. Calculation results show that the strategies are feasible. Moreover, combined with crystal-structure data of Cl- and N-functionalized aromatic compounds, it is concluded that compared to fluorination, the presence of Cl and N atoms in pentacene not only reduces the influence of functionalization on lambda and affords a larger window for tuning HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energies, but also provides the opportunity to promote pi-stacked structures through ClCl and C--HN interactions.