Tuning the antiaromatic character and charge transport of pentalene-based antiaromatic compounds by substitution

Understanding the structure-property relationships in antiaromatic molecules is crucial for controlling their electronic properties and designing new organic optoelectronic materials. Here we report the design, synthesis, and characterization of three new antiaromatic molecules (Pn, n = 1-4) based on the pentalene (P) antiaromatic core, to investigate how electron-donating and electron-accepting substituents affect P1-P4 properties. As expected, the optical, HOMO and LUMO energy levels and electronic structure are greatly modulated by core substitution. Compared to the unsubstituted compound (P1), P3 and P4 containing strong electron-withdrawing units reduced antiaromaticity as assessed by nucleus-independent chemical shift (NICS) calculations compared with P2, which is functionalized with strong electron-donating units, showing that substitution strongly tunes local antiaromaticity. Organic field-effect transistors (OFETs) fabricated using these materials indicate that P2 has an average hole mobility of ∼10-4 cm2 V-1 s-1 while P3 has an average electron mobility of up to 0.03 cm2 V-1 s-1, versus FET-inactive P1. Therefore, introduction of strong π-extended electron-withdrawing or electron-donating substituents onto an antiaromatic core is an effective strategy to switch-on charge transport capacity.