Stabilizing\nDiketopyrrolopyrrole Radical Cations Through\nCarbazoles: Substitution Pattern vs Spin Delocalization

The synthesis of organic radicals continues to garner\nsignificant\ninterest due to their fascinating optical, electronic, and magnetic\nproperties. Moreover, the growing demand for chemically stable organic\nradicals is driven by the rapid expansion of the market for electronic\ndevices utilizing organic semiconductors. In this context, the development\nof multifaceted approaches for the design of stable organic radicals\nis of great importance. In this work, we introduce a strategy for\ngenerating stable radical cations of diketopyrrolopyrroles (DPP) by\nmodulating the substitution pattern of the electron-donating carbazole\nsubstituent. Using electronic, spin resonance, and vibrational spectroscopies,\nsupported by density functional theory, we carefully investigated\nthe electronic structures and chemical stability of the DPP radical\ncations. Our findings demonstrate that the position of electron-rich\nheteroatoms and the presence of Clar’s aromatic sextets in\ndonor moieties play a pivotal role in enhancing the chemical stability\nof DPP radical cations.