The Impact of Donor-Orientation on the Emission Properties of Chlorinated Trityl Radicals

Chlorinated trityl radicals functionalized with electron-donating groups are promising red-emitting materials for optoelectronic and spintronic applications, overcoming the spin-statistical limit of conventional emitters. Donor functionalization induces charge transfer character, enhancing photoluminescence quantum yield, which depends on the donor strength and its orientation. However, donor functionalized tris(trichlorophenyl)methyl radicals show lower quantum yield than their perchlorinated derivatives, likely due to weaker donor-acceptor electronic coupling and enhanced non-radiative decay. We present a novel trityl derivative with two additional chlorines that restrict the orientation of the donor to a nearly perpendicular arrangement towards the trityl plane, minimizing vibronic coupling and non-radiative losses. Spectroscopic and computational studies reveal that this steric con-straint improves the photoluminescence quantum yield compared to the tris(trichlorophenyl)methyl analogues. These findings highlight the potential of donor-acceptor decoupling to enable efficient, red-shifted emission, offering a design strategy for high-performance radical emitters.