Linear Extension of Anthracene via B←N Lewis Pair Formation: Effects on Optoelectronic Properties and Singlet O<sub>2</sub>Sensitization
Mukundam Vanga, Ashutosh Sahoo, Roger A. Lalancette, Frieder Jäkle
Abstract
Abstract The functionalization of polycyclic aromatic hydrocarbons (PAHs) via B←N Lewis pair formation offers an opportunity to judiciously fine‐tune the structural features and optoelectronic properties, to suit the demands of applications in organic electronic devices, bioimaging, and as sensitizers for singlet oxygen generation. We demonstrate that the N‐directed electrophilic borylation of 2,6‐di(pyrid‐2‐yl)anthracene offers access to linearly extended acene derivatives Py‐BR (R=Et, Ph, C 6 F 5 ). In comparison to indeno‐fused 9,10‐diphenylanthracene, the formal “BN for CC” replacement in Py‐BR selectively lowers the LUMO, resulting in a much reduced HOMO–LUMO gap. An even more extended conjugated system with seven six‐membered rings in a row ( Qu‐BEt ) is obtained by borylation of 2,6‐di(quinolin‐8‐yl)anthracene. Fluorinated Py‐BPf shows particularly advantageous properties, including relatively lower‐lying HOMO and LUMO levels, strong yellow‐green fluorescence, and effective singlet oxygen sensitization, while resisting self‐sensitized conversion to its endoperoxide.