Naphthyl-Fused Phosphepines: Luminescent Contorted Polycyclic P-Heterocycles

The article presents the synthesis of a new family of naphthyl-fused phosphepines through Ni-mediated C-C coupling. Interestingly, the chloro-phosphine-oxide intermediate shows strong resistance toward oxidation/hydrolysis due to a combination of steric hindrance and pnictogen interactions. However it can undergo substitution reactions under specific conditions. The optical / redox properties and the electronic structure of these new pi-systems were studied experimentally and computationally. Taking advantage of the luminescence of these derivatives, a blue emitting OLED has been prepared highlighting that these novel pi-conjugated P-heterocycles appear as promising building blocks for solid-state lightning applications.