Naphthyl-fused phosphepines: Luminescent contorted polycyclic P-heterocycles

the article presents the synthesis of a new family of naphthyl-fused phosphepines through Ni-mediated CC 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 (UV-vis absorption, emission, cyclic voltammetry) and computationally (TD-DFT calculations, NICS investigation). 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.