Near-Infrared Absorptive and Emissive Poly(p-phenylene vinylene) Derivative Containing Azobenzene–Boron Complexes

Abstract

Poly(p-phenylene vinylene) (PPV) is known to be a typical π-conjugated polymer and used as a commodity platform for constructing optoelectronic organic devices because of superior optical and material properties. PPV derivatives generally show a large degree of light absorption and intense emission in the visible region; meanwhile, very few examples have been reported to offer near-infrared (NIR) absorptive and emissive PPV derivatives. In this study, we designed and synthesized a novel PPV derivative, named BAz-PPV, containing boron-fused N═N double bond units in the main chain. BAz-PPV showed intense NIR absorption and emission (λₐbₛ = 702 nm, λPL = 760 nm, and ΦPL = 2.0% in diluted toluene). This polymer had a narrow energy band gap because of not only extension of main chain π-conjugation over 50 monomer units but also stabilization of the energy level of the lowest unoccupied molecular orbital. Moreover, the polymer shows high stability toward photodegradation and sufficient carrier-transport ability for the applications in organic semiconducting devices. Advantages of the introduction of the N═N double bond to main-chain conjugation followed by boron coordination for the development of NIR materials are demonstrated in this manuscript.