Quinoidal units have received increasing interests for use in the design and synthesis of functional organic optoelectronic materials. A key to advance this field is the development of stable and easily accessible quinoidal units. para-azaquinodimethane (AQM) has recently been introduced as a stable, compact and readily available quinoid unit that incorporates nitrogen atoms in the central ring and substituents on the periphery. While AQM has shown impressive ability to tune bond length alternations within conjugated systems, based on which a wide variety of high carrier mobility, low band gap conjugated polymers have be obtained, it behaves as an electronically neutral species that is distinct from classical electron acceptors and electron donors. In this talk, I will present our methods of transforming such “electron neutral” quinoid into both strongly electron-deficient and electron-rich units (Figure 1). Such transformation is based on a facile SNAr type substitution reaction which introduces ionic pyridinium groups. The chemistry allows the “umpolung” of the electron density of the AQM to different extremes, enabling the design and synthesis of ultralow band gap polymers (lowest band gap is ~0.7 eV) that have shown excellent photothermal properties.

Electron affinity umpolung of a stable quinoidal synthon for low band gap conjugated polymers

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ACS Fall 2022

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