Electronic and Magnetic Properties of Oligomers and Chains of Poly(benzodifurandione) (PBDF), A Highly Conducting n-Type Polymer

The seminal development of highly electrically conductingpolyacetylenevia oxidative or reductive treatment (doping) hascontinuously inspired the search for other conducting & pi;-conjugatedpolymers. Recently, poly(benzodifurandione), PBDF, was reported tohave unexpected solubility given the absence of side chains and toexhibit an unprecedented, high electrical conductivity upon reduction(n-doping), with protons acting as counterions. Here,we theoretically investigate the electronic and magnetic propertiesof PBDF by taking long oligomers and one-dimensional (1D) periodicchains as model systems. With the oligomer models, we characterizethe formation of polarons and bipolarons in n-doped PBDF. Our resultsindicate that singlet bipolarons tend to be the energetically mostfavorable species when protons bind to two closely located carbonylgroups in nearest-neighbor benzodifurandione moieties. The calculationson the 1D periodic chain models show that the positions of the protonatedcarbonyl groups determine the metallic, semiconducting, or insulatingnature of a PBDF chain. When the protonated carbonyl groups are allsituated on the same side of a PBDF chain, a stable helical chainconfiguration is found that exhibits ferromagnetic behavior. Our findingselucidate the mechanism of polaron and bipolaron formation in longoligomers of n-doped PBDF and highlight the fascinating electronicand magnetic properties of periodic 1D chains. These studies alsoprovide a stepping stone for investigations of PBDF thin films, forwhich two- and three-dimensional structures must be considered.

Automated summary

Theoretical investigations on poly(benzodifurandione) (PBDF) reveal its high electrical conductivity and unexpected solubility upon reduction (n-doping), with protons acting as counterions. The formation of polarons and bipolarons in n-doped PBDF and the electronic and magnetic properties of periodic 1D chains are elucidated.