title: Key Role of End-Capping Groups in Optoelectronic Properties of Poly-p-phenylene Cation Radicals.
abstract: Poly-p-phenylenes (PPs) are prototype systems for understanding the charge transport in π-conjugated polymers. In a combined computational and experimental study, we demonstrate that the smooth evolution of redox and optoelectronic properties of PP cation radicals toward the polymeric limit can be significantly altered by electron-donatingiso-alkyl andiso-alkoxy end-capping groups. A multiparabolic model (MPM) developed and validated here rationalizes this unexpected effect by interplay of the two modes of hole stabilization: due to the framework of equivalentp-phenylene units and due to the electron-donating end-capping groups. A symmetric, bell-shaped hole in unsubstituted PPs becomes either slightly skewed and shifted toward an end of the molecule iniso-alkyl-capped PPs or highly deformed and concentrated on a terminal unit in PPs with strongly electron-donatingiso-alkoxy capping groups. The MPM shows that the observed linear 1/nevolution of the PP cation radical properties toward the polymer limit originates from the hole stabilization due to the growing chain ofp-phenylene units, while shifting of the hole toward electron-donating end-capping groups leads to early breakdown of these 1/ndependencies. These insights, along with the readily applicable and flexible multistate parabolic model, can guide studies of complex donor-spacer-acceptor systems and doped molecular wires to aid the design of the next generation materials for long-range charge transport and photovoltaic applications.
authors.affiliation: Department of Chemistry, Marquette University , P.O. Box 1881, Milwaukee, Wisconsin 53201-1881, United States.
authors.forename: Marat R
authors.initials: MR
authors.lastname: Talipov
authors.affiliation: Department of Chemistry, Marquette University , P.O. Box 1881, Milwaukee, Wisconsin 53201-1881, United States.
authors.forename: Anitha
authors.initials: A
authors.lastname: Boddeda
authors.affiliation: Department of Chemistry, Marquette University , P.O. Box 1881, Milwaukee, Wisconsin 53201-1881, United States.
authors.forename: Qadir K
authors.initials: QK
authors.lastname: Timerghazin
authors.affiliation: Department of Chemistry, Marquette University , P.O. Box 1881, Milwaukee, Wisconsin 53201-1881, United States.
authors.forename: Rajendra
authors.initials: R
authors.lastname: Rathore