title: Relation between Nonlinear Optical Properties of Push-Pull Molecules and Metric of Charge Transfer Excitations.
abstract: We establish the relationships between the metric of charge transfer excitation (Δr) for the bright ππ* state and the two-photon absorption probability as well as the first hyperpolarizability for two families of push-pull π-conjugated systems. As previously demonstrated by Guido et al. (J. Chem. Theory Comput. 2013, 9, 3118-3126), Δr is a measure for the average hole-electron distance upon excitation and can be used to discriminate between short- and long-range electronic excitations. We indicate two new benefits from using this metric for the analyses of nonlinear optical properties of push-pull systems. First, the two-photon absorption probability and the first hyperpolarizability are found to be interrelated through Δr; if β ∼ (Δr)(k), then roughly, δ(TPA) ∼ (Δr)(k+1). Second, a simple power relation between Δr and the molecular hyperpolarizabilities of push-pull systems offers the possibility of estimating properties for longer molecular chains without performing calculations of high-order response functions explicitly. We further demonstrate how to link the hyperpolarizabilities with the chain length of the push-pull π-conjugated systems through the metric of charge transfer.
authors.affiliation: Department of Physics, Chemistry and Pharmacy, University of Southern Denmark , Campusvej 55, DK-5230 Odense M, Denmark.
authors.forename: Nanna Holmgaard
authors.initials: NH
authors.lastname: List
authors.affiliation: Department of Physical and Quantum Chemistry, Faculty of Chemistry, Wrocław University of Technology , Wyb. Wyspiańskiego 27, PL-50370 Wrocław, Poland.|Department of Chemistry, Faculty of Natural Sciences, Matej Bel University , Tajovského 40, SK-97400 Banská Bystrica, Slovak Republic.
authors.forename: Robert
authors.initials: R
authors.lastname: Zaleśny
authors.affiliation: Division of Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology , SE-10691 Stockholm, Sweden.
authors.forename: N Arul
authors.initials: NA
authors.lastname: Murugan
authors.affiliation: Department of Physics, Chemistry and Pharmacy, University of Southern Denmark , Campusvej 55, DK-5230 Odense M, Denmark.
authors.forename: Jacob
authors.initials: J
authors.lastname: Kongsted
authors.affiliation: Department of Physical and Quantum Chemistry, Faculty of Chemistry, Wrocław University of Technology , Wyb. Wyspiańskiego 27, PL-50370 Wrocław, Poland.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Bartkowiak
authors.affiliation: Division of Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology , SE-10691 Stockholm, Sweden.
authors.forename: Hans
authors.initials: H
authors.lastname: Ågren
mesh_terms: D015394:Molecular Structure; D055620:Optical Phenomena; D017785:Photons; D011108:Polymers / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D011108:Polymers; C041325:polyphenylene sulfide