Reviewing extrapolation procedures of the electronic properties on the π-conjugated polymer limit.
In this article, the extrapolation procedures of π-π* electronic transition energy on π-conjugated oligomers are reexamined. Different models, including the simplest coupled oscillator, the free electron, the Hückel approach, the molecular exciton model, and some specific fitting-functions, are compared using the transition energies derived from theoretical calculations on three thiophene-based oligomer series. Specifically, oligomers of up to 30 repeating units have been considered to include the saturation effects as a function of chain length. The coupled oscillator model of W. Kuhn and the fitting-function of Hirayama are the models that present the better suit on the transition energy interpolation as a function of chain length. Using only the first four oligomers of the series (n = 2 up to 8) yields an estimation of the transition energy on the polymer limit with an average error of ∼1.5%. The vertical and adiabatic ionization potential present a better fit with the Hückel model approach. Finally, implications of the environmental polarity on the electronic properties, molecular geometry, charge distribution, and aromaticity are shortly discussed.
Departament d'Enginyeria Química, Escola d'Enginyeria d'Igualada, Universitat Politècnica de Catalunya, Pça Rei 15, Igualada 08700, Spain. joan.torras@upc.edu
Juan
J
Torras
Jordi
J
Casanovas
Carlos
C
Alemán
D004583:Electrons; D015394:Molecular Structure; D011108:Polymers / Q000737:chemistry*; D011789:Quantum Theory
D011108:Polymers