Systematic Study of the Influence of Several Parameters on Physicochemical Properties of Oligoanilines and their Derivatives

Abstract

In this work we study the influence of asymmetry, chain length, oxidation state, counterions and substituents groups over the physicochemical properties of oligoanilines. We present some semiempirical quantum chemistry calculations of optimized structures, charge distributions, energy gaps and enthalpies of formation (ΔHf) for aniline oligomers in different oxidation states using the AMI method. Also, substituted structures are caicuiated. The substituents studied are methoxy, methyl and cyano groups located at positions 2 or 3 in the benzenoid ring. Methoxy substituted tetraanilines show hydrogen bridge formation; therefore, these are the most stable structures. The cyano group (σ-π acceptor) induces a lowering of charge on the terminal amine group in all oxidation states. Our calculations show that a linear relationship exists between charge on terminal amine group and the IP. having different slope values depending on the substituents position. Theoretical energy gaps and experimental ones (from references) display a quite linear relationship. Tetraanilines substituted with cyano groups show the lowest energy gap and is the most interesting material that we have studied. Moreover, charged structures have been analyzed. Calculations on radical cation and dication structures are introduced. The influence of the counterions on the electronic properties of charged structures is presented.