Redox states of well-defined pi-conjugated oligothiophenes functionalized with poly(benzyl ether) dendrons

The redox states of a series of well-defined hybrid dendrimers based on oli gothiophene cores and poly(benzyl ether) dendrons have been studied using c yclic voltammetry and variable-temperature UV/visible/ near-IR spectroscopy . The oxidation potentials and the electronic transitions of the neutral, s ingly oxidized, and doubly oxidized states of these novel hybrid materials have been determined as a function of oligothiophene conjugation length var ying between 4 and 17 repeat units. The attachment of poly(benzyl ether) de ndritic wedges at the termini of these lengthy oligothiophenes considerably enhances their solubility, thus enabling the first detailed investigation of the electronic structure of oligothiophenes having Il and 17 repeat unit s with minimal beta-substitution. In the case of the undecamer and heptadec amer, we find that the dicationic state consists of two individual polarons , rather than a single bipolaron. The effect of the dendritic poly(benzyl e ther) solubilizers on the properties of the redox states varies with the ol igothiophene length and dendron size. More specifically, we observe a kinet ic limit to the electrochemical oxidation of the oligothiophene core when t he dendron is large compared to the electrophore. Finally, we have observed the first example of self-complexation of cation radicals via pi-dimerizat ion leading to the formation of dendritic supramolecular assemblies.