On the electrochemistry and spectroelectrochemistry of small model star-shaped compounds: 1,3,5-triaryl-1-methoxybenzenes and 2,4,6-triaryl-1,3,5-trimethoxybenzenes.

Model structures of 1,3,5-triarylbenzenes with a substituted benzene core linked to thienyl or 3,4-ethylenedioxythienyl (EDOT) terminal groups are studied by electrochemical and in situ ESR/UV/Vis/NIR spectroelectrochemical techniques. Oxidative polymerization of the monomers results in C-C coupling of the thiophene moieties in the 5-position, forming dimeric structures with bithiophene linkers as the first step. Both the doubly charged protonated dimer and the new dimer formed after proton release are studied in detail for 2,4,6-tris[2-(3,4-ethylenedioxythienyl)]-1-methoxybenzene. Quite high stability of the doubly charged σ dimer formed on oxidation with unusual redox behavior at the electrode is observed. Density functional calculations of the molecular structure as well as spectroscopic and electronic properties of charged states in 1,3,5-triarylbenzene derivatives in the monomeric, dimeric, and oligomeric form are presented. The complex spectroelectrochemical response of a thin solid film formed on the electrode surface upon potentiodynamic polymerization indicates the existence of different charge states of oligomeric structures within the solid matrix.