Dr. Veronika Laurinavichyute
Department of Electrochemistry, M.V. Lomonosov Moscow State University, Russian.

Speech title: Ionic Interactions in the Polyviologens – K4Fe(CN)6 systems

Abstract: Ionic interactions in the polyviologens – K4Fe(CN)6 systems V.K. Laurinavichyute1*, L.V. Pugolovkin1, V.Yu. Kotov2, M.N. Zhidkova2 1 Department of Chemistry, Moscow State University, Moscow 119991, Russia 2N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation Polyviologens are the promising materials for a number of applications, for example they can be used as charge-storage materials in dye-sensitized solar cells or as a principle component of electrochromic layer in smart windows. All these applications are mainly associated with the highly reversible redox activity of polyviologens which is accompanied by the anionic transport across the film in course of charge compensation process. The special role of different anions in electropolymerization of polyviologens or redox properties of the resulted films is widely accepted, however mainly the size effect of counter anions is usually emphasized. In the current report we focus on the different mechanisms of ionic interactions inside the polyviologen films and their possible impact on electropolymerization process and the resulting film properties. Various oligoviologen derivatives were synthesized by Menshutkin reaction of 4,4′-bipyridine (BPy) with α,ω-dibromoalkanes (α,ω–CnH2nBr2, n = 2-6). Polyviologens of the same composition were synthesized by electrochemical polymerization of bis(4-cyano-1-pyridino)alkanes derivatives. The current efficiency of electropolymerization was found to increase with varying the counter anion in the row: [Fe(CN)6]3-< Br-< [Co(CN)6]3 ~[Fe(CN)6]4-. The obtained oligo- and polyviologens and their interaction with different anions (F-, Cl-, Br-, I-, [Fe(CN)6]4?) were characterized by 1H NMR, cyclic voltammetry, electronic absorption spectroscopy and EDX analysis. Two principally different types of interaction between oligo/polyviologens and hexacyanoferrate ions were established. The first one is a fast reversible outer-sphere charge transfer complex formation with or without inclusion of cations. The second mechanism includes slow irreversible formation of the inner-sphere complex [Fe(CN)5L]q± with the participation of oligomer terminal groups. The possible effects of charge transfer between [Fe(CN)6]4? anions and viologen moieties will be also discussed.