Bipyridinium Bis Hexafluorophosphate Research Articles

Electrochemically responsive nanofibers by stimulation of a dialkyl-bipyridinium molecular switch

The translation of the well-known reversible electrochemical switching of viologen species from solution to the solid state may open enormous possibilities for developing electrically responsive materials. In this work, we present and discuss the electrochemical response of a viologen derivative, 1,1′-dipropyl-4,4′-bipyridinium bis-hexafluorophosphate (Bpy2+), embedded into a polyurethane fibrous matrix. The results showcase the possibility of stimulating electrochemically the active molecule inside the polymer fibers, both in random and aligned configurations, retaining the fibrous morphology and structure while avoiding the use of conductive polymers and ionic liquids, thus opening a new scenario in electrochemically responsive soft actuators.

Quartz Crystal Microbalance and Electrochemical Studies on a Viologen Thiol Incorporated in Phospholipid Self-Assembled Monolayers

Binary self-assembled monolayers (SAMs) were prepared on gold surfaces by use of a viologen, N-methyl-N'-(10-mercaptodecyl)-4,4'-bipyridinium bishexafluorophosphate (V 1 0 SH) and a phospholipid, dipalmitoylphosphatidylthioethanol (DPPTE). Quartz crystal microbalance (QCM) measurements indicated a similar adsorption trend for the V 1 0 SH and DPPTE assembling on the gold surface. Well reversible redox waves of V 1 0 SH and Fe(CN) 6 3-/4- were recorded for the electrodes modified by either pure V 1 0 SH SAM or binary SAMs prepared in mixed solutions of V 1 0 SH and DPPTE with molar ratios below 1:5. Chronocoulomograms of the SAM-modified electrodes indicated that V 1 0 SH acted as an electron-transfer mediator for the Fe(CN) 6 3-/4- ions in the electrolyte solution to gated access to the electrode surface across the DPPTE monolaver.

Does thiol-functionalized viologen monolayer memorize anion present when forming the monolayer?

We investigated the effect of the presence of an additive anion while forming a self-assembled monolayer of a thiol-functionalized redox active species upon the behavior in aqueous solutions. A bromide salt was added in an acetonitrile solution of a thiol-functionalized viologen (viologen-thiol: N-pentyl-N′-(11-mercapto)undecyl-4,4′-bipyridinium bishexafluorophosphate) in which the self-assembled monolayer was formed on a polycrystalline Au electrode. We examined the structure and electrochemical behavior of the resulting monolayer-modified electrode in three different aqueous electrolyte solutions. The viologen-thiol monolayer prepared in the presence of Br− exhibited obviously different behavior in both KBr and KF electrolyte solutions from that prepared in the absence of Br−. On the other hand, the difference was minor in KPF6 solution. The difference of the electrochemical behavior was represented by the coverage of the viologen-thiol and the formal potential of viologen dication/radical cation redox couple. The memory that the viologen-thiol monolayer was formed in the presence of Br− was retained in KF and KBr solutions, though it was erased in the electrolyte solution containing PF6−, which is a softer anion than Br−. However, no definitive difference of the film structure was deduced from the electroreflectance study in regard to the monomer content and the average orientation of the viologen moiety.