Ion Transfer Voltammetry at Thin Films Based on Functionalized Cationic [6]Helicenes

Abstract

We describe a new family of molecular ion‐to‐electron redox probes based on cationic diaza, azaoxa, and dioxa [6]helicenes and their derivatives. Their unique structure combines, in a single framework, two privileged families of molecules – helicenes and triaryl methyl carbenium moieties. These cationic [6]helicenes exhibit reversible and reproducible oxidation/reduction behavior and facilitate the ion transfer into thin layer sensing films composed of bis(2‐ethylhexyl)sebacate (DOS), polyurethane (PU), sodium tetrakis 3.5‐bis(trifluoromethyl)phenyl borate, sodium ionophore X and diaza+(C8)2Br2 for cation transfer. Cyclic voltammetry is used to interrogate the thin films. The cationic response can be tuned by adjusting the membrane loading. Addition of lipophilic cation exchanger into the membrane film results in transfer waves of Gaussian shape for cations. A peak separation of 60 mV and peak width of 110 mV are near the theoretical values for a surface confined process. While Nernstian shifts of the peak potentials with analyte concentration is obtained for membranes based on cationic [6]helicenes and doped with sodium‐selective ionophore X, this ionophore was found to promote a gradual loss of redox active species from the ionophore‐based membranes into the sample solution.

Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

“…Other applications in electrochemiluminescence or ion transfer voltammetry were also reported for some [4]-and [6]helicene cationic dyes but focused only on racemic compounds. 282,283,284 In collaboration with Prof. Naaman, Lacour investigated aza [4]helicenium derivative [260][BF 4 ] as potential organic spin filter owing to the Chirality Induced Spin Selectivity (CISS) effect. 285,286 Using magnetic conductive probe atomic force microscopy (mCP-AFM) and magnetoresistance measurements set-ups, the authors showed that spin specific electron conduction is measured on chiral helicenium films with an opposite preferred spin for (P) and (M) enantiomers (Figure 38).…”

Potentiometric Sensing

“…They can be dissolved in the membrane phase and mediate the iontransfer across the interface upon their reduction or oxidation. [75][76][77] Jansod et al…”

“…The ratio between the concentrations of added cation-exchanger and redox probe was found to determine the voltammetric anion or cation response of this system. Cationic diaza, azaoxa, and dioxa [6]helicenes and their derivatives were introduced as another family of molecular redox probes for voltammetric cation 76 and anion 77 is necessary. 77 Unfortunately, it was found that the ionophore based cation- The potentiometric response of nanopores can be understood using the concept of permselectivity in some analogy to conventional polymer membrane ISEs.…”

“…Ion transfer at the membrane-solution interface resulting from the oxidation/reduction of a redox probe in the transducing layer as an analytical tool for ion sensing [68][69][70][71][72][73][74][75][76][77]. On the right, two response regimes are identified depending on the analyte concentration range.…”

Voltammetric Properties of All‐solid State Ion‐selective Electrodes with Multiwalled Carbon Nanotubes‐poly(3‐octylthiophene‐2,5‐diyl) Nanocomposite Transducer

“…Another trend in the development of ion‐selective electrodes, also those with a solid contact, is application of dynamic electrochemical methods to interrogate the sensors . Recently, the most popular electrochemical method in this aspect has been voltammetry with thin ion‐selective membranes coated on electrode supports, containing conducting polymer layers or immobilized redox reagents as a transducer . Voltammetric methods are usually used either in a direct mode (recording a voltammetric curve for electrode immersed in the analyte solution, with peak current position determined by the analyte concentration) or in stripping mode, as shown mainly by Amemiya et al.…”