CD-Spektroelektrochemie, eine Methode zur Charakterisierung chiraler Elektronentransferreagentien und chiraler Reaktionszwischenstufen

Assembly of an Axially Chiral Dynamic Redox System with a Perfluorobiphenyl Skeleton into Dumbbell- or Tripod-type Electron Donors

The incorporation of F atoms endows a diethenylbiphenyl-based electron donor with configurational stability and SN Ar reactivity. The former enables the dynamic redox pair of (Rax)-1/(Rax ,R,R)-1(2+) to exhibit drastic UV/Vis and CD spectral changes upon electrolysis, whereas the latter makes it possible for (Rax)-1 to serve as a useful chiral synthon for the production of larger assemblies [(Rax ,Rax)-2 d,p,m and (Rax ,Rax ,Rax)-3] containing two or three dyrex units. These dyads and triad also exhibit a clean electrochiroptical response with isosbestic points owing to one-wave multi-electron transfer.

Multi-input–Multi-output Molecular Response System Based on Dynamic Redox Behavior of Hexaphenylethane-type Electron Donors with the Tetrahydrophenanthrazepine Skeleton: Strong Chiroptical Signals through the Transmission of Point Chirality to Helicity

The title heterocyclic donors undergo reversible C-C bond formation/cleavage upon electron transfer (dynamic redox behavior). The helical sense in both neutral and cationic states is interconvertible by facile ring flipping. The pi-type asymmetric center on the azepine nitrogen atom induces a significant degree of diasteromeric preference, thus endowing strong CD activity based on exciton coupling. Chiroptical properties could be modified not only by redox reactions but also by heat and protonation. The present redox pairs can serve as unprecedented three-way-input (e, H+, delta) and two-way-output (UV/Vis, CD) response systems.

Chemistry of porphyrin-appended cellulose strands with a helical structure: spectroscopy, electrochemistry, and in situ circular dichroism spectroelectrochemistry

Around 100 porphyrin units have been selectively linked at C(6)-O to a cellulose (Avicel). The properties of the metal-free and zincated porphyrin-celluloses 2 and Zn-2 have been determined by optical and electrochemical methods. Circular dichroism indicates a helical arrangement of the porphyrin units and reveals intra-chain coupling reminiscent, in the broadest sense, of strands of nucleic acids. Cyclic voltammetry and spectroelectrochemistry have been used to characterize the radical ions and dianions. The electrochromism of the oxidation of cellulose 2 to porphyrin radical cations of 2 has been employed for both molecular switching and the transduction of an electrochemical input into chiroptical signal expression.