Physicochemical properties of cationic dioxa 1, azaoxa 2 and diaza 3 [6]helicenes demonstrate a much higher chemical stability of diaza adduct 3 (pKR+ 20.4, E1false/2red −0.72 V) compared to azaoxa 2 (pKR+ 15.2, E1false/2red −0.45 V) and dioxa 1 (pKR+ 8.8, E1false/2red −0.12 V) analogues. The fluorescence of these cationic chromophores was established and ranges from the orange to the far-red regions. From 1 to 3, a bathochromic shift of the lowest energy transitions (up to 614 nm in acetonitrile) and an enhancement of the fluorescence quantum yields and lifetimes (up to 31% and 9.8 ns at 658 nm) are observed. The triplet quantum yields and the circularly polarized luminescence are also reported. Finally, fine tuning of the optical properties of the diaza [6]helicene core was achieved through selective and orthogonal post-functionalization reactions (12 examples, compounds 4-15). The electronic absorption is modulated from the orange to far-red spectral range (560-731 nm) while fluorescence is observed from 591 to 755 nm with enhanced quantum efficiency up to 70% (619 nm). The influence of the peripheral auxochrome substituents is rationalized by first-principles calculations.

Cationic hetero[6]helicenes 1+, 2+ and 3+ have been recently disclosed. Herein we report on their enantiomeric separation using high-performance liquid chromatography. Separation of the antipodes can be achieved in preparative scale on neutral adducts with Chiralcel OD-I or Chiralpak ID CSP. Selectivity factors of 1.90, 1.67, and 1.96 were obtained for 1-H, 2-H, and 3-H, respectively. Separation can also be performed on the carbenium ions on regular Chiralpak IA CSP using water-containing eluents, thus allowing for enantiomeric purity determinations in aqueous environments. Resolution of neutral and cationic helicenes is also achieved on more recently developed LARIHC columns. The versatility of the cyclofructan phases allows for baseline separations for both cases and their loading capabilities are demonstrated. Finally, the configurational stability of 1+, 2+, and 3+ was measured. For each replacement of an oxygen atom by an amino group, the racemization barrier increases significantly (ΔG‡ = 29.8, 36.3 and >37 kcal mol(-1) for 1+, 2+, and 3+ respectively).

In one pot, tertiary alkyl amines are oxidized to enamines by cationic dioxa[6]helicene, which further reacts as electrophile and oxidant to form mono or bis donor-p-acceptor coupling products. This original and convergent synthetic approach provides a strong extension of conjugation yielding chromophores that absorb intensively in far-red or NIR domains (l max up to 791 nm) and fluoresce in the NIR as well (l max up to 887 nm). Intense ECD properties around 790 nm with a j De j value up to 60 M À1 cm À1 are observed.

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.

Cationic helicenes are ortho-fused polyaromatics which exhibit well-defined and stable helical conformations with original absorption and emission properties in the red to near-infrared spectral ranges. Herein, a selection of cationic [4] and [6]helicenes are studied for their electrochemical, fluorescence, and electrochemiluminescence (ECL) properties in acetonitrile solutions. Their photophysical and redox responses are drastically tuned by the introduction of auxochrome substituents at their periphery or the interconversion of oxygen and nitrogen atoms within the helical core. All diaza helicenes exhibit a reversible reduction process, whereas in the presence of oxygen instead of nitrogen atoms in the helical core, irreversible oxidations and a decrease of ECL intensity are observed. ECL emission was successfully produced with two sacrificial coreactants (benzoyl peroxide and tri-n-propylamine, TPrA). [4]Helicene DMQA+, [6]helicene DIAZA(Pr/Br)+, and DIAZA(Hex/Br)+ exhibit similar ECL emission wavelength in the near-infrared region and generate very intense ECL signals. Their ECL efficiencies are up to 2.6 times higher than that of the reference compound [Ru(bpy)3]2+ when using TPrA as coreactant. A thermodynamic map gathering both oxidation and reduction potentials and fluorescence data is proposed for the prediction of energy sufficiency needed in both coreactant ECL systems. Such a systematic overview based on the photophysical and electrochemical properties may guide the conception and synthesis of new chromophores with a strong ECL proficiency