Efficient Annihilation Electrochemiluminescence of Cationic Helicene Luminophores

Abstract

The electrochemistry and annihilation electrochemiluminescence (ECL) of a series of chiral cationic helicene luminophores containing various substituents were investigated in acetonitrile solvent. The electrochemical characterization evidenced a systematic reversible reduction of cationic derivatives, whereas the oxidation could be reversible or not, depending on the nature of the core heteroatoms within the structure as well as the functional-group appendages. One of the key parameters governing the ECL intensity is, indeed, the formal redox potentials for the electrogeneration of the neutral radical and dication radical species, which will undergo the annihilation reaction. On that basis, a thermodynamic wall of efficiency was proposed in the case of ECL annihilation pathway to predict the formation efficiency of the emitting excited state and, eventually, the light emission's strength. This very simple wall is constructed by plotting the difference of formal potentials in function of the fluorescence wavelength, thus delimiting two domains where ECL is thermodynamically possible or unfavorable.

Ion Transfer Voltammetry in Polyurethane Thin Films Based on Functionalised Cationic [6]Helicenes for Carbonate Detection

“…The procedures for the preparation of dioxa + [6]helicene, dipropyl and dioctyl diaza + [6]helicenes (diaza + (C 3 ) 2 and diaza + (C 8 ) 2 , respectively) have been previously reported . These derivatives were synthesized in one step from a single common advanced synthetic intermediate (See Figure S1 for structural and synthetic information) . Regioselective bromination and nitration of the dioctyl derivative afforded the diaza + (C 8 ) 2 Br 2 and diaza + (C 8 ) 2 (NO 2 ) 2 moieties, respectively .…”

“…The electrochemical properties of cationic [6]helicenes can be modulated by the nature of the heteroatoms (O, N) contained within the helical core or via the addition of peripheral substituents . The study on cationic [6]helicenes as a molecular redox probes for thin voltammetric films described earlier for the detection of cations is extended here to anions.…”

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).…”

Photophysical and Electrochemiluminescence of Coumarin‐Based Oxazaborines

“…However, the scarcity and high cost of the so‐called platinum groups metals requires searching for alternatives. In this context, polycyclic aromatic hydrocarbons are promising options despite their lower intrinsic solubility in water …”