Cationic triangulenes and helicenes: synthesis, chemical stability, optical properties and extended applications of these unusual dyes

Abstract

Cationic triangulenes and helicenes are highly stable carbocations with planar and helical conformations respectively. These moieties are effective dyes with original absorption and emission properties. Over the last decade, they have received greater attention and are considered as valuable tools for the development of innovative applications. In this review, the synthesis of these unique compounds is presented together with their core chemical and physical properties. Representative applications spanning from surface sciences to biology and chemistry are presented.

Slow Magnetic Relaxation in Chiral Helicene-Based Coordination Complex of Dysprosium

“…This is confirmed by the calculated composition of MJ = 0.94 |±15/2> + 0.06 |±11/2> for the ground doublet state of 1 (see Table S5 for the wavefunction composition). The calculated groundstate easy axis (Figure 6) for the Dy III ion is oriented perpendicular to the plane formed by the 2,2′-bipyridine moieties as expected for an oblate ion with this coordination sphere [31,36]. Even if the uniaxiality of the anisotropy is not strictly associated to slow relaxation of the magnetization [46], in most of the cases reported in the literature for Dy III this assumption is valid.…”

“…This is confirmed by the calculated composition of M J = 0.94 |±15/2> + 0.06 |±11/2> for the ground doublet state of 1 (see Table S5 for the wavefunction composition). The calculated ground-state easy axis (Figure 6) for the Dy III ion is oriented perpendicular to the plane formed by the 2,2 -bipyridine moieties as expected for an oblate ion with this coordination sphere [31,36]. …”

“…On the other hand, a 2,2 -bipyridine (bpy) ligand has been functionalized with a [6]-helicene to enhance the luminescence. Indeed, the latter presents a π-conjugated backbone of aromatic rings, configurationally stable for n ≥ 5, and its peculiar topology results in intense emission [31,32]. Moreover, [n]-helicene ligands are helically-shaped, so they possess a chirality despite the absence of enantiocenter.…”

Azadioxatriangulenium: Synthesis and Photophysical Properties of Reactive Dyes for Bioconjugation

“…ADOTA is a triangulenium dye, [6] a group of cationic fluorescent dyes with unique properties. [7] One characteristic property of the ADOTA chromophore is the rare combination of relatively low oscillator strengths of the emissive transition and high fluorescence quantum yields, which gives rise to fluorescence lifetime of 10 – 20 ns, despite the relatively low energy gap between the ground state and the first excited state.…”

Electronically Stabilized Nonplanar Phenalenyl Radical and Its Planar Isomer

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] These compounds are of great fundamental interest and yet they also have a range of potential applications in photochemistry, 14,15 synthesis, 16,17 materials science, 18-21 spintronics [22][23][24] and biology. 25,26 In particular, open-shell polycyclic aromatic hydrocarbons have been shown to be promising molecular conductors and spin carriers in the emerging field of organic spin chemistry.…”