Modulation of Chiroptical and Photophysical Properties in Helicenic Rhenium(I) Systems: The Use of an N‐(Aza[6]helicenyl)‐NHC Ligand

Abstract

The photophysical and chiroptical properties of a novel, chiral helicene-NHCÀ Re(I) complex bearing an N-(aza[6]helicenyl)-benzimidazolylidene ligand are described, showing its ability to emit yellow circularly polarized luminescence. A comparative analysis of this new system with other helicene-Re(I) complexes reported to date illustrates the impact of structural modifications on the emissive and absorptive properties.

Chiroptical activity of benzannulated N-heterocyclic carbene rhenium(i) tricarbonyl halide complexes: towards efficient circularly polarized luminescence emitters

“…Compared to previously reported CPL-emissive Re( i ) complexes, g lum values for the present investigated complexes are twice as low as those recorded for complex ( III ) in Scheme 1, 14 but remarkably, two- to four-fold higher than those reported for complexes ( I )–( II ) and more recently in series ( IV ). 15 The g abs values are overall coherent with previous data, in the 0.5–3 × 10 −3 range (see Fig. S27 of the ESI†).…”

“…[10][11][12] They demonstrated to be of particular interest and suitable for pushing quenching metal centered ( 3 MC) excited states up to higher energies, and enabled preparation of robust and highlyemissive transition metal complexes (TMCs). 13 In this framework, Crassous and co-workers investigated the chiroptical activity of enantiopure tris-carbonyl Re-NHC complexes (I-II), along with the novel longer-lived counterparts bearing the N-(pyridyl)- [5]heliceneimidazolylidene (III), 14 and N-(aza [6]helicenyl)-benzimidazolylidene (IV) 15 helicenic-NHC scaffold as depicted in Scheme 1. A detailed theoretical investigation based on accurate spin-orbit calculations has enabled us to reproduce the experimental CPL spectra and to assign the CPL activity of a series of [ReX(CO) 3 (N^C NHC )] (X = Cl or I; N^C NHC = 1-(2-pyridyl)-4-methylimidazole, 1-(2-pyridyl)-4-methyl-benzimidazole and 1-(2-pyridyl)-2 [4]-helicene-4-methyl-imidazole) complexes as well as to understand the correlation between electronic density character and spin density polarization that control the CPL activity in this class of molecules.…”

1,2,3-Triazol-5-ylidene- vs. 1,2,3-triazole-based tricarbonylrhenium(i) complexes: influence of a mesoionic carbene ligand on the electronic and biological properties

“…It would be instructive to extend the solidstate emission study to other rhenium(I) complexes incorporating various mesoionic and N-heterocyclic carbenes. [15][16][17][18][19][20][21][22][23][24][63][64][65][66][67][68] Finally, one triazolylidene-based complex (Re-T-BOP) showed clear superiority over all other compounds as regards the antibacterial properties. It would be instructive to test the cytotoxicity of this molecule on eukaryotic cells to see if it could be used in therapy.…”

“…[10][11][12][13][14] They emit blue-green to red light in solution at room temperature [15][16][17][18][19][20][21] and have been proposed as efficient circularly polarized luminescence emitters. [22][23][24] According to Massi and co-workers, they exhibit a particular photochemical reactivity 15,16 and can be used as photoinitiators of polymerization upon visible light. 25 Regarding biological applications, these complexes are precursors for radiopharmaceuticals and diagnostic agents.…”

Circularly polarized phosphorescence with a large dissymmetry factor from a helical platinum(ii) complex

“…Helicenes represent a group of compounds in which aromatic rings are helically fused, and are known to exhibit strong chiroptical properties based on their specific helical chirality. [19][20][21] Furthermore, there have been reports of materials exhibiting highly efficient CPP by introducing helicene ligands into Pt(II), [4][5][6]17 Ir(III), 22,23 Re(I) 24,25 and Au(I) 26 centers. The most successful example was reported by Autschbach, Crassous and coworkers in which a platinum(II) complex with a [6]helicene framework exhibited CPP of the order of 10 À2 in the solutiondispersed state at room temperature.…”