Chiral Emissive Lanthanide Complexes from Enantiopure [6]Helicene‐bis(pyrazolyl)‐pyridine Ligands

Abstract

Enantiopure helicene‐based bis(pyrazol‐1‐yl)pyridine (bpp‐[6]helicene), with the helicene unit in position 4 of the pyridine ring, have been prepared and structurally characterized. Their chiroptical properties have been studied experimentally, and both absorption and circular dichroism (CD) spectra have been reproduced theoretically by time‐dependent density functional theory (TDDFT). Remarkably, in spite of the remote localization of the helicene with respect to the coordination pocket of the bpp motif, chiral Eu(III) complexes based on these ligands show, however, circularly polarized luminescence in the visible region, sustained by TDDFT and CASSCF calculations, which also emphasize the possible antenna effect of the bpp ligand.

Multifunctional Helicene‐Based Ytterbium Coordination Polymer Displaying Circularly Polarized Luminescence, Slow Magnetic Relaxation and Room Temperature Magneto‐Chiral Dichroism**

“…However, generating helicene‐based metal‐organic 1D polymeric architectures remains challenging and very few examples are described in the literature [35] . Recently, we have shown that 3‐(2‐pyridyl)‐4‐aza[6]‐helicene (H6bpy) bearing a 2,2′‐bipyridine coordinating unit can accommodate a lanthanide ion and combine the inherent properties of the helicenic ligand with those of the lanthanide to create unprecedented chiral SMMs ( 1 ) (Figure 1a), [36–39] efficient singlet oxygen sensitizers, [40] and strong MChD response in the NIR range of the electromagnetic spectrum [41–43] . Despite their pertinent chiroptical properties, chiral emissive Yb III complexes are still scarce [18, 19, 44–49] .…”

“…[35] Recently, we have shown that 3-(2-pyridyl)-4-aza [6]-helicene (H6bpy) bearing a 2,2'-bipyridine coordinating unit can accommodate a lanthanide ion and combine the inherent properties of the helicenic ligand with those of the lanthanide to create unprecedented chiral SMMs (1) (Figure 1a), [36][37][38][39] efficient singlet oxygen sensitizers, [40] and strong MChD response in the NIR range of the electromagnetic spectrum. [41][42][43] Despite their pertinent chiroptical properties, chiral emissive Yb III complexes are still scarce. [18,19,[44][45][46][47][48][49] Herein, we describe the synthesis of the first homochiral monodimensional coordination polymer (1D-CP), namely M-and P-[H6(py) 2 Yb(hfac) 3 ] n 2 and its structural features.…”

Multifunctional Helicene‐Based Ytterbium Coordination Polymer Displaying Circularly Polarized Luminescence, Slow Magnetic Relaxation and Room Temperature Magneto‐Chiral Dichroism**

“… [35] Recently, we have shown that 3‐(2‐pyridyl)‐4‐aza[6]‐helicene (H6bpy) bearing a 2,2′‐bipyridine coordinating unit can accommodate a lanthanide ion and combine the inherent properties of the helicenic ligand with those of the lanthanide to create unprecedented chiral SMMs ( 1 ) (Figure 1a ),[ 36 , 37 , 38 , 39 ] efficient singlet oxygen sensitizers, [40] and strong MChD response in the NIR range of the electromagnetic spectrum. [ 41 , 42 , 43 ] Despite their pertinent chiroptical properties, chiral emissive Yb III complexes are still scarce. [ 18 , 19 , 44 , 45 , 46 , 47 , 48 , 49 ] Herein, we describe the synthesis of the first homochiral monodimensional coordination polymer (1D‐CP), namely M ‐ and P ‐[H6(py) 2 Yb(hfac) 3 ] n 2 and its structural features.…”

Asymmetric Lumino-Transformer: Circularly Polarized Luminescence of Chiral Eu(III) Coordination Polymer with Phase-Transition Behavior

“…A series of Eu­(III) complexes with chiral organic ligands, such as camphor, Pybox, naphthol, and helicene derivatives, have been reported. ,− The CPL properties of chiral Eu­(III) complexes are closely related to their coordination geometries and structural strain of ligands. Yuasa demonstrated that the cis – trans isomerization of the bidentate phosphine oxide ligand in a chiral Eu­(III) complex leads to CPL sign inversion .…”