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Helicene Bis(pyrazol-1-yl)pyridine Ligands for Luminescent Transition-Metal Complexes

Abstract : We describe herein the synthesis of 2,6‐bis(pyrazol‐1‐yl)pyridine (1‐bpp) ligands substituted by helicene units in the 4‐position of the pyridine ring. The two‐step procedure afforded the molecules bpp[n]helicene (n = 4, 5 and 6) and methyl‐bpp[4]helicene, abbreviated as 4, 5, 6 and 4m respectively, with overall good yields. This series of ligands shows fluorescence in the violet region, with a red shift of the emission when increasing the number of aromatic rings in the helicene unit. The tridentate fluorophores have been reacted with Re(CO)5Cl and [Ru(terpy)Cl3] to prepare a series of transition metal complexes formulated as [ReI(n)(CO)3Cl] (n = 4 and 5) and [RuII(n)(terpy)](PF6)2 (n = 4, 4m, 5 and 6). The compounds [ReI(4)(CO)3Cl]·(CH2Cl2)0.5(H2O) and [RuII(4m)(terpy)](PF6)2 crystallized in the centrosymmetric space groups P21/n and P1 respectively, and thus present both M and P helicene units in their crystal structures. The absorption and emission properties of the complexes have been studied. All complexes show luminescence at 77 K in frozen DCM solution. The tricarbonyl complex [ReI(5)(CO)3Cl] shows a strong emission band with two peaks at 540 nm and 580 nm, which could be attributed to ligand‐localized π–π* phosphorescence due to the extended π system of the ligand. The heteroleptic RuII complexes show emission bands above 600 nm attributed to the terpyridine‐based 3MLCT state.
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Soumis le : lundi 30 novembre 2020 - 13:58:48
Dernière modification le : mardi 1 décembre 2020 - 14:37:20
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Alexandre Abhervé, Kevin Martin, Andreas Hauser, Narcis Avarvari. Helicene Bis(pyrazol-1-yl)pyridine Ligands for Luminescent Transition-Metal Complexes. European Journal of Inorganic Chemistry, Wiley-VCH Verlag, 2019, 2019 (45), pp.4807-4814. ⟨10.1002/ejic.201900870⟩. ⟨hal-02469020⟩



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