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Chiral Molecular Ruby [Cr(dqp)2]3+ with Long-Lived Circularly Polarized Luminescence

Cruz, Carlos M.
Cuerva, Juan M.
Campaña, Araceli G.
Published in Journal of the American Chemical Society. 2019, vol. 141, no. 33, p. 13244-13252
Abstract The chiral resolution of a kinetically inert molecular ruby [Cr(dqp)2]3+ (1, dqp = 2,6-di(quinolin-8-yl)pyridine) displaying strong dual light emission at room temperature has been achieved. The wrapped arrangement of the sixmembered dqp chelating ligands around the Cr(III) provided non-planar helical conformations leading to the diastereoselective assembly of chiral bis-tridentate monometallic Cr(III)-helix. The PP‐(+)-[Cr(dqp)2]3+ and MM-(-)- [Cr(dqp)2]3+ enantiomers could be separated and isolated by using cation-exchange chromatography and subsequent saltmetathesis with KPF6. X-Ray crystallographic analysis based on Flack parameters assigned the absolute configurations of the two enantiomers. Circularly Polarized Luminescence (CPL) spectra showed two polarized emission bands within the NIR region corresponding to the characteristic metal-centered spin-flip Cr(2E→4A2) and Cr(2T1→4A2) transitions with exceptionally high dissymmetry factors, glum, of 0.2 and 0.1, respectively, which are comparable to those reported for rareearth chiral complexes. Photophysical properties also revealed an extremely long excited-state lifetime of 1.2 ms and a high quantum yield of 5.2% at room temperature in water. These properties make [Cr(dqp)2]3+ an ideal sensitizer for the preparation of enantiopure luminescent supramolecular energy-converting devices and also open up the possibility of using chiral Cr(III) chromophores for the construction of NIR-CPL materials and polarized photonic devices based on earthabundant metals.
Keywords ChromiumChiralLuminescenceEmitterCPL
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Research group Groupe Piguet
Project FNS: 200020_179758
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JIMENEZ, Juan et al. Chiral Molecular Ruby [Cr(dqp)2]3+ with Long-Lived Circularly Polarized Luminescence. In: Journal of the American Chemical Society, 2019, vol. 141, n° 33, p. 13244-13252. doi: 10.1021/jacs.9b06524 https://archive-ouverte.unige.ch/unige:122438

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Deposited on : 2019-09-02

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