Allosteric Chiral Recognition of Eu(III) Complex for Chiral Co(III) Complex Observed by Time‐Resolved Circularly Polarized Luminescence Spectroscopy

Le résumé fourni par la source

Steady‐state and time‐resolved circularly polarized luminescence (CPL) are investigated for aqueous solutions of [Eu(pda) 2 ] − (pda = 1,10‐phenanthroline‐2, 9‐dicarboxylic acid) containing Δ/Λ‐[Co(en) 3 ] 3+ (en = ethylenediamine). CPL signals (| g lum | ≈ 0.2 at maximum) are observed for the solutions at the f–f transition in [Eu(pda) 2 ] − , where the sign depends on the chirality of [Co(en) 3 ] 3+ . The emission intensity decreases with the increase of concentration of [Co(en) 3 ] 3+ ([Co]). Time‐resolved emission measurements show that the temporal profiles are well reproduced by three emission lifetime components τ 1 ≈ 10 μs, τ 2 ≈ 40‐100 μs, and τ 3 ≈ 100‐750 μs, where the lifetimes depend on [Co]. The shorter lifetimes of τ 1 and τ 2 are attributed to associated species of [Eu(pda) 2 ] − and [Co(en) 3 ] 3+ , in which the energy transfer occurs. The time‐resolved CPL reveals that the τ 1 ‐ and τ 2 ‐components exhibit CPL, but the τ 3 ‐component exhibits no CPL signal. Mole‐ratio dependence of Δ/Λ‐[Co(en) 3 ] 3+ for the CPL signal shows that the CPL is exhibited from two associated species, such as [Eu(pda) 2 ] − ·{[Co(en) 3 ] 3+ } 2 , and the homo‐associated species are favored over hetero‐associated species. This indicates that a structural change induced by initial association of Δ/Λ‐[Co(en) 3 ] 3+ promotes further association of Δ/Λ‐[Co(en) 3 ] 3+ . This is a chiral recognition by allosteric effect.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.