Issue 13, 2024

Programming heterometallic 4f–4f′ helicates under thermodynamic control: the circle is complete

Abstract

Three non-symmetrical segmental ligand strands L4 can be wrapped around a linear sequence of one Zn2+ and two trivalent lanthanide cations Ln3+ to give quantitatively directional [ZnLn2(L4)3]8+ triple-stranded helicates in the solid state and in solution. NMR speciations in CD3CN show negligible decomplexation at a millimolar concentration and the latter helicate can be thus safely considered as a preorganized C3-symmetrical HHH-[(L43Zn)(LnA)(2−n)(LnB)n]8+ platform in which the thermodynamic properties of (i) lanthanide permutation between the central N9 and the terminal N6O3 binding sites and (ii) exchange processes between homo- and heterolanthanide helicates are easy to access (Ln = La, Eu, Lu). Deviations from statistical distributions could be programmed by exploiting specific site recognition and intermetallic pair interactions. Considering the challenging La3+ : Eu3+ ionic pair, for which the sizes of the two cations differ by only 8%, a remarkable excess (70%) of the heterolanthanide is produced, together with a preference for the formation of the isomer where the largest lanthanum cation lies in the central N9 site ([(La)(Eu)] : [(Eu)(La)] = 9 : 1). This rare design and its rational programming pave the way for the preparation of directional light-converters and/or molecular Q-bits at the (supra)molecular level.

Graphical abstract: Programming heterometallic 4f–4f′ helicates under thermodynamic control: the circle is complete

Supplementary files

Article information

Article type
Paper
Submitted
29 Feb 2024
Accepted
29 Feb 2024
First published
01 Mar 2024
This article is Open Access
Creative Commons BY license

Dalton Trans., 2024,53, 6050-6062

Programming heterometallic 4f–4f′ helicates under thermodynamic control: the circle is complete

C. Egger, L. Guénée, N. Deorukhkar and C. Piguet, Dalton Trans., 2024, 53, 6050 DOI: 10.1039/D4DT00610K

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