Fig. 1: The ClickZip principle and metal ion preferences.

A Chelator PhL¹ acts as an irreversible molecular trap for Ln^III ions in two steps: (1) binding the Ln^III ion in a conventional and reversible complexation step; and (2) trapping the Ln^III ion by irreversible formation of an intramolecular 1,5-triazole bridge that cross-links the two pyridine pendant arms, resulting in a cryptate-type chelate, Ph{Ln}. The whole process runs as one-pot procedure without isolation of the [Ln(PhL¹)] intermediate. B, C Percentage of different species formed during the ClickZip process as a function of the metal and time. Conditions: 0.5 mM PhL¹ and 1.0 mM Ln^III salt (including Y^III and Sc^III) in 50 mM aq. MOPS/NaOH buffer (pH 7.0) at 80 °C (except for column L, where no metal was added). Analysis: HPLC with UV detection at λ = 280 nm (further details in Supplementary Fig. 3). Starting purity of PhL¹ prior to the experiment is labelled as CONTROL (details about PhL¹ stability in Supplementary Fig. 4). Identified species are colour-coded as shown in the legend, with all other detected species jointly shown in red. B Results after 1 h at 80 °C. The efficacy of ClickZip increases from largest La^III ion to smallest Lu^III ions. Note that the fastest Ph{Lu} is already formed with 65% conversion, while very little conversion to any product is observed for sample without any Ln^III (column L). The corresponding intermediates [Ln(PhL¹)] are susceptible to acid hydrolysis during HPLC analysis (0.1% FA additive used in the mobile phase, pH ~2.8) and therefore some fraction of [Ln(PhL¹)] is detected as PhL¹. C Results after 1 week at 80 °C. High conversion is achieved even for the slower-reacting Ln^III ions ( ≥ 85% from Sm^III to Lu^III and Y^III), with low amounts of side-products (red bar). The efficacy of ClickZip is low for metal ions that are too large (La^III to Nd^III) or too small (Sc^III), yet the corresponding Ph{Ln} can still be isolated (except for very labile Ph{Sc}). The reaction without any Ln^III (column L) provides a mixture of products. Identified side-products include PhL¹-MOPS adduct (see Supplementary Fig. 4), Ca^II chelate Ph{Ca}, and empty cages (1,4-cz-PhL¹ and 1,5-cz-PhL¹). Source data available in Supplementary Data 2.