Several  novel and reported octahedral [Pd₆L₁₂]¹²⁺ and [Pd₆L₈]¹²⁺-type coordination cages were synthesized (Figure 1a). Both, their thermodynamic and kinetic stability were investigated by subjecting cage solutions to different concentrations of pyridine in DMSO or acetonitrile. The cage degradation was monitored by ¹H NMR. Thermodynamic stability was quantified using Dpy₅₀ values, the number of equivalents of pyridine at which 50 % of the cages are remain intact at equilibrium. For kinetic stability, the half-lives (t_1/2) were determined for various pyridine concentrations. The thermodynamic stability of the cages varies by nearly two orders of magnitude and the kinetic stability over four orders of magnitude (Figure 1b). The stability of the cages was primarily governed by the nature of the donor group, topicity playing a subordinate role. Additionally, we show that kinetically trapped imidazole-based cages can be enriched by precipitation and crystallized. Notably, we report for the first time the crystal structure of a [Pd₈L₁₆]¹⁶⁺-type cage.

[1] Jean de Montmollin, Atena B. Solea, Damien W. Chen, Farzaneh Fadaei-Tirani and Kay Severin, Inorg. Chem., 2024, 63, 4583-4588.

[2] Ru-Jin Li, Jean de Montmollin, Farzaneh Fadaei-Tirani, Rosario Scopelliti and Kay Severin, Dalton Trans., 2023, 52, 6451-6456.