“Eggs in egg cartons”: co-crystallization to embed molecular cages into crystalline lattices

Discrete (M3L2)n cages assembled from a tripodal ligand (L) and metal ions (M: Cu(i) or Ag(i)) are embedded in networked coordination hosts formed by partial dissociation of the same discrete cages during the crystallization process. The resulting “eggs-in-an-egg-carton” structures provide unique examples of the co-crystallization of discrete and infinite coordination frameworks.


General information
NMR spectra were measured on a Bruker Avance III HD (500 MHz) spectrometer equipped with a PABBO probe and Bruker AV-500 (500 MHz) spectrometer equipped with a CP-TCI cryoprobe. Melting points were determined on an MPA100 OptiMelt (Stanford Research System) and a Yanaco MP-500V apparatus. High-resolution ESI-MS data were recorded on a Bruker maXis spectrometer (Instrument Center at Institute for Molecular Sciences, Okazaki, Japan). Silica gel chromatography was carried out using Silicagel 60N (Kanto Chemical,neutral,spherical) or Biotage SNAP Ultra cartridge. Solvents and reagents were purchased from TCI, FUJIFILM WAKO Pure Chemical Industries, Sigma-Aldrich (Merck), Combi-Blocks and Kanto Chemical. Unless otherwise noted all of the chemicals were reagent grade and used without any further purification.

Synthesis of ligand 1 and 6
Ligand 1 was prepared according to the previous report [S1] .

Supplementary Figures
(a) (b) (c) Figure S4. Packing structure of 6•7. (a) Two molecules of ligand 6 gearing to form a pair. Here, one ligand 6 (colored as magenta) coordinates to three cages of 7 in the lower layer, while the other (blue) coordinates to those in the upper layer. (b) As described in the main article, ligand 6 cross-links the cage 7 giving 2D sheet-like complex. Note that two face-to-face sheet structures are interlocked as a result of the cross-linking style shown in (a). Among this 'bilayer' structure, helical chirality of cage 7 is same, while that of the neighboring layer is opposite to afford the centrosymmetric crystal packing.
Incubation at 303 K for two weeks gave the crystals (y. 56%). The diffraction data were collected at BL41XU (EIGER X 16 M detector) at SPring-8. The crystals were removed from the microtubes and picked up by the cryo-loop (Hampton), and mounted on a goniometer. Data collection was performed at 100 K.
Single crystals of the co-crystal 6•7 was prepared by slow vapour diffusion of diethyl ether into a CD3NO2 solution prepared from ligand 6 (2.6 mM in nitromethane) and [Cu(MeCN)4]BF4 (3.75 mM) in a glass tube at 276 K. Substantial amount of crystals was obtained after 2 weeks (y. 61%). The crystals were removed from the microtubes and introduced into a glass capillary (borosilicate, Hampton Research), and mounted on a goniometer. The diffraction data were collected at the BL26B1 beamline (EIGER4M (DECTRIS) detector) at the Spring-8. Data collection was performed at 293 K. Diethyleneglycol side chains were severely disordered, thus only the initial several atoms could be assigned. Some of BF4 − ions were also disordered. Phase purity of the crystalline materials was confirmed by screening of the Xray irradiation for (1) several crystals obtained from the same crystallization tube, and (2) different parts on the same crystal with concentrated beam-size, giving identical cell parameters to those finally determined by the main diffraction measurements.