Self-Assembled M 2 L 4 Nanocapsules: Synthesis, Structure and Host-Guest Recognition Toward Square Planar Metal Complexes †

Metallosupramolecular cages of the general formulas [M 2 (L) 4 ][X] 4 can be self-assembled in good yields, where M = Pd, X = NO 3 , L = L 1 (1a); M = Pd, X = OTf, L = L 1 (1b); M = Pt, X = OTf, L = L 1 (2); M = Pd, X = OTf, L = L 2 (3); L 1 = 1,3-bis(pyridin-3-ylethynyl)-5-methoxybenzene; and L 2 = 2,6-(pyridin-3-ylethynyl)-4-methoxyaniline, respectively. These cages have been fully characterized using 1 H, 13 C NMR, elemental analysis, IR spectroscopy, and electrospray mass spectrometry. Additionally the molecular structure of [Pd 2 (L 1) 4 ][OTf] 4 (1b) was confirmed using single crystal X-ray diffraction. The capacity of central cavities of M 2 L 4 cages to accommodate square planar metal complexes was investigated. In particular, the tetracationic cage [Pd 2 (L 2) 4 ][OTf] 4 (3) was found to encapsulate the anionic metal complex [PtCl 4 ] 2− through electrostatic interactions and also via hydrogen bonding with the amino groups of the bridging ligand displayed by this nanocage.