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.