Self-Assembly and Molecular Recognition of a Luminescent Gold Rectangle

A luminescent molecular rectangle [Au4(μ-PAnP)2(μ-bipy)2](OTf)4 (1·(OTf)4) (PAnP = 9,10-bis(diphenylphosphino)anthracene, bipy = 4,4‘-bipyridine, X = NO3- or OTf-), synthesized from the self-assembly of the molecular “clip” Au2(μ-PAnP)(OTf)2 and bipy, shows a large rectangular cavity of 7.921(3) × 16.76(3) Å. The electronic absorption and emission spectroscopy, and electrochemistry of the metallacyclophane, have been studied. The 14+ ions are self-assembled into 2D mosaic in the solid state via complementary edge-to-face interactions between the Ph groups. 1H NMR titrations ratify the 1:1 complexation between 14+ and various aromatic molecules. Comparing the structures of the inclusion complexes indicates an induced-fit mechanism operating in the binding. The emission of 14+ is quenched upon the guest binding. The binding constants are determined by both 1H NMR and fluorescence titrations. Solvophobic and ion−dipole effects are shown to be important in stabilizing the inclusion complexes.