Self-assembly and molecular recognition of a luminescent gold rectangle

A luminescent molecular rectangle [Au-4(mu-PAnP)(2)(mu-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" Au-2(mu-PAnP)(OTf)(2) and bipy, shows a large rectangular cavity of 7.921(3) x 16.76(3) Angstrom. The electronic absorption and emission spectroscopy, and electrochemistry of the metallacyclophane, have been studied. The 1(4+) ions are self-assembled into 2D mosaic in the solid state via complementary edge-to-face interactions between the Ph groups. H-1 NMR titrations ratify the 1:1 complexation between 1(4+) 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.