Self-assembly and molecular recognition of a luminescent gold rectangle

Abstract

A luminescent molecular rectangle [Au4(u-PAnP) 2(u-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(u-PAnP)(OTf) 2 and bipy, shows a large rectangular cavity of 7.921(3) x 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.