A biphenyl-bridged bis(cyclen) cyclophane: Ag(I)-induced conformational reorganization and successive Ag(I) binding.

A biphenyl-bridged bis(cyclen) cyclophane L containing two argentivorous Ag(I)-binding sites was synthesized, and its Ag(I)-binding behavior was investigated in the solid state and in solution. Single-crystal X-ray diffraction and spectroscopic studies showed a pronounced Ag(I)-induced conformational reorganization from an open free-ligand structure to a compact, helically wrapped di-Ag(I) complex, while NMR, CSI-MS, and equilibrium analysis showed that the mono-Ag(I) intermediate does not accumulate substantially. These results suggest that conformational reorganization accompanying the first Ag(I)-binding event may facilitate subsequent uptake of the second Ag(I) ion.