Binuclear Complexes Supported by a Tetrapyridyl Ligand with a Bending Anthraquinodimethane Linker

A tetrapyridyl ligand with a bending anthraquinodimethane linker has been synthesized, and its complexation with coinage metals has been examined. The treatment of the ligand with Ag(I) and Au(I) cations afforded binuclear complexes, wherein the two metal centers were in close proximity to the inside space of the ligand. X-ray analyses corroborated with theoretical calculations indicated that the ligand has reasonable flexibility toward a bending deformation of the linker moiety to provide a ligand pocket suitable for the proximal binuclear complexes, even though such deformations accompany a non-negligible amount of energetic cost. On the other hand, treatment with 2 equiv of Cu(I) salt afforded a binuclear complex, in which both copper atoms were coordinated at the periphery of the ligand.